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Senior Independent Study Theses

2013

Exploring the Microhabitats of Marsupial Frogs: aStudy of the Forces Driving Habitat Selection ForFlectonotus Fitzgeraldi Within HerbaceousXanthosoma Jacquinii Populations of TobagoMeredith M. EyreThe College of Wooster

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© Copyright 2013 Meredith M. Eyre

Recommended CitationEyre, Meredith M., "Exploring the Microhabitats of Marsupial Frogs: a Study of the Forces Driving Habitat Selection For FlectonotusFitzgeraldi Within Herbaceous Xanthosoma Jacquinii Populations of Tobago" (2013). Senior Independent Study Theses. Paper 4954.http://openworks.wooster.edu/independentstudy/4954

EXPLORING THE MICROHABITATS OF MARSUPIAL FROGS: A STUDY OF THE FORCES DRIVING HABITAT SELECTION FOR

FLECTONOTUS FITZGERALDI WITHIN HERBACEOUS XANTHOSOMA JACQUINII POPULATIONS OF TOBAGO

DEPARTMENT OF BIOLOGY

INDEPENDENT STUDY THESIS

Meredith Milo Eyre

Advisor: Richard Lehtinen and Marilyn Loveless

Submitted in Partial Fulfillment of the Requirement for

Independent Study Thesis in Biology at the

COLLEGE OF WOOSTER 2013

TABLE OF CONTENTS

I. TITLE PAGE

II. TABLE OF CONTENTS 1

III. ABSTRACT 2

IV. INTRODUCTION 3

V. METHODS 16

VI. RESULTS 32

VII. DISCUSSION 37

VIII. ACKNOWLEDGEMENTS 54

IX. LITERATURE CITED 55

X. APPENDIX 61

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ABSTRACT

This study explored the forces driving habitat selection for a little-known

phytotelm-dwelling tropical marsupial frog, Flectonotus fitzgeraldi (Hylidae), among

phytotelms in the herbaceous Xanthosoma jacquinii (Araceae). Data were collected on

the Caribbean island of Tobago from July 27th to August 3rd, 2012. In order to better

define the frog’s ecological niche, I examined 106 X. jacquinii, of which 11 were

occupied by frogs. Data were collected for environmental variables (canopy cover,

detritus, invertebrate presence, distance to nearest neighboring plants), morphological

characteristics of the plant (height, diameter, length of the longest petiole and leaf,

number of leaf axils), and aquatic variables for the phytotelms within the plants

(dissolved oxygen concentration, temperature, pH, and water depth). A Multiple Logistic

Regression Model found that water depth was the only significant predictor of F.

fitzgeraldi occupancy in X. jacquinii phytotelms (p=0.023). Therefore, the frog species

seems to have a relatively broad ecologic niche based on its ability to withstand a large

range of ecological conditions. This flexibility may allow the frog to occupy other types

of phytotelms including tree holes, bamboo stumps, bromeliads, or phytotelms created by

other plants as long as the microcosm provides an adequate water supply. From a

conservation perspective, this provides hope for the frog’s long term survival despite

possible changes to surrounding environmental or ecological conditions.

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INTRODUCTION

The field of ecology has developed tremendously in recent years as old theories

are reexamined, new experimental techniques are created, and basic ecological ideas shift

based on new insight. One such concept, the ecological niche, has been redefined many

times over the years. This concept is essential to understand because it is always

intimately linked with at least one of several other major themes in ecology including an

organism’s behavior, morphology, or physiology. In addition, the niche concept provides

insight into how the individual or species functions within its larger community,

specifically with respect to competitor, predator, or prey interactions and resource use.

Therefore, it is a very important concept to define clearly, as it puts other ecological ideas

and theories into a larger context. By fully understanding the niche of a species, one may

ultimately be able to predict distribution or abundance patterns for the species. This

information may be essential to future conservation efforts.

The original description of the niche was focused on understanding the

environmental requirements necessary for the long-term survival and reproduction of an

individual or species (Grinnell 1917). By this theory, the characteristic nature of an

organism’s habitat is the most important factor in determining how an organism or

species fits into the complex ecological web in which it lives. For example, a habitat

comprised mainly of underbrush is essential to the California thrasher because this

structure provides the bird with a place to breed and escape predators in addition to

serving as a source of food. Therefore, characteristics of an individual’s habitat play an

integral role in both the general behavior and long-term survival of the species.

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Grinnell’s definition of an ecological niche is based on this habitat description. This

niche concept may be used to explain both the behavior of a single individual or

characteristic behavioral patterns of an entire species.

Hutchinson (1957) also developed the niche concept farther by introducing the

idea of a “fundamental” and “realized” niche. A species’ fundamental niche describes

the widest possible range of conditions the individual or species may tolerate (Hutchinson

1957). Historically, biologists have focused considerable time and energy into

determining the factors that contribute to the fundamental niche of an organism.

However, selective pressures may force the species to inhabit a smaller range of

conditions. For example, Robert Paine (1966) studied this phenomenon in the mussel

species Mytilus californianus growing along the shorelines of western North America.

The mussel species grows in a well-defined band in the rocky intertidal zone. This band

of mussels is bordered at its base by a series of predators including the starfish Pisaster

ochraceus. When Pisaster was removed manually, the mussels advanced downward to

inhabit the newly exposed surface relatively quickly. Thus, it can be concluded that even

though M. californianus and P. ochranceus occupy similar ecological niches, the mussels

are forced to only occupy a fraction of their fundamental niche because the starfish will

out-compete any mussels that try to grow into the starfish’s overlapping habitat.

Therefore, the band of intertidal zone that M. californianus occupies represents its

realized niche. Thus, the realized niche is comprised of the smaller range of conditions

the organism is actually able to occupy given the surrounding biotic interactions

(Hutchinson 1957).

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The distinction between the fundamental and realized niche revolutionized the

niche concept into a more quantifiable measurement based on Hutchinson’s (1957)

mathematical model. This model quantitatively illustrates the smaller realized niche

compared to the full range of conditions the organism could potentially tolerate

comprising the fundamental niche. In this model, each environmental variable is

represented along an axis to illustrate the full range of conditions in which the individual

has the ability to function. For example, this continuum may represent the range of

temperature or resources an individual may withstand. Because each condition is

represented by an axis, the fundamental niche is defined as “a region of an n-dimensional

hypervolume” (Hutchinson 1957). However, interspecific interactions restrict a species

to a fraction of its larger potential. Thus, the realized niche may be depicted

mathematically as a fraction of this larger fundamental niche.

In addition to defining an ecological niche by habitat characteristics and resource

needs, the term has also been used to describe the role of an organism in a community

especially with regard to food consumption (Elton 1927, MacArthur and Levin 1967).

Specifically, Elton (1927) used the term to describe the placement of a species within a

community’s food web. By this definition, Elton observed that arctic foxes and spotted

hyenas occupy very similar niches. The arctic fox eats the eggs of guillemots seasonally,

while relying on the remains of seals killed by polar bears year-round. Similarly, the

spotted hyena relies on the remains of zebras killed by lions year-round, while

supplementing its diet with large numbers of ostrich eggs seasonally. Because the arctic

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fox and spotted hyena have parallel roles in their community structure, by Elton’s

definition, their ecological niche is essentially the same.

Both Grinnell’s habitat and resource based definition and Elton’s ecological role

based definitions are critical to understanding how an individual or species fits into a

larger community structure and survives long-term in its environment. These definitions

were integrated with the emergence of the competitive exclusion principle, stating that

two competing species must differ in several traits related to their fitness in order to

coexist (Hardin 1960). For example, two species may live within the same habitat

directly in contact with each other, but as long as they have a different role in the food

web, they may coexist. Conversely, the long term survival of two species with identical

ecological roles is not threatened as long as they live in different habitats. This

competitive exclusion principle is based on the assumption that one species will

inevitably out-compete the other species for key resources, eventually forcing it out of the

habitat. However, two species with differing resource requirements and ecological roles

may coexist because each occupies a separate ecological niche within the same

ecosystem.

Because the niche concept is fundamentally integrated into so many aspects of

ecology, it has been used in many ecological papers over the years, often to the point of

confusing its meaning. Chase and Leibold (2003) attempted to redefine the niche concept

with the following definition: “an ecological niche is the joint description of the

environmental conditions that allow a species to satisfy its minimum requirements so that

the birth rate of a local population is equal to or greater than its death rate along with the

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set of per capita effects of that species on these environmental conditions.” This

definition incorporates both historical perspectives of the ecological niche concept,

essentially combining Grinnell’s resource use definition with Elton’s ecological role

definition. This niche definition may be used in the context of a single organism or an

entire species.

An organism’s mobility or lack thereof plays a crucial role in establishing its

ecological niche. Organisms that are immobile are limited to a single geographic location

and are forced to face the challenges of the environment without moving to avoid harsh

conditions. Thus, plants have developed a wide range of morphological characteristics in

response to the challenges being immobile present. This has resulted in both the

speciation of entire new lineages and phenotypic plasticity of individual plants. In

contrast, mobile organisms have the ability to actively select their habitats and move in

response to environmental stimuli. Individuals that inhabit areas that promote their

survival and reproduction have a clear evolutionary advantage. Furthermore, the

individuals that inhabit less suitable environments will leave fewer offspring (Southwood

1988). Because an organism’s habitat is crucial to its survival and reproduction, it makes

sense for a species to evolve mechanisms that allow its members to perceive and respond

to their environments accordingly. Therefore, evolutionary adaptations that allow for

habitat selection play a crucial role in determining the future success of the species

(Southwood 1988, Holt 1987, Murphy 2003).

Habitat selection, or the concept that individuals are able to choose to occupy the

habitat in which their fitness is greatest, represents another fundamental theme in ecology

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(Rosenzweig 1991). The term is used to refer to a set of behavioral responses that may

result in the disproportionate use of habitats, ultimately influencing the survival and

fitness of individuals (Jones 2001, Hutto 1985, Block and Brennan 1993). Habitat choice

is demonstrated in, but not limited to, several species of insects, lizards, rodents, and

birds (Rausher 1984, Brown 1998, Hanski and Singer 2001, Odling-Smee et al. 2003).

These studies have shown that organisms move in response to a wide variety of

conditions including resource needs, biotic factors, and environmental variables.

Because of the range of habitats mobile organisms experience, some evolutionists believe

that habitat selection by individuals may channel the direction of adaptive evolution

(Rosenzweig 1987, Holt 1987). Thus, organisms are not simply at the mercy of their

environment, dependent on the limits of their physiology. Instead, mobile organisms

actively play a role in determining their long-term survival by learning how to respond to

environmental cues and develop habitat selection techniques. Previous analyses have

focused primarily on alleles, genotypes, and phenotypes that influence habitat or resource

choice by examining movement patterns for organisms in heterogeneous environments

(Krebs et al. 1978, Stephens and Krebs 1986).

The term “habitat selection” implies that complex behavioral patterns are

understood by biologists on some level (Cherrett 1989). In contrast, “habitat use” simply

refers to the way an organism uses a collection of physical and biological entities in a

habitat (Krausman 1999). Therefore, the distribution pattern of individuals is the end

result of the habitat selection process (Jones 2001, Cherrett 1989). In order to confidently

conclude that habitats have been selected, an important aspect of habitat selection must

-­‐9-­‐    

be met: individuals within the study species must demonstrate the ability to make

decisions about their surroundings. The resulting habitat use may be described and

explained through the analysis of the costs and benefits associated with certain habitat

characteristics. A disproportional use of potential habitats corresponding with these

quality assessments provides evidence for this active habitat selection (Fretwell and

Lucas 1970, Jones 2001). Therefore, understanding patterns in overall habitat quality is

essential in determining if the individual has actively selected its habitat. It is important

to remember that without behavioral or life history information, there is no way to know

if the detected differences in habitat characteristics actually have any direct influence on

the choice of the individual (Jones 2001, Martin 1992, Martin 1998). However, even if

the individual’s resulting fitness is not fully understood, it is still assumed to be adaptive

on some level (Jones 2001, Robertson 1972, Pulliam and Danielson 1991, Martin 1998).

Ultimately, a compromise must be made when assessing the quality of the habitat.

Knowledge of how each environmental factor affects a species must be balanced with

inferred predictions based on observations of similar species (Jones 2001).

Jones’ (2001) study states that habitat selection may result in the disproportionate

use of habitats. Although not the sole evidence for habitat selection, this disproportionate

use of potential habitats based on the quality of habitat may serve as evidence for habitat

selection. Instead of individuals being evenly distributed throughout their entire potential

range, they may be found in larger numbers in a subsection of this habitat. If

characteristics of this smaller habitat prove beneficial to the individual, it may support the

theory that habitats are actively being selected. The ideal free distribution theory further

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explains this observation (Cherret 1989 pg. 327). This theory is a widely discussed

model that helps predict where animals will be distributed within the environment, based

on the assumption that all the mobile animals are free and able to travel wherever they

like. In addition, it is also assumed that the organisms each have a perfect knowledge of

every habitat within the larger ecosystem. According to this theory, a relatively equal

distribution of species will spread evenly throughout the entire potential range of the

species (Fretwell and Lucas 1970). As the highest quality environments become too

densely populated, their overall quality decreases until their quality matches the

previously unoccupied habitats. At this point, the previously unoccupied habitats become

filled from the overflow of organisms from the more densely populated habitats.

Eventually, a relatively equal distribution of species will result, spread evenly throughout

the habitats of equal quality. Therefore, the disproportional distribution of individuals

throughout the larger range of the species provides evidence that habitat selection has

occurred.

There is a fitness advantage in being able to perceive and respond to certain

environmental cues. However, it is difficult for biologists to recognize and prioritize

which biotic or abiotic conditions contribute most to the quality of a habitat. Examining

the effects of these conditions on an individual’s behavior or physiology is difficult on a

large scale because the individual must respond to both a variety of conditions at once

and a range within each condition (Brown et al. 1996). Therefore, a biologist may spend

years assessing the characteristics of an organism’s habitat, only to find that nothing more

than broad observations may be made because the animal roams a large area of land that

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encompasses a wide variation in environmental factors. For example, researchers

observed broad patterns that could be used to describe the habitat selected by Asian

elephants. The study found these elephants preferred a dense shrub layer, shorter trees, a

dense canopy, and smaller trunk radii (Limin and Li 2005). However, it would be very

difficult to confidently conclude that tree height alone affects the habitat of the elephants,

as the elephant’s natural range incorporates a large range of tree heights in addition to the

multitude of other factors. Since these organisms move over a large spatial scale, it

would be nearly impossible logistically to quantify and identify all aspects of the

environment that may play a role in habitat choice (Limin and Li 2005). In fact, some

species may require different types of habitats and conditions over the course of their

lifetime. Ultimately, a combination between both biotic and abiotic factors determines

the quality of an organism’s habitat (Heying 2004). Therefore, although each factor may

contribute either positively or negatively to the fitness of the individual, it is often

difficult to specify which factors are most important to an organism’s success.

However, the complex system may be simplified by focusing on a smaller spatial

scale (Lehtinen et al. 2004). Some mobile organisms may spend the majority of their life

living within a self-contained microcosm. Although microcosms may be difficult to

locate in the field, they may be easily and thoroughly observed upon discovery (Lehtinen

et al. 2004). Because of their discrete nature, microcosms serve as model systems for

studying the characteristics of the habitat these mobile organisms inhabit. Each

microcosm may be studied on a very small scale to precisely determine the biotic,

chemical, and physical characteristics affecting the system (Srivastava et al. 2004,

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Lehtinen et al. 2004). Furthermore, most factors measured will be homogenous

throughout the entire system. Therefore, a more holistic assessment of the habitat that

directly affects the individual is possible. This may provide insight into how mobile

organisms living within microcosms respond to both biotic and abiotic challenges and

utilize the surrounding environment. Microcosms also provide a clear logistical

advantage in that many replicates may be sampled per unit time, thus increasing the

sample size within a study.

Species that inhabit phytotelmata are a prime example of organisms that inhabit

microcosms (Lehtinen et al. 2004, Summers and McKeon 2004). A phytotelm is a body

of water contained entirely within a plant (derived from Greek: phytos=plant, telm=pond)

(Lehtinen et al. 2004). There are many different types of phytotelmata including water-

filled tree holes, bamboo stumps, bromeliad tanks, nut husks, tree buttresses, and leaf

axils (Lehtinen et al. 2004, Silva et al. 2011, Lin and Kam 2008, Chiu and Kam 2006,

Kam et al.1996). The volume of water in these different microcosms may range in size

from several milliliters (Rödel et al. 2004) to tens or hundreds of liters (Schiesari et al.

2003).

Phytotelmata may be used for breeding, feeding, resting, and water-balance for a

variety of species in the tropics (Lehtinen 2002). For example, water-filled axils in screw

pines (Pandanus) were shown to provide microhabitats for 20 different species of reptiles

and amphibians in Madagascar (Lehtinen 2002). In addition, past research has indicated

that there are at least 102 species of phytotelm-breeding frogs, representing at least 2% of

all recognized frog taxa (Lehtinen et al. 2004).

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A phytotelm presents a unique set of benefits and challenges to the individual

inhabiting it (Lehtinen 2004, Silva et al. 2011, Lehtinen and Carfagno 2011). Although

these microcosms are thought to be relatively safe from the predators and competitors

often present in larger ponds or streams, the unique microhabitat is not necessarily a safe

haven (Caldwell and Araujo 2004, Lehtinen 2004). Invertebrates, reptiles, or other

species of amphibians have been observed acting as predators, competitors, parasites, and

prey for the inhabitants of the phytotelm. In addition to these biotic factors, the small

bodies of water may be prone to desiccation, have very low levels of oxygen, or contain

unpredictable amounts of food (Caldwell and Araujo 2004, Lehtinen 2004). The

inhabitants of the phytotelms must also respond to a range in other abiotic conditions

including temperature, moisture, amount of detritus, and canopy cover (Lehtinen and

Carfagno 2011, Silva et al. 2011). Spatial isolation may affect both the general shape and

size of the plant, in turn affecting the quality of the phytotelm within. Spatial isolation

may also help determine the frog’s ability to locate and inhabit the plant (Silva et al.

2011). In addition, certain morphological characteristics of the plant have been shown to

affect the phytotelm’s ability to hold and retain water and thus influence the quality of the

habitat (Zotz and Thomas 1999, Silva et al. 2011, Lin and Kam 2008). An increased

water volume was also shown to positively influence the occupancy of both Guibemantis

bicalcaratus and Guibemantis punctatus phytotelm-breeding frogs living within the

water-filled axils of the Pandanus plants (Lehtinen and Carfagno 2011). In addition, a

larger plant size may provide larger phytotelms with the ability to hold a greater volume

of water. Therefore, water volume and plant size may also be important factors

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contributing to the overall quality of the microcosm. Several studies have also analyzed

the effect of water chemistry and other aquatic variables when predicting frog occupancy

of phytotelms (Caldwell and Araujo 2004, Silva et al. 2011). However, results from

these studies varied, especially with respect to levels of dissolved oxygen and pH of the

water within phytotelms. Furthermore, little is known about the effect of water

temperature in terms of the challenges it presents for the frogs.

Evidence supports the hypothesis that some species of phytotelm-breeding frogs

actively select a specific microcosm to occupy based on these biotic and abiotic cues

(Heying 2004, Resetarits 1996). For example, Phrynobatrachus guineensis is highly

mobile and individuals move between water-filled cavities frequently, suggesting that

they have the ability to actively select their habitat on some level (Sandberger et al.

2010). Xenohyla truncate has been observed moving through vegetation at night, as if

actively moving to a more suitable habitat (Silva and Britto-­‐Pereira 2006). Similarly,

larvae of both Mantidactylus bicalcaratus and Mantidactylus punctatus have been

observed climbing along leaf surfaces to move to different axils (Lehtinen 2004). Female

Scinax perpusillus have also been observed both dipping their legs or hind body and

diving into and swimming around the small pool as if “testing the water” before selecting

a mate and spawning (Alves-Silva and Silva 2009). Poison dart frogs distribute their

offspring individually between phytotelms they have actively chosen (Summers 1992,

Williams et al. 2007). In most Dendrobates species, this behavior is performed by the

male (Summers 1992). This behavior ensures that the cannibalistic tadpoles do not have

a chance to eat each other, therefore maximizing reproductive success. Habitat selection

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in phytotelm-breeding frogs seems to be based on a number of biotic and abiotic factors.

However, very little is known regarding the behavior and ecology of most tropical

phytotelm-breeding frogs.

Individuals from one such species, Flectonotus fitzgeraldi (Hemiphractidae), are

commonly known as marsupial frogs. The larvae develop partially in the female’s dorsal

marsupium before they are deposited into the phytotelmata created within the leaf axils of

Xanthosoma jacquinii (Araceae) (Duellman and Gray 1983, Kenny 1969, Murphy 1997

pg. 63-65, RML unpublished observations). Therefore, larvae are already

developmentally advanced and presumably better able to cope with the challenges the

phytotelm presents. This strategy also reduces the amount of time the tadpole has to

remain in the microcosm.

In an attempt to better understand the ecological niche of the phytotelm-breeding

frog F. fitzgeraldi, this study explores the biotic and abiotic conditions contributing to the

overall quality of its habitat. Specifically, this study sought to answer the following

question: To what environmental characteristics do marsupial frogs respond in order to

select habitats that promote optimal fitness? Because very little is known about the

natural history of F. fitzgeraldi, additional insight was noted in this study. Ultimately,

this information may be valuable for future conservation efforts.

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METHODS

Study area and study system

This study was conducted in the rainforest on the Caribbean island of Tobago

over the course of eight days. Several trials were run the first day to standardize the

measuring technique. These trials were not included in the final analysis. Data analyzed

in this study were collected from July 28 to August 3, 2012 between the hours of 9:00 am

and 6:00 pm. The collection period fell within the rainy season, with temperatures

ranging from 22.6°C-29.1°C and humidity ranging from 85%-100%. Because the air

temperature and humidity were recorded every time a plant was sampled, these ranges

represent conditions within the study sites over the course of the day. Two study sites

were established on the island (see Figure 1). One site was located within the Tobago

Forest Reserve about a 20-minute hike upstream from a bridge on the Roxborough

Parlatuvier Road (11°17.221 N, 60°35.676 W, elevation: 410 m) (see Figure A1). The

second site was located along a tributary of the Bloody Bay River about 30 m upstream

from the coordinates 11°17.967’ N, 60°37.085’ W at an elevation of 56 m (see Figure

A1). Although rarely the dominant species in the rainforest, the understory herb

Xanthosoma jacquinii (Araceae) does occur in relatively high numbers in patches along

streams in both locations.

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Figure 1. Data for this study were collected on the Caribbean island of Tobago. Tobago is a relatively small island (300 km2) located NE of Trinidad (4,768 km2). Together, the islands form the Republic of Trinidad and Tobago. The points indicate the two sites sampled in this study. The NW point corresponds to the Bloody Bay site and the SE point corresponds to the site in the Forest Reserve. Flectonotus fitzgeraldi was found at both locations. Flectonotus fitzgeraldi tadpoles and adults of both sexes inhabit the phytotelms

created within the leaf axils of X. jacquinii (RML unpublished data, personal

observations) (see Figure 2). Adult individuals have been observed inhabiting

phytotelms in the Xanthosoma plant at both these locations in years past (RML

unpublished data). Kenny (1969) also found F. fitzgeraldi tadpoles in the base of a

Xanthosoma plant. He noted that 26 tadpoles were found together in a single phytotelm

containing approximately 200 mL of water. This is the only historical sighting of F.

fitzgeraldi tadpoles. Adults have also been found in other terrestrial plants, including leaf

 

 

 

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axils of bromeliads and rolled-up leaves of Heliconia plants (Murphy 1997). The latter

do not retain water so these leaves may only be used for shelter, as reproduction is

limited to phytotelms (although the bracts of Heliconia flowers may serve as viable

phytotelms). Flectonotus fitzgeraldi is probably terrestrial by day and arboreal at night

based on observations made by Duellman and Gray (1983) for F. pygmaeus in

Venezuela. The frogs are crepuscular, and begin calling an hour before and continue

calling an hour after sunset (Murphy 1997, Kenny 1969). At dusk, the frogs were

observed leaping between branches of a bromeliad-laden tree, eventually entering the

bromeliads (Murphy 1997). Murphy notes that the leaps are long and fast, making the

frog’s capture difficult. He also observed adults crossing forest roads on rainy nights.

These observations collectively describe everything previously known about the habitat

of F. fitzgeraldi. On a larger scale, this species occurs on Trinidad, Tobago, and on the

Península de Paria in Venezuela (Murphy 1997).

Figure 2. The relative difference in male and female body shape was used to distinguish between the sexes in the field. This sex determination was based on the assumption that males had a more tapered body than females.

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Because amplexus and oviposition have not been observed in this species, the

following behaviors are inferred from observations made by Duellman and Maness

(1980) of F. pygmaeus. Immediately after eggs are fertilized, the male is thought to use

his hind limbs to individually push each egg up into the marsupium on the female’s

dorsum where they develop from small fertilized eggs into fairly well-developed

tadpoles. The clutch size for this species is the smallest in the species group, ranging

from 2-6 offspring (Murphy 1997, RML unpublished observations). The developing

embryos form distinct, round protrusions on the female’s dorsum (Murphy 1997,

personal observations). Duellman and Gray (1983) suspect females may be capable of

producing multiple broods per season, but more research is necessary to confirm this

hypothesis. When the tadpoles reach advanced stages of development (stages 39-41 of

Gosner 1960), they are deposited by the female into a phytotelm (Murphy 1997). Water

held within this phytotelm provides a pool just large enough to support the tadpoles as

they metamorphose into adults. Kenny (1969) observed that metamorphosis occurred

five days after leaving the parent. During this period, tadpoles are well supplied with

yolk and do not feed (Kenny 1969). While there are no published studies describing the

feeding behavior and diet for adult F. fitzgeraldi individuals, it may be inferred from

similar species that this frog is a dietary generalist. Therefore, the frog is expected to eat

any non-vegetative matter it can reasonably fit into its mouth.

Flectonotus fitzgeraldi has been observed to inhabit the phytotelms created within

the leaf axils of Xanthosoma jacquinii from the Araceae family (see Figure 3). This plant

has large leaves and thick, fleshy decumbent stems (Simmonds 1950). The plant

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produces flowers and seeds and also propagates vegetatively (see Figure 4). It produces

grey latex previously thought to be poisonous (Simmonds 1950). The entire plant gives

off a rotten stench (Simmonds 1950, personal observations).

Figure 3. The phytotelms are found at the leaf axils within Xanthosoma jacquinii. This image is drawn from a photo and provides insight into the structure of the plant. To establish a relative size scale, the backpack at the base of the plant is approximately 50 cm tall.

This  color  distinction  is  considered  the  “top  of  the  trunk.”    The  height  of  the  plant  is  measured  from  the  ground  to  this  point.    The  DBH  is  also  measured  at  this  point.  

 

-­‐21-­‐    

a) b) Figure 4. The trunk of Xanthosoma jacquinii. It may either emerge directly from the ground (a) or grow vegetatively (b). In both situations, roots extend from higher on the trunk down into the soil. The height of the plant was measured from the level of the soil.

Very little information is known about this plant, although one study noted it was

found in rocky ravines and along streams on the nearby island of Trinidad (Simmonds

1950). In Trinidad, it has been found throughout the wetter northern parts of the island

growing on metamorphic rock or sandstone. This species has been recorded at altitudes

up to 760 m on this island, although the highest point in Tobago is only 549 m

(Simmonds 1950, Murphy 1997). In Tobago, this plant seems to grow in relatively dense

clusters and seems to be limited to areas of undisturbed deep forest (personal

observations, RML unpublished data). Although Simmonds (1950) describes the plant to

be “locally abundant” in Trinidad, we found that locating these patches in Tobago was

relatively difficult and the ones we found always occurred in undisturbed forested areas.

However, the search strategies used to make this observation were limited to casual

observations while collecting data for this study and others conducted in years past.

Although extensive additional data is needed to support this conclusion, it seems likely

that the plant’s long-term survival is dependent on the preservation of old-growth forests.

-­‐22-­‐    

Plant selection

Five patches of Xanthosoma jacquinii were sampled at each site, each patch

containing ten individuals (see Figure A1). Patches were chosen haphazardly along a

stream. The first plant encountered when hiking up the stream was used as starting point.

From this origin, the nearest nine other individuals were selected based entirely on spatial

distribution. Therefore, the selected plants always occurred further upstream or further

up the bank of the stream in relation to the starting point. Together, these individuals

collectively formed a “patch.” In order to be included, a plant had to have a DBH

≥4.5cm, contain at least two leaf axils, and not exceed 190 cm in height. Preliminary

observations showed that plants smaller than these minimum criteria did not have

phytotelmata large enough to serve as viable microhabitats for F. fitzgeraldi. In addition,

plants exceeding 190 cm in height were not included because they were outside the

observer’s range of visibility. Individuals were not considered a part of the patch if they

were more than three meters away from another Xanthosoma jacquinii already

established to be part of the patch. The distance between any two plants in separate

patches always exceeded 3 meters, and often much more. Plants sampled within these

patches were measured for a number of characteristics (see ‘Habitat Characterization’

below).

In addition to the plants sampled within the established patches, about 10 hours

were spent informally searching plants which had not already been examined for F.

fitzgeraldi. Of this time, approximately 8 hours were spent in the Bloody Bay site and 2

hours were spent in the Forest Reserve site. This searching became crucial to increasing

-­‐23-­‐    

the sample size of occupied plants given the time constraints since relatively few

Xanthosoma in the established patches contained F. fitzgeraldi. During this informal

searching, every plant encountered was examined for frogs. The path taken to find these

plants was random on a small scale but systematically covered a very large area. The

route was dictated by plant densities, as more time was spent in areas more densely

populated with X. jacquinii. At Bloody Bay, a high density of plants often occurred

further up the bank of the stream in addition to the populations already surveyed near the

stream. Therefore, extensive time was spent examining plants high on the surrounding

slopes. At the Forest Reserve, efforts to mimic the sampling technique along the high

slopes were hindered due to topographical differences. Although the slopes along the

streams were not as high, the sampling effort still remained focused on surveying areas

with the largest X. jacquinii density. If F. fitzgeraldi was found during these informal

plant surveys, the occupied plant was measured identically to the formally sampled plants

and the resulting data were included in the final analysis.

Frog surveys

Each plant was surveyed for F. fitzgeraldi immediately upon approach. Leaf axils

were examined closely for any individuals. The surveying continued long enough to be

confident about the occupancy status (frogs present or frogs absent) and varied based on

the relative size of the plant (range: 30 s - 3 min) (see Figure 5). In addition to peering

directly into the top of a phytotelm, a headlamp was held against the base of the petiole to

illuminate the depths of the phytotelm through the petiole (see Figure 6). This technique

-­‐24-­‐    

helped distinguish frogs hiding deep in the base of the phytotelm from debris and other

organic matter. If any organic matter was questionable, an eyedropper was used to prod

the matter for movement. Because of the small size of the phytotelms and structurally

simple nature of the plant, it was easy to survey X. jacquinii plants thoroughly, and

adequate time ensured that few frogs (if any) were missed.

Figure 5. Xanthosoma jacquinii plants may have many leaves. The time required to sample each plant for frogs ranged from 30 s – 3 min. based on the number of leaf axils it contained. This figure shows how the petioles protrude from the main trunk. Although this figure shows flower buds emerging from the central trunk, the vast majority of plants did not have buds, flowers, or fruits at the time the study was conducted. The circled regions indicate the highest and lowest phytotelm. New leaves grow vertically from the top of the main trunk and “uncurl” as they mature. If the petiole was bent downward in a way that positioned the leaf lower than its axil, the phytotelm was destroyed because the water drained from the axil. Therefore, it was not counted in the analysis.

-­‐25-­‐    

Figure 6. A head lamp was held directly against the base of the phytotelm to illuminate its depths more clearly. The arrow indicates the direction of the light.

Habitat characterization

In order to determine the biotic and abiotic factors potentially influencing the

quality of the phytotelms F. fitzgeraldi inhabit, a variety of measurements were taken

(see Table 1).

-­‐26-­‐    

Table 1: The phytotelms were characterized by a number of biotic and abiotic factors. Data were collected based on the following variables. The shaded variables were eliminated from the final multiple logistic regression model because they were highly correlated with at least one other variable. The variables were considered highly correlated if they had a correlation coefficient >0.7 using the Spearman Test. Independent Variables Categorical or

continuous Explanation

Canopy cover Categorical (0-4 scale), 0=100% canopy cover, 4=0% canopy cover Detritus Categorical (0-4 scale), 0=leaf axils completely full of detritus, 4=leaf axils

devoid of detritus Invertebrate density Categorical (0-4 scale), 0=no invertebrates, 4=very high density of invertebrates. Invertebrate presence Categorical 0=no invertebrates, 1=invertebrates present Invertebrate size Categorical 0=no invertebrates, 1=only small invertebrates present (<7mm),

2=only large invertebrates present (>7mm), 3=both small (<7mm) and large (>7mm) invertebrates present

Volume of water Categorical (0-4 scale), 0=no water in phytotelm, 4=phytotelm completely full of water

Depth of water Continuous Measured from the base of the phytotelm to the surface of the water (to the nearest half-centimeter)

Oxygen concentration Continuous Measured by Oakton probe in mgO2/L water

Oxygen concentration Continuous Measured by Oakton probe in % O2 pH Continuous Measured by Oakton probe Temperature of water Continuous Measured by Oakton probe in °C Trunk height Continuous Measured from the ground to the point on the central trunk where a

color change occurs between the green leaf stalks and brown trunk (see Figure 3).

Height of lowest phytotelm

Continuous Measured from the ground to the point on the main stem where the lowest phytotelm protrudes (see Figure 5 and 8). (This is usually only a few centimeters higher than the “trunk height” measurement.)

Height of highest phytotelm

Continuous Measured from the ground to the point on the main stem where the highest phytotelm protrudes (see Figure 5 and 8).

Diameter at breast height (DBH)

Continuous Measured using a DBH tape around the top of the trunk indicated by a color change between the green leaf stalks and brown trunk (the same point on the trunk used to measure trunk height) (see Figure 3). This standard was used because not all the plants were breast height, but all had leaves protruding from a central trunk.

Length of petiole Continuous Measured from the base of the leaf to the connection point between the petiole and the trunk (see Figure 7 and 8). The longest petiole of the plant was measured.

Length of leaf Continuous Measured from the base of the leaf where the petiole connects to the tip of the leaf. The largest leaf on the plant was measured (see Figure 7).

Number of leaf axils Continuous A leaf axil was only counted if it had the ability to hold water (see Figure 5 and 10).

Number of leaves Continuous A leaf was counted if the tip protruded at least 30 cm from the top of the main stem (see Figure 5).

Nearest X. jacquinii neighbor

Continuous Distance from the trunk of the measured X. jacquinii to the trunk of the nearest X. jacquinii neighbor

Nearest neighbor (non-X. jacquinii)

Continuous Distance from the trunk of the measured X. jacquinii to any part of the nearest non-X. jacquinii neighbor

Distance to water Continuous Distance from the trunk of the measured X. jacquinii to the edge of the nearest stream bed

-­‐27-­‐    

Categorical variables included a qualitative estimate of forest canopy cover over

the plant, detritus levels in the leaf axils, invertebrate abundance, and the volume of water

contained within the phytotelm relative to its potential capacity. All of these categorical

variables were measured on a 0-4 scale. In addition, notes were taken on the relative

types of invertebrates and their sizes (larger or smaller than the 7 mm cutoff used by

Caldwell and Araujo (2004) to distinguish between potential competitors or food sources

for the adults). The depth of the water within the phytotelm was also recorded. This

measurement was taken from the base of the phytotelm to the surface of the water,

rounded to the nearest half-centimeter. If the plant was occupied, the specific phytotelm

the F. fitzgeraldi individual inhabited was measured. However, if the plant was

unoccupied, an average of the water level and detritus level in all of the phytotelms

collectively was estimated and recorded.

Water chemistry data was also recorded using a calibrated Oakton 300 series

Dissolved Oxygen/pH/Temperature Meter. Dissolved oxygen was measured in both

mg/L and percent. In addition, pH and water temperature were also recorded. An eye-

dropper was used to extract approximately 25-30 mL of water from the phytotelms and

this water was transferred to the rubber cap normally used to cover the probe of the

Meter. After the probe was inserted into this cap, readings were taken and recorded. If

the plants were occupied, only water from the inhabited phytotelm was measured. If the

plant was unoccupied, the eye-dropper was used to take samples from all of the

phytotelms and this water was all mixed together in the rubber cap before the probe was

inserted.

-­‐28-­‐    

Morphological measurements of the plant included trunk height, highest and

lowest phytotelm heights, longest petiole length, length of largest leaf, number of leaves

and number of leaf axils (see Figures 7 and 8). In addition, several other variables

including distance to the nearest X. jacquinii neighbor, distance to nearest neighboring

plant of any species other than X. jacquinii, and distance to the nearest stream were also

recorded to provide more insight into the surrounding habitat. Collectively, these data

were used to characterize the microhabitat for F. fitzgeraldi.

Figure 7. The length of the petiole and the length of the leaf were measured. For each plant, the longest petiole was measured. Likewise, the largest leaf was also measured. Typically these were correlated so that the longest petiole had the largest leaf.

Figure 8. Phytotelm formed at the base a leaf axil in X. jacquinii. The star indicates the reference point used in the following measurements: height of highest phytotelm, height of lowest phytotelm, and length of the petiole.

-­‐29-­‐    

Selecting variables for the multiple logistic regression model

The Spearman Test for correlation was used to identify any variables that had a

correlation coefficient over 0.7, the cutoff used for this model. Any variables more

highly correlated than 0.7 were no longer considered independent, and thus eliminated

from the model.

Invertebrate density, invertebrate presence or absence, and invertebrate size were

all highly correlated with each other. Ultimately, invertebrate size was chosen to remain

because it represents both an objective measure of invertebrate presence and contains

information indicating the relative size of the invertebrates. Therefore, this variable may

provide insight into the role of the invertebrates, acting as either predators (large

invertebrates >7 mm) or sources of food for the adult F. fitzgeraldi (small invertebrates

<7 mm) (Caldwell and Araujo 2004).

In addition, the relative volume of water in the phytotelm was highly correlated to

the depth of the water in the phytotelm. In theory, these variables represent very different

measurements. The “volume of water” measurement represents the amount of water

within the phytotelm relative to the phytotelms capacity to hold more water. For

example, a phytotelm that was half-filled to its capacity was recorded as a “2” on the 0-4

categorical scale, while a phytotelm filled to its brim with water was recorded as a “4”.

A dry phytotelm was recorded as a “0”, and a phytotelm with water taking up about 25%

or 75% of its total volume was recorded as either a “1” or “3”, respectively. In contrast,

the “depth of water” measurement was a continuous variable representing the actual

depth of the water in the phytotelm, measured from the base of the phytotelm to the

-­‐30-­‐    

surface of the water and estimated to the nearest half-centimeter. However, the “volume

of water” and “depth of water” variables were highly correlated. Ultimately, the “depth

of water” variable was chosen to remain because it represents a more precise, quantitative

estimate of the actual volume of water present in the phytotelms, considering they range

slightly in size.

The dissolved oxygen was recorded in both mg O2/L water and percent O2 within

the water. Because these variables were highly correlated, the variable representing the

measurement in mg O2/L water was chosen because it represents a more quantitative

measurement of the amount of oxygen present in the water.

The trunk height, height of the lowest phytotelm, and height of the highest

phytotelm were also highly correlated. Trunk height was used to represent all of these

variables.

In addition, the number of leaves and the number of leaf axils were highly

correlated. Because some leaves protruded vertically from the top of the plant, they did

not have an axil that could potentially fill with water. Therefore, the variable

representing the number of leaf axils was chosen to remain in the model for further

analysis because it better represents the actual number of potential phytotelms available

for F. fitzgeraldi to inhabit.

After eliminating seven highly correlated variables, fifteen independent variables

remained to be included in the multiple logistic regression model.

-­‐31-­‐    

Preliminary testing

When a multiple logistic regression model was used to analyze the effect of both

the categorical and continuous variables on the single dependent variable (presence or

absence of F. fitzgeraldi), multiple error messages occurred in the SPSS program.

Therefore, a multiple logistic regression model was used to separately analyze the effect

of only the categorical variables (canopy cover, invertebrate size, and detritus) on all 106

plants. This preliminary analysis did not provide any evidence supporting the

significance of these variables (canopy cover: p=0.466, invertebrate size: p=0.638,

detritus: p=0.934). Therefore, the categorical variables were removed from the data set

and the continuous variables were analyzed separately.

-­‐32-­‐    

RESULTS

The ecological niche of F. fitzgeraldi was defined and described using both

categorical and continuous variables. The baseline data provide insight into the range of

conditions the frog faced and the relative frequency that these conditions occurred in this

study (see Table 2 and 3). Although all variables measured during the data collection

period are included in these tables, not all of these variables were included in the final

analysis (see “Selecting Variables for the Multiple Logistic Regression Model” section).

Table 2. Descriptive statistics document the range of conditions that would be encountered by the frog if it were to occupy a phytotelm in the observed plant. Only the continuous variables are included in this table. Because the leaf axils in eight plants were dry, the aquatic variables could not be observed. Note the tight range and low standard deviation for these aquatic variables, in contrast to the relatively wide ranges observed for other variables. Variable n Range Average Standard

Deviation Depth of water 106 0-6 cm 1.7 cm 1.2 cm Oxygen concentration of water 98 90.4%-100% 97.5% 2.4% Oxygen concentration of water 98 7.22 - 8.54 mg O2/L 7.90 mg O2/L 0.29 mg O2/L Temperature of water 98 21.0-28.7°C 26.2°C 2.1°C pH of water 98 4.36-7.30 5.99 .69 Trunk height 106 1-190 cm 55 cm 39 cm Height of lowest phytotelm 106 1-193 cm 63 cm 40 cm Height of highest phytotelm 106 14-200 cm 78 cm 41 cm Diameter at breast height (DBH) 106 4.5-20 cm 7.9 cm 2.44 cm Length of petiole 106 54-197 cm 101 cm 23 cm Length of leaf 106 27-57 cm 41 cm 7 cm Number of leaf axils 106 2-14 6 2.5 Number of leaves 106 3-16 7 2.8 Nearest X. jacquinii neighbor 106 6-260 cm 70 cm 48 cm Nearest neighbor (representing any species other than X. jacquinii)

106 1-120 cm 34 cm 25 cm

Distance to water 106 0-20 m 4.9 m 4.1 m

-­‐33-­‐    

Table 3. Several categorical variables were also used to document the range of conditions that would be encountered by the frog if it were to occupy a phytotelm in the observed plant. Each categorical variable was recorded according to the described scale. For each variable, the number of plants that fit into each category was recorded. Variable n 0 1 2 3 4 Notes Canopy cover

106 52 51 2 0 1 (0-4 scale), 0=100% canopy cover, 4=0% canopy cover

Detritus 106 2 22 31 38 13 (0-4 scale), 0=leaf axils completely full of detritus, 4=leaf axils devoid of detritus

Invertebrate density

106 14 50 17 19 6 (0-4 scale), 0=no invertebrates, 4=very high density of invertebrates.

Invertebrate presence

106 14 92 0=no invertebrates, 1=invertebrates present

Invertebrate size

106 14 54 28 10 0=no invertebrates, 1=only small invertebrates present (<7mm), 2=only large invertebrates present (>7mm), 3=both small (<7mm) and large (>7mm) invertebrates present

Volume of water

106 8 49 32 14 3 (0-4 scale), 0=no water in phytotelm, 4=phytotelm completely full of water

Between both sites, 106 plants were sampled for F. fitzgeraldi. Of these plants,

11 contained frogs (see Table A1). Because the leaf axils in eight of the plants were dry,

water chemistry data could not be taken. After running the multiple logistic regression

model on the categorical variables using all 106 plants, the eight dry plants were removed

from the model to complete further analysis.

A multiple logistic regression model was run using the remaining continuous

variables on the 98 plants containing water in at least one leaf axil (see Table 4). Both

the Omnibus Test of Model Coefficients (p<0.001) and the Hosmer and Lemeshow Test

(p=0.837) indicate that this model was a significant predictor of the presence or absence

of F. fitzgeraldi in X. jacquinii plants.

-­‐34-­‐    

Table 4: This multiple logistic regression model analyzed whether the continuous variables were significant predictors of the frog’s presence or absence. This model found that water depth was the only significant predictor of the frog’s occupancy status. The B value represents the coefficient calculated by the model for each variable (positive coefficients indicate that the likelihood of occupancy increases as the continuous variable increases in value, negative coefficients indicate that the likelihood of occupancy decreases as the continuous variable increases in value). The Wald values provide insight into the significance of the variable in the model. The p-values indicate the statistical significance of each variable. The Odds ratio indicates how the odds of finding a frog changes as the continuous variable increases by one unit. If the Odds ratio is >1, frogs are more likely to be found as the continuous variable increases. If the Odds ratio is <1, the chances of finding a frog decreases as the continuous variable increases. See Table 1 for definitions of variables. Independent variable

B Wald P-value

Odds ratio

Water depth 2.761 5.185 .023* 15.819 Height .005 .120 .729 1.005 Length of petiole .072 3.182 .074 1.075 Length of leaf -.111 .461 .497 .895 Number of axils .315 .823 .364 1.371 DBH -.880 2.449 .118 .415 Neighbor (X. jac.) .015 .536 .464 1.015 Neighbor (other) -.020 .492 .483 .980 Distance to water .002 1.615 .204 1.002 Dissolved O2 (mg/L) 11.970 1.919 .166 158003.132 Water temperature .338 .181 .670 1.402 pH of water .125 .019 .890 1.133

-­‐35-­‐    

Water depth (p=0.023) was the only significant predictor of habitat occupancy (see

Figure 9a). Plants with phytotelms containing a greater volume of water were more likely

to be inhabited by F. fitzgeraldi than plants with phytotelms containing a lesser volume of

water, as measured by the depth of the phytotelm. The length of the plant’s longest petiole

was marginally significant (p=0.074) (see Figure 9b). As the length of the petiole

increased, the odds of finding F. fitzgeraldi in the plant also increased. DBH was the third

highest predictor of the presence or absence of frogs (p=0.118) (see Figure 9c).

Flectonotus fitzgeraldi were more likely to be found in plants with a smaller DBH.

Although dissolved oxygen (measured in mg O2/L) is the fourth highest predictor of frog

occupancy in this model, this variable was not significant (p=0.166) (see Figure 9d). If this

trend was more significant, it would suggest that a higher level of oxygen in the water is

beneficial for the frogs. None of the remaining continuous variables were significant.

-­‐36-­‐    

Figure 9: Each graph represents one of the following variables: (a) water depth (p=0.023), (b) length of petiole (p=0.074), (c) DBH (p=0.118), and (d) dissolved oxygen (p=0.166). For these variables, the mean values were calculated for both occupied and unoccupied plants. Each graph compares these calculated means. Error bars represent a 95% confidence interval. For water depth (Figure 9a), the average unoccupied plant had a depth of 1.5 cm (n=95) while the average occupied plant had a depth of 3.0 cm (n=11). If the plant was occupied, only the phytotelm found to be inhabited was measured. If the plant was unoccupied, all of the phytotelms in a plant were examined and a collective estimate was made to represent the average depth of the phytotelm in the sampled plant. In Figure 9b, the average length of petioles in unoccupied plants was 98 cm (n=95) while the average length of petioles in occupied plants was 127 cm (n=11). In Figure 9c, the average DBH in unoccupied plants was 8.4 cm (n=95) while the average DBH in occupied plants was 8.6 cm (n=11). In Figure 9d, the average dissolved oxygen concentration in unoccupied plants was 7.87 mg O2/L (n=87) while the average dissolved oxygen concentration in occupied plants was 8.12 mg O2/L (n=11). If a plant was unoccupied, water from multiple phytotelms within the same plant was collected and mixed before the sample was measured.

a) Water Depth (cm) b) Length of Petiole (cm)

c) Diameter at Breast Height (DBH) (cm) d) Dissolved Oxygen (mg O2/L)

 

-­‐37-­‐    

DISCUSSION

Habitat choice by Flectonotus fitzgeraldi was primarily driven by the availability

of water. It makes sense that the depth of water in the phytotelm was an important factor

influencing the choice of the frog because this water is essential for the development of

the tadpole (Kenny 1969). If tadpoles are deposited into a phytotelm with very little

water, the probability of desiccation is higher (Caldwell and Araujo 2004, Denver 1998,

Rudolf and Rodel 2007). Because tadpole survival is directly dependent on a constant

water supply, habitats that provide a greater assurance that desiccation will not occur are

favored (Caldwell and Araujo 2004). Thus, the ability of the frog to detect this larger

water volume when depositing its offspring should increase the individual’s overall

fitness. Data from this study suggest that water availability serves as the best indicator of

habitat quality, as water depth was the only significant predictor of the occupancy of the

frogs (p=0.023).

In addition to assuring an appropriate habitat for tadpoles to develop, phytotelms

with comparatively more water also seem to provide a microhabitat favored by adults. In

fact, ten of the eleven occupied plants contained adults. Although very little is known

about the natural history or physiological requirements of F. fitzgeraldi, this occupancy

pattern seems to suggest that water-filled leaf axils are also beneficial for adults to

inhabit. This observation is consistent with previous studies which have shown that an

increased water volume positively influences the likelihood of occupancy for other adult

phytotelm-dwelling frogs (Lehtinen and Carfagno 2011, Silva et al. 2011). For example,

Lehtinen and Carfagno (2011) found that the volume of water in the leaf axils of

-­‐38-­‐    

Pandanus plants was one of the best predictors of habitat occupancy for both

Guibemantis bicalcaratus and G. punctatus of Madagascar. In addition, Silvia et al.

(2011) concluded that bromeliad occupancy is an adaptation to water scarcity for adults

of several frog species in Brazil. Data from my study suggests that adult F. fitzgeraldi

also tend to inhabit phytotelms with larger volumes of water. It seems advantageous for

mature females to select phytotelms with more water to inhabit, as tadpole survival

depends on water availability (Kenny 1969). Males may also use water volume as a cue

to select quality habitats in an effort to attract females. If females are attracted to the

quality habitats males are calling from, it may improve the overall fitness for both

individuals. This could simultaneously provide the male with the opportunity to mate

and allow the female to occupy a quality habitat, thus improving the chances of survival

for her future offspring.

In this study, three of eleven plants found to be occupied by F. fitzgeraldi

contained multiple individuals. In every case, all of the individuals occupied the same

leaf axil. Although very little is known about amplexus or other mating behaviors of F.

fitzgeraldi, it seems likely that these behaviors occur within phytotelms. In fact, all of the

phytotelms occupied by multiple adult individuals contained at least one male and one

female. A larger volume of water may provide a larger physical space for these activities

to occur. Therefore, an increased water depth may improve the quality of the

microhabitat for mating purposes and thus serve as an important cue for the frog to

detect.

-­‐39-­‐    

An increased water depth may also provide more protection against certain

environmental conditions, biotic intrusions, or other detrimental outside factors. In

addition to decreasing the chance of desiccation, a larger volume of water may better

resist rapid temperature changes due to fluctuating environmental temperatures (Lin and

Kam 2008, Paradise 2004, Sota et al. 1994). Although the overall environmental

conditions are not likely to vary too drastically in Tobago, the increased water depth may

still reduce the variation the frogs experience, even if only on a small scale. Personal

observation showed frogs were often found wedged tightly between the petiole and the

trunk at the very base of the phytotelm. In fact, many frogs wedged themselves even

deeper upon discovery. These frogs seemed to be seeking maximum protection from the

sudden intrusion. Therefore, a larger volume of water may increase the quality of the

frog’s microhabitat by increasing the spatial barrier between the frog and its environment.

Past research has shown that canopy cover and detritus levels may be correlated

with water volumes. For example, less canopy cover may increase the chances of

capturing new rain while simultaneously decreasing the chances that detritus will fall into

the phytotelm (Lehtinen 2004, Silva et al. 2011, Lehtinen and Carfagno 2011, Lin and

Kam 2008). New rain is beneficial as it helps increase the dissolved oxygen levels

(Caldwell and Araujo 2004). One study found that bromeliads located in the sun had

430% higher dissolved oxygen levels than bromeliads located in the shade (Silva et al.

2011). Silva et al. (2011) suggested that this variation was in part because the bromeliads

in the sun were able to collect fresh, oxygenated rainwater. Studies have found that an

increased level of detritus decreases the level of dissolved oxygen because microbes

-­‐40-­‐    

depend on this oxygen supply to decompose organic matter (Lehtinen 2004, Diaz and

Rosenberg 2008). Considering neither adult F. fitzgeraldi frogs nor tadpoles consume

organic matter, high levels of detritus are presumably not a beneficial characteristic for

the frog (Kenny 1969). The amount of detritus contained in a plant has been shown to

be negatively correlated with a plant’s water-holding capacity (Lehtinen and Carfagno

2011). Lehtinen and Carfagno (2011) suggest that G. punctatus probably uses detritus

load as a cue for water holding capacity, as plants under a relatively dense canopy collect

more detritus and receive less rainfall than plants under a more open canopy (Lehtinen

2004). Therefore, an increased volume of water in the phytotelm may be a direct result

of several other cumulatively important environmental conditions including decreased

canopy cover and decreased levels of detritus. Although these studies suggest both

canopy cover and detritus may be important factors to consider when predicting the

quality of the microhabitat, my study did not support this hypothesis. Neither canopy

cover (p=0.466) nor detritus (p=0.934) were individually significant in predicting the

occupancy of F. fitzgeraldi in X. jacquinii.

Although water availability was the primary driving force for habitat selection in

F. fitzgeraldi, petiole length was also a marginally significant variable (p=0.074).

Although not significant by the 0.05 standard assumed by this study, other pilot studies

have used a 0.1 critical point to figure out where to focus their attention to maximize the

chances of finding significant data in future follow-up research. Flectonotus fitzgeraldi

seemed more likely to occupy Xanthosoma jacquinii with longer petioles, but it is not

likely that they perceived this cue and responded to it directly. Instead, the petiole length

-­‐41-­‐    

may be correlated with the relative age of the leaf, which may in turn affect the quality of

the phytotelm (see Figure 10). Personal observations showed that younger leaves

emerging from the top of the plant had shorter petioles, as they were still growing.

Because these younger leaves often pointed directly upward, the size of the leaf axil was

compromised and thus the phytotelm’s potential to hold water decreased dramatically. In

addition, older leaves located lowest on the trunk also seemed to have shorter petioles

and likely smaller phytotelms as a result, because they emerged when the plant was

smaller. Personal observations showed that phytotelms resulting from older leaves often

appeared stretched out because as the trunk grew wider with age, the depth of the

phytotelm decreased (see Figure 10a). As a result, the phytotelm was not able to hold as

much water. Furthermore, the older leaves often bent downwards with age, ultimately

draining the phytotelm and destroying the microcosm (see Figure 10c). Therefore,

middle-aged leaves with longer petiole lengths seem to be correlated with larger, more

stable phytotelms. However, it is important to note that data measuring multiple petioles

on the same plant were not taken. Therefore, this suggested explanation is only based on

informal observations of the plant and future studies are needed to support the logic of

this argument.

-­‐42-­‐    

A) B) C) Figure 10. Phytotelms created by leaf axils. A) Represents a phytotelm created by a relatively new, young leaf. The petiole is generally thinner, oriented more vertically, and contains a relatively small, though often fairly deep phytotelm. B) Represents a “middle-aged” leaf. Petioles are typically longer and a bit wider at the base than younger leaves. Petioles are also not oriented as vertically as newer petioles, widening the phytotelm. Although this may create an overall larger phytotelm, the more vertical younger leaves may still create a deeper, though smaller phytotelm. C) Represents the leaf axil created by an aging leaf. With age, the petiole bends downward, eventually inhibiting the leaf axil’s ability to hold water. At this point, it is no longer considered a phytotelm, and thus not considered in the analysis.

Alternatively, it is possible that longer petioles are associated with larger

phytotelms. Although this idea cannot be directly supported from my study (considering

the examined leaf axils were never directly measured for size), longer petioles may be

necessarily wider at the base to structurally hold the weight of the leaf (see Figure 7). If

this is the case, the resulting phytotelm will also be larger. Because larger phytotelms

can hold more water, and water depth was found to be the only significant predictor of

frog occupancy, it is possible that longer petioles are associated with higher quality

phytotelms.

Furthermore, the overall shape of the plant is largely dependent on the length of

the petioles, as longer petioles allow the leaves to reach higher and extend farther

horizontally (see Figure 3). Therefore, petiole length may also be associated with overall

plant size, although height and DBH may also be used to represent the size of the plant.

-­‐43-­‐    

A large plant may be easier to locate in the ecosystem because its leaves extend farther

and it may be possible that as the frog moves between plants in the population, long

petioles increase the frog’s likelihood of encountering the plant.

While not significant, it is worth noting that the third highest explanatory variable

in the analysis was diameter at breast height (DBH) (p=0.118). Although minimal, this

variable still has some predictor value and our analysis suggests that frogs may slightly

favor plants with smaller diameters. If smaller diameters are associated with smaller

phytotelms, it may be possible that microhabitats resulting from plants with smaller

diameters are large enough for frogs but too small for larger predators or competitors

including snakes, crabs, or other large organisms. Therefore, plants with smaller

diameters may be beneficial to the frog and thus increase the quality of the plant.

However, the hypothesis that smaller phytotelms are beneficial to the frog directly

contradicts the previously described idea that larger phytotelms are more favored. In

fact, it may be possible that neither DBH nor petiole length is actually directly correlated

to phytotelm size. It may be possible for plants to have both large petioles and small

diameters, as these characteristics are not necessarily mutually exclusive. Furthermore,

the petiole length might be primarily an indicator of phytotelm quality based on the

relative age of the leaf, while DBH might provide more insight into the actual dimensions

of the leaf axil. However, data recording the physical size of the phytotelm was not taken

in this study. Therefore, claims suggesting either petiole length or DBH are correlated

with phytotelm size are not adequately supported by data and only speculative in nature.

Petiole length and DBH were positively correlated with each other based on the

-­‐44-­‐    

Spearman test (correlation coefficient=0.647, p<0.001). Although this suggests that as

petiole length increases, DBH also increases, the Spearman correlation coefficient did not

exceed 0.7, our cutoff for the multiple logistic regression model. Therefore, the variables

were treated independently. When examined individually, the DBH was a greater

predictor of frog occupancy (odds ratio: 0.415) than petiole length (odds ratio: 1.075)

(see Table 4). Ultimately, it is important to remember that neither trend was actually

significant.

The amount of dissolved oxygen in the phytotelm does not significantly predict

frog occupancy in this study (p=0.166). Because frogs have highly permeable skin

essential for cutaneous respiration, it seems possible that dissolved oxygen levels could

affect their physiology (Caldwell and Araujo 2004). Although the relatively large surface

area to volume ratio of water in the phytotelm likely decreases the time needed for the

dissolved oxygen to equilibrate with the environment, dissolved oxygen levels may still

vary greatly. One study found that dissolved oxygen levels varied by 430% within

tropical phytotelmata located in bromeliads in Brazil (Guimaraes-Souza et al. 2006). The

same study suggested that frogs assess the quality of their environment primarily through

cues from water chemistry. In fact, past research has observed frogs presumably

assessing the water chemistry of a small pool of water before selecting a quality habitat

and accompanying mate with which to spawn (Alves-Silva and Silva 2009, Downie et al.

2001). Caldwell and Araujo (2004) hypothesized that oxygen depletion was the reason

for mortality for several Allobates femoralis tadpoles living in phytotelms created by fruit

shells of Bertholletia excelsa, the Brazil nut tree. This study also found that Bufo

-­‐45-­‐    

castaneoticus were revived after a heavy rainfall, and thus their lethargic behavior and

fact that they floated upside down on the water’s surface before the rain could be

attributed to oxygen depletion. These observations suggest that higher levels of dissolved

oxygen in the water of the phytotelms would increase the quality of the microhabitat.

However, data from several other studies have found that water chemistry does not

significantly affect the quality of the phytotelm (Lehtinen 2004, Caldwell and Araujo

2004). Data from our analysis regarding F. fitzgeraldi supports the latter conclusion.

Previous studies have focused on the effect of rainfall on both dissolved oxygen

and amount of detritus in the phytotelms. This research has shown that phytotelmata

containing only rainwater consistently have higher concentrations of dissolved oxygen

than phytotelmata containing mostly detritus (Caldwell and Araujo 2004). These

variables are often related to each other because new rainwater may flush a phytotelm of

some of its accumulated detritus. In addition, an increased detritus often increases the

amount of microbial activity, in turn lowering the concentration of dissolved oxygen

(Lehtinen 2004, Caldwell and Araujo 2004, Ryan and Barry 2011). However, my study

found that dissolved oxygen concentration is not significantly correlated to detritus level

(correlation coefficient: -0.055, p=0.591). Furthermore, dissolved oxygen was also not

correlated with water depth (correlation coefficient: 0.132, p=0.196), contrary to the idea

that rainfall would increase both dissolved oxygen level and water depth simultaneously.

Despite the perceived challenges of dealing with a low dissolved oxygen concentration,

one study found that two phytotelm-breeding frogs in Madagascar, Mantidactylus

bicalcaratus and M. punctatus, actually have higher growth rates in the low oxygen

-­‐46-­‐    

levels (Lehtinen 2004). This is likely due to the fact that detritus served as a food source

for the tadpoles of these species and this food source was more beneficial than the

decreased levels of dissolved oxygen were harmful (Lehtinen 2004). Because F.

fitzgeraldi tadpoles are supplied with a large yolk and do not feed (Kenny 1969), high

levels of detritus were not expected to significantly increase the quality of the phytotelm.

Furthermore, once tadpoles reach a certain stage of development, they possess functional

lungs and can gulp air directly at the surface even if there is no oxygen in the water at all

(Lehtinen 2004). Although a decreased level of dissolved oxygen may decrease the

quality of the habitat for some species of frogs, data from our study concluded that

dissolved oxygen levels were not significant predictors of F. fitzgeraldi occupancy in

phytotelms created by X. jacquinii.

In addition to dissolved oxygen, my study concluded that neither pH nor water

temperature had any notable effect in our model of frog occupancy. Previous studies

have suggested contrasting views on the importance of pH and water temperature in

microcosm selection. A decreased pH increased the mortality rate and delayed

metamorphosis for Rana temporaria (Cummins 1986). Elevated water temperature was

also found to be a significant aquatic factor, accelerating the development of several

species of tadpoles in Virginia, including Rana temporaria (Smith-Gill and Berven 1979,

Laurila and Kujasalo 1999). Although both these studies and additional research state

that cues from the aquatic variables may be important factors contributing to the fitness

of the frog and thus quality of the phytotelm (Guimaraes-Souza et al. 2006, Silva et al.

-­‐47-­‐    

2011), these variables were not shown to be significant in other research (Caldwell and

Araujo 2004, Lehtinen 2004). My study supports the latter conclusion.

However, it is worth noting that the aquatic variables in this study had a relatively

small overall range (see Table 2). Therefore, the observation that frogs did not seem to

distinguish between certain aquatic variables may simply be due to the fact that very little

variation existed in the water temperature and chemistry of the measured phytotelms.

Flectonotus fitzgeraldi in this study seemed to have no choice but to inhabit a relatively

narrow niche when considering aquatic data alone. Therefore, this study found that

aquatic variables are not a valuable dimension on which to describe the ecological niche

of this phytotelm-dwelling species. However, further research may show a greater

variation in the properties of water in phytotelms located in different plant species or over

a larger geographic range in Tobago. Until this variation is found, the ability of F.

fitzgeraldi to tolerate a wide range within the aquatic variables remains unknown.

Invertebrates were recorded for presence, abundance, and relative size. A variety

of ants, crickets, spiders, millipedes, snails, earwigs, and scorpions were found in the

observed plants. Crabs and (although not invertebrates) two snakes (both Imantodes

cenchoa) were also found during informal surveys of X. jacquinii during the collection

period in 2012. My study found that the presence of these invertebrates did not

significantly predict the occupancy of the frog. This contradicts previous research

suggesting that invertebrates may decrease the overall quality of the habitat by acting as

either predators or competitors to the frogs. Caldwell and Araujo (2004) showed that

when potential insect predators were small (<7mm), they were eaten by Dendrobates

-­‐48-­‐    

tadpoles. Although F. fitzgeraldi tadpoles are non-feeding, it may be assumed that the

adults also eat small invertebrates based on observations of related frog species (Elinson

1990). However, if Dendrobates tadpoles were deposited in a water pool with a larger

predaceous invertebrate or larvae already present, the Dendrobates tadpoles were usually

eaten first (Caldwell 1993 and Caldwell and Araujo 2004). This is probably true for F.

fitzgeraldi tadpoles as well. In addition, the invertebrates may act as competitors for the

same resources the phytotelms provide (Caldwell and Araujo 2004, Murphy 2003,

Williams et al. 2007). Despite this research, my data do not show any significant

relationship between invertebrate presence and frog occupancy. Furthermore, neither

invertebrate presence nor size is correlated to any other factors in the analysis.

Other studies suggest that competition between different species of phytotelm-

breeding frogs may be a significant factor to consider when defining the niche of a single

species (Lehtinen and Carfagno 2011). However, as far as we know, F. fitzgeraldi is the

only obligate phytotelm-occupying frog species in Tobago. This study did not consider

the interactions between different species of amphibians, as no other species were found.

It is possible, however, that at least one species of snake (Imantodes cenchoa) is a

predator of F. fitzgeraldi. This hypothesis is based on the fact that two of these snakes

were observed occupying X. jacquinii phytotelms during informal surveys of the sites.

Past research suggests that there may be some relationship between the quality of

the phytotelm and either plant size or overall shape. Although two morphological

variables (petiole length and DBH) were already discussed, the baseline data collected for

this study collectively give a more holistic image of X. jacquinii. Even though Silva et

-­‐49-­‐    

al. (2011) did not examine X. jacquinii specifically, the authors state that a plant’s large

size may be caused by a number of factors that positively influence its growth including

decreased canopy cover, decreased detritus, and increased rainfall (Silva et al. 2011).

Furthermore, sun exposure has been shown to support larger, hardier plants, providing a

larger, more stable phytotelm for the frog to inhabit in both bromeliads in Brazil (Silva et

al. 2011) and bamboo stumps in Taiwan (Lin and Kam 2008). For G. bicalcaratus in

Madagascar, occupation rate increased with increasing plant width. In contrast, the same

study found that G. punctatus were more commonly found in tall plants (Lehtinen and

Carfagno 2011). Some studies have observed the general shape of a plant to be an

important abiotic factor in determining the quality of the plant because shape affects both

the amount of water a leaf axil can hold (Zotz and Thomas 1999) and the quality and

stability of each microhabitat created (Silva et al. 2011). Although there are different

ways to define and describe a plant’s “shape”, Zotz and Thomas (1999) based their

definition for bromeliad shape on three factors: tank capacity, catchment area for

precipitation, and aspects of tank geometry that affect evaporation. Silva et al. (2011)

observed that bromeliad shape was often determined by its position within a larger

population. Individuals located on the edge of a cluster were generally bulkier and

shorter, with lighter green leaves, stronger thorns, more access to sunlight, and less

accumulation of detritus. These bromeliads were observed to be more desirable to frogs

because the general shape allowed for a larger volume of water to be collected between

the leaves, likely reducing desiccation rates. However, these studies of bromeliads

provided little insight into how the morphological measurements of X. jacquinii might

-­‐50-­‐    

affect the quality of the resulting phytotelms simply due to the structural differences

between the plant species.

Because this is the first study to analyze the relationship between the

morphological measurements of X. jacquinii and the resulting characteristics of its

phytotelms, extensive baseline data were taken (see Table 1). However, only

independent variables were used in the Multiple Logistic Regression model. Therefore,

some of these original variables were excluded (see “Selecting Variables for the Multiple

Logistic Regression Model” in Methods section Table 1). Although two of the top three

predictors of F. fitzgeraldi occupancy (including petiole length and DBH) were

morphological characteristics of the plant, no other notable relationships or correlations

were found between any of the other morphological measurements in relation to frog

occupancy.

Although data quantifying several aspects of the plant’s spatial location were

taken, these variables were also not significant predictors of frog occupancy.

Specifically, the distance was measured from the X. jacquinii containing the observed

phytotelm to the nearest other X. jacquinii and nearest plant of any species (other than X.

jacquinii). This was designed to provide insight into the relative density of the X.

jacquinii population in relation to the density of surrounding plant species. However, the

total area the patch covered was not measured, therefore exact densities cannot be

calculated. Personal observations showed that more densely populated X. jacquinii

populations tended to have fewer plants representing different species distributed

amongst the X. jacquinii individuals. Furthermore, X. jacquinii populations that were

-­‐51-­‐    

spread over a wider geographic area tended to have more plants of other species

distributed throughout the range of the observed X. jacquinii patches. Although this trend

seems to be characteristic to the populations of X. jacquinii in this study, neither these

informal observations nor the statistical model suggest these factors are significant when

predicting frog occupancy. In addition, the distance from the measured X. jacquinii to

the nearest stream was also recorded, although this variable was not a significant

predictor of the frog’s occupancy status. This makes sense, as F. fitzgeraldi does not live

directly in the stream during any part of its life cycle, instead relying solely on the

phytotelms for breeding and seeking shelter (Murphy 1997).

Several studies have attempted to explore the relationship between environmental

variables, plant morphology, and the local distribution of frogs (Xavier and Napoli 2011,

Lehtinen and Carfagno 2011, Silva et al. 2011). These studies are based on the

assumption that environmental variables affect plant morphology which in turn affect the

characteristics of the phytotelms. In addition, the studies assume that the frogs will

occupy the phytotelm that maximizes their evolutionary fitness. Similar to the present

study, Silva et al. (2011) sought to explore which biotic or abiotic conditions ultimately

influence the quality of this microhabitat. Morphological characteristics of the plant,

water chemistry, and spatial information were all considered. Silva et al. (2011)

concluded that frogs were more likely to be found under certain conditions that could be

characterized by morphological traits. For example, bromeliads located around the edges

of clusters of multiple plants were shown to be particularly well-inhabited. The authors

rationalized that the overall shape of the edge plants allowed for larger phytotelms in

-­‐52-­‐    

contrast to the relatively crowded bromeliads located in the middle of the patch.

Therefore, occupancy patterns observed on the small scale may be used to provide insight

into occupancy or distribution patterns on a larger scale.

Although it seems safe to assume that factors affecting X. jacquinii distribution

will affect F. fitzgeraldi distribution on some level, the frog distribution cannot be

directly predicted from the distribution of the plants they inhabit (Silva et al. 2011,

Xavier and Napoli 2011). Even though a better understanding of the plant distribution

may provide some insight into the frog geographic distribution, the ranges of both the

plant and the frog species are unlikely to be perfectly correlated. Therefore, extensive

additional data relating to occupancy patterns for F. fitzgeraldi on both the small and

large scale are needed before any real distributional predictions can be made.

My study found that F. fitzgeraldi has a relatively broad ecological niche (see

Table 2 and 3). Because the frogs were found to inhabit phytotelms characterized by a

wide variety of environmental and biotic conditions, it seems safe to conclude that the

species has the ability to withstand a large range of ecological conditions. In fact, my

data showed that water depth was the only significant variable predicting the occupancy

of frogs. Therefore, although habitat selection does seem to occur on some level, the

broad ecological niche of F. fitzgeraldi allows the frog to occupy a wide variety of

phytotelms. As long as the phytotelm provides an adequate water supply, my study

suggests that F. fitzgeraldi is rather flexible in its choice of phytotelm. Therefore, it

might be possible for F. fitzgeraldi to occupy other types of phytotelms including

treeholes, bamboo stumps, bromeliads, or phytotelms created by other plants if human

-­‐53-­‐    

disturbances threaten X. jacquinii. From a conservation perspective, this provides hope

for the frog’s long term survival despite possible changes to surrounding environmental

or ecological conditions.

-­‐54-­‐    

ACKNOWLEDGEMENTS

I gratefully acknowledge the support and guidance I’ve received from a large

number of people throughout the course of this project. First, I’d like to thank Dr.

Lehtinen. To say he’s been a very special mentor over the past three years would be an

incredible understatement. The important lessons I’ve learned and memories I have of

our time together will stay with me for many years to come. I would also like to thank

Dr. Loveless for teaching me more than I imagined I’d learn throughout the whole editing

process. I truly believe her new perspective and helpful insight has proven invaluable in

many significant ways, and I thank her for all of her patience. I am also very thankful for

Dr. Fraga’s insight, and for his wise listening ear. Of course, I am greatly indebted to the

College of Wooster Biology Department for providing me with this amazing opportunity

in the first place, and for the maintinence and use of field equipment. In addition, the

Copeland Fund provided monetary support, making my adventure to Trinidad and

Tobago possible. Finally, I would like to thank my friends and family for their endless

and enthusiastic encouragement throughout the entire project. I will always be grateful

for their support and patience as I truly immersed myself into the “world of IS.” Of

course, the carrel gifts and awesome visits always made me smile, too. I also owe a

special thank you to Matthew Germaine, for both the creation of the most epic carrel-fort

to have ever existed, and for providing me with my very own IS soundtrack. I can

honestly say I now know every song by heart.

-­‐55-­‐    

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APPENDIX

a) b) Figure A1. This study was conducted between two sites at both a tributary of the Bloody Bay River (a) and the Tobago Forest Reserve (b). Maps are replicated from simple sketches in field notes. The green ovals represent a sampled patch of X. jacquinii. The numbers labeling each patch correspond to the order in which the patches were sampled, and thus the label of the patch itself. The numbered red dots indicate plants found to be occupied that were not included in a patch. The light green dots indicate relatively high densities of X. jacquinii. Because the maps are not drawn to scale, they provide no more than a rough idea of where the patches are located in relation to each other and to other major landmarks.

=  Numbered  patch  of    X.  jacquinii  =  Individual  occupied    X.  jacquinii  not  included    in  a  patch  =  Many  X.  jacquinii  located  here  

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Table A1: Summary of my field observations for each occupied X. jacquinii. The following notes provide additional insight into the frog’s behavior. Although the model analyzing the significance of the categorical variables was based on an average of all of the leaf axils, informal additional notes were taken describing the characteristics for each inhabited phytotelm. Plant ID Information

F. fitzgeraldi

Notes on frog behavior Extra notes about the individual occupied phytotelm or overall plant

BB3-30 7/30/12 3:20 pm Bloody Bay

2 tadpoles Both still upon first observation. The first was found when it was caught at the tip of the eyedropper being used to collect a water sample. The second was found at the base of the same phytotelm.

Phytotelm: Water depth: 2cm (50% filled), no detritus, no invertebrates, clean fresh-looking middle-aged leaf located 88 cm high (approximately halfway between newest and oldest leaves) Plant: Nothing noteworthy

BBfrog1 7/31/12 4:00 pm Bloody Bay

1 adult Jumped out in a projectile motion toward my face immediately as I pulled the leaf back for inspection. The soft, wet, squishy underside stuck to my hand (which reached up to block my face). Unfortunately, I instinctively shook it off before I realized it was a frog. After a thorough search of the forest floor, it could not be found.

Phytotelm: water depth: 2cm (25% filled), clean fresh-looking leaf axil supporting a full-grown leaf located slightly closer to the newer leaves, small spiders and one large ant crawling between the leaf axils Plant: Growing vegetatively (see Figure 6), located on steep slope

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BBfrog2 7/31/12 4:30 pm Bloody Bay

1 adult Found wedged deep in the phytotelm, jumped out immediately as leaf was angled back to take a picture.

Phytotelm: Water depth: 3cm (50% filled), no detritus, no invertebrates, clean fresh-looking middle-aged leaf located approximately halfway between newest and oldest leaves Plant: Little fungal vine on outside of trunk

BBfrog3 7/31/12 4:45 pm Bloody Bay

1 adult female carrying 5 fairly developed eggs on her back

When I first saw her, she was sitting just above the water line. As I pulled back the leaf, she sought shelter in the water, wedging herself deeply at the base of the phytotelm. Upon further disturbance (angling leaf for better camera view), she jumped away.

Phytotelm: Water depth: 4cm (50% filled), no detritus although small amount of fine, light-colored sand at the bottom, no invertebrates, clean fresh-looking middle-aged leaf located approximately halfway between newest and oldest leaves Plant: Little fungal vine on outside of trunk, located on a steep slope

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BBfrog4 8/1/12 4:40 pm Bloody Bay

1 adult Found sitting just above water level. Jumped away as I tried to take a picture.

Phytotelm: Water depth: .5cm (50% filled), no detritus although small amount of fine, light-colored sand at the bottom, no invertebrates, clean fresh-looking middle-aged leaf located slightly closer to the oldest leaves (17 cm from the ground) Plant: Plant growing out from under log on steep slope. Height of the plant was measured from the top of the log because of the extremely steep slope on the other side of the log.

BB5-41 8/2/12 9:30 am Bloody Bay

2 adults (1 male, 1 female)

One large male prominently placed just below the water level with head and forearms clearly visible. One female hiding beneath him wedged deeper in the phytotelm. Each climbed out of the phytotelm before leaping away while I took pictures. The contrast between the body shapes of the frogs when compared side by side allowed me to confidently label the sex of each individual (see Figure 3).

Phytotelm: Water depth: 3cm (50% filled), no detritus, no invertebrates, clean fresh-looking middle-aged leaf located closer to the newest leaves (18 cm from the ground) Plant: patch of white fungus on underside of leaf petiole

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BB5-43 8/2/12 9:55 am Bloody Bay

1 adult male Male fully submerged in the water of the phytotelm with head and forearms visible.

Phytotelm: Water depth: 3cm (50% filled), no detritus, clean fresh-looking middle-aged leaf located halfway between newest and oldest leaves (at a height of 72 cm) Plant: One large ant crawling between nearby leaf axils

BB5-44 8/2/12 10:15 am Bloody Bay

3 adults (1 male, 1 female, 1 unknown)

Male sitting above water level on the petiole of the leaf. One female submerged below water level with head and forearms visible. One unsexed individual wedged deeply into the base of the phytotelm. This third frog jumped out before I could properly observe its body shape.

Phytotelm: Water depth: 4cm (75% filled), no detritus, one beetle floating on the surface of the water, clean fresh-looking middle-aged leaf located closer to the newest leaves (19 cm from the ground) Plant: Nothing noteworthy

FR5-47 8/3/12 4:30 pm Forest Reserve

1 adult Found submerged in the water with head and forearms clearly visible. Hopped out before it could be sexed.

Phytotelm: Water depth: 3cm (50% filled), no detritus, no invertebrates, clean fresh-looking middle-aged leaf located approximately halfway between newest and oldest leaves Plant: Nothing noteworthy

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FRfrog1 8/3/12 5:25 pm Forest Reserve

1 adult female with several small but distinct lumps on her back

Seeking shelter in the phytotelm, hopped away before I could take a picture.

Phytotelm: Water depth: 4cm (75% filled), no detritus, no invertebrates, clean fresh-looking middle-aged leaf located approximately halfway between newest and oldest leaves Plant: Nothing noteworthy

FRfrog2 8/3/12 5:30 pm Forest Reserve

1 adult Submerged below water level with head and forearms clearly visible. Hopped out before it could be sexed.

Phytotelm: Water depth: 4cm (50% filled), no detritus, clean fresh-looking middle-aged leaf located approximately halfway between newest and oldest leaves Plant: Spider (>7mm) crawling between leaf axils