Plant-animal interactions
description
Transcript of Plant-animal interactions
Plant-animal interactions• Co-evolution?• Herbivory• Plant defense• Pollination• Seed dispersal• Interactions across
the life cycle• Conservation:
butterflies/host plants
Photos: Ricklefs (Economy of Nature), Bradshaw & Schemske, Kalko, http://www.inriodulce.com/links/ants.html
TODAY: Coevolution
• Definitions and issues– Species Interactions– Evolution by natural selection– Fitness– Coevolution?• Pairwise• Diffuse• Geographic mosaic
• Examples (a few)
SPECIES INTERACTIONS
+/- consumer-resourcepredator-prey, parasite-host, plant-herbivore
- /- competition+/+ mutualism
trophic, seed dispersal, pollination, defense
Interacting species may coevolve
Biotic selective agents evolve
Species act as selective agents on each other’s traits
Trait A→A’
Trait X→X’
Biological SELECTIVE Agents
• biological factors stimulate mutual evolutionary responses
• adaptations of organisms in response to changes in the physical environment have no effect on that environment
• biological agents foster diversity• physical agents foster convergence
EVOLUTION by natural selection
• Selection= non random association of FITNESS with traits
• Response to selection(IF there is a genetic basis to traits)
= CHANGE IN GENE FREQUENCY ACROSS GENERATIONS
andCHANGE IN TRAIT DISTRIBUTION
ACROSS GENERATIONS
FITNESS• Representation of your
stuff in the future – Send yourself– Send your offspring
• Survival and reproduction both determine your contribution to genes (and trait distributions) in future population
COEVOLUTION(in the strict sense, Janzen 1980)
• populations of• two or more species interact, • traits of each may evolve in
response to traits of the other • reciprocal selective effects on
traits
Coevolution or Association?
• The term “coevolution” has sometimes been used broadly
• the close association of certain species and groups of species in biological communities, but…
Pairwise or Diffuse Coevolution?• Do pairs of species undergo
reciprocal evolution or• do “coevolved” traits arise as
responses of populations to selective pressures exerted by a variety of species, followed by ecological sorting?
• Are species organized into interacting sets based on their adaptations, coevolved or not?
Classic references• Charles Mode (1958) coined the term
coevolution– host and pathogen: cycling of
virulent/avirulent pathogens and susceptible/resistant hosts
• Paul Ehrlich and Peter Raven (1964) placed coevolution into an ecological context– closely related groups of butterflies tend to
feed on closely related species of plants– specialization is associated with host plant
chemistry
Geographic Mosaic Theory(Thompson 2005)
Geographic selection mosaics: selection varies among populations because there are geographic differences in how fitness in one species depends upon the distribution of genotypes in another species
Coevolutionary hotspots: Interactions are subject to reciprocal selection only within some communities. Broader matrix of coevolutionary coldspots, (where selection is non-reciprocal or where only one of the participants occurs).
Trait remixing: The genetic structure of coevolving species changes through new mutations, gene flow across landscapes, random genetic drift, and extinction of local populations (shifting geographic mosaic of coevolution). http://bio.research.ucsc.edu/people/thompson/Research.html
TODAY: Coevolution
• Definitions and issues– Species Interactions– Evolution by natural selection– Fitness– Coevolution?• Pairwise• Diffuse• Geographic mosaic
• Examples (a few)
Heliconius butterflies have big eyes
The caterpillars feed on Passiflora leaves…
HERBIVORY
Passiflora leaf shapes and egg mimics are defensive against a visual herbivore
HERBIVORY
Everything is connected: Other vines the rainforest are pollinated by Heliconines!
• Anguria and Gurania in squash family• high canopy vines• bright, red tubular flowers with a
bright yellow marking the center• Heliconius get pollen… using amino
acids in egg production• Very specialized• What about Florida firebush?
Photos: http://www.infojardin.com, http://www.mittanbotanicalgardens.com/shrubs.htm
Mimicry complexM. marsaeusM. menophilus
M. ludovica
Northern Peru
throughoutSouthAmerica
Butterflies and host chemistry(Ehrlich and Raven 1964)
• Papilionidae– Papilio: Rutaceae, Umbelliferae &
coumarins
• Pieridae– Pierinae: Capparidaceae, Cruciferae &
mustard oil glucosides
• Nymphalidae– Danainae: Apocynaceae, Asclepiadaceae
& milky juice w/bitter glycosides
• Libytheidae: Ulmaceae, Rosaceae & ?
• Lycaenidae: – Lycaenini: diverse families, ant-defended
Photos:http://bugguide.net/node/view/118252/bgimage, http://thelifeofyourtime.wordpress.com/page/11/, http://www.naba.org/chapters/nabast/MonarchMilkweedSolar41705gq.jpg, http://myrmecos.net/ants/Lycaena22.JPG
HERBIVORY
The carrot familyincludes Queen Anne’s Lace,celery, cilantro,parsley, dill….
Berenbaum found:
Evolutionary historyof the chemistry :increasing complexityand increasing toxicityand increasinglyspecialized occurrence
ONLY highly specialized insects feed on the mosttoxic ones
These are descended from close relatives thatfeed on less toxic ones
Insect families such as Swallowtail butterflies, that feed on carrot family also feed on distantly relatedCitrus family…
Which also has furanocoumarins!
Many plants…subset of these…subset of these
Papilio thoas from Peru
HERBIVORY
Mutualism (+/+): Interactions between species that benefit both participants
• Trophic– lichen: partnership between algae and fungi– Rhizobium-plants– Mycorhizzae-plants– wood digesters in rumens…bacteria within
ciliates
• Defensive– ant-plants
• Dispersive– pollinators-plants– seed dispersers-plants
Trophic Mutualism
• Trophic mutualisms usually involve partners specialized for obtaining energy and nutrients
Defensive Mutualism
• Defensive mutualisms involve species that receive food or shelter from their partners in return for a defensive function
Dispersive Mutualism
• Dispersive mutualisms involve animals that:– transport pollen in return
for rewards such as nectar
– transport and disperse seeds in return for the nutritional value of fruits or other structures associated with seeds
Mimulus lewisii Bumblebee
Mimulus cardinalis Hummingbird
• Experimental genetics
• Hybrid genotypes in field assays
• One gene (YUP) swap = change in pollinator?
POLLINATION
Yuccas (Yucca) Yucca moths (Tegeticula)
• mutually beneficial• obligate for both partners• phylogenetic analysis• moth behaviors selected
by plants or pre-adapted?
POLLINATION
Moth larvae have no other food source and yucca plants have no other
pollinator...• adult female yucca moths carry balls of pollen
between yucca flowers by means of specialized mouthparts
• during pollination, the female moth deposits eggs in the ovary of the yucca flower
• after the eggs hatch, the developing larvae feed on some of the developing yucca seeds, not exceeding 30% of the seed crop
• the yucca exerts selective pressure on the moths (through abortion of heavily infested fruits) to limit moth genotypes predisposed to lay large numbers of eggs (cheaters)
Is the Yucca/Yucca Moth Mutualism Coevolutionary?
• Many aspects of the mutualism are present in the phylogenetic lineage of nonmutualistic moths within which Tegeticula evolved– host specialization and mating on the host
plant– traits present in the moth lineage before the
establishment of the mutualism itself,– evidence for preadaptation– what appear to be coevolved traits may have
been preadaptations that were critical to establishment of the mutualism in the first place
phylogenetic analysis
Geographic mosaic: +/+ or +/- ?Greya politella: friend or foe to Lithofragma parviflorum?
Photo: http://bio.research.ucsc.edu/people/thompson/HQImages.html, data Thompson and Cunningham 2002
Summary…idea of coevolution
• Interactions among species are major sources of selection
• Coevolution is the interdependent evolution of species that interact ecologically
• Consumer-resource systems give abundant examples: host-pathogen, host-parasitoid, plant-herbivore..
Summary: mutualisms• Mutualisms are relationships between species
that benefit both.• Mutualisms may be trophic, defensive, or
dispersive.• Phylogenetic analysis helps infer the
evolutionary history of interspecies interactions• Experimental genetics in the field can reveal how
plant-animal interactions select for different genes and trait distributions
• Identification of coevolved relationships is difficult, preadaptations and geographic mosaics may complicate evolutionary interpretation