Evolutionary Biology BOIL 2662

Prepare a critical commentary on your readings. This should consist of a summary of the main subject matter, comments on where future research is likely to lead (or things that we still do not know), as well as any remarks on limitations or weaknesses in the research. Chose two out of the four listed and type 3 pages based on the two research articles chosen. Due Thursday 10th October, 2013 at 4 pm

Papers Chosen

Wilf 2008 (main paper)

http://myelearning.sta.uwi.edu/mod/resource/view.php?id=323678

Wilf 2008

http://myelearning.sta.uwi.edu/mod/resource/view.php?id=323677

Peter Wilf uses fossil plants to investigate ancient ecosystems, past environmental

change, and the evolution and extinction of plants and plant-insect associations. He

emphasizes questions with relevance for modern climate change, biodiversity,

biogeography, and ecological processes. His principal field areas included Patagonia,

Argentina, and the Western Interior USA. In the two papers reviewed Wilf (2008a) and

Wilf (2008b), in the first paper the author focused on flowering plant fossil leaves to

determine its usefulness for paleoclimate estimates. In the second paper a follow up of

the first, studies leave fossils and the plant-insect associations to understand ancient

climate change and extinction.

In Wilf (2008a) paper, he focused on a selection of developing research areas where

fossil angiosperm leaves can play a central role. This was done by discussing the

legacy issues in identifying angiosperms because of their high diversity, abundance and

phenotypic plasticity from Cretaceous to Recent. The reason this was of importance

was because the literature was filled with thousands of apparently intractable

assignments to extant genera based on superficial comparisons. He then look at ways

on how to overcome them as an important and interesting research goal, combining

subdisciplines that often work separately. He also provided an overview of recent

developments, in plant functional ecology, paleoclimate, and plant-animal interactions,

that have much potential to provide important new links between paleoecology and

neoecology.

Wilf (2008a) saw an opportunity to re-evaluate angiosperm leaf architecture within the

overhauled phylogenetic context offered by molecular data. He indicated that the

phylogenetic signal, homoplasy, and character evolution of leaf architecture can be

investigated quantitatively, and this should eventually lead to greater confidence in the

phylogenetic significance of particular characters when they are found in fossils. On the

other hand whilst this method was useful, the bulk of taxa, especially from older

(Cretaceous and Paleogene) floras will remain unidentified for some time to come,

especially because the discovery rate of new forms remains high.

In this study Wilf (2008a) recommended the use of morphototyping with a combitation of

systematics methods to drive his project. He strongly believe even with the contentions

associated with morphototyping among botanists and paleobotanists, the collaboration,

cooperation and diversification of interest is a robust recipe for diverse successes.

They have collected more than 12,000 plant fossils with precise stratigraphic control,

including more than 400 leaf morphotypes, to answer a set of initial questions about

plant diversity, plant-insect associations, paleoclimate, and geochronology. At the same

time, the collections allow systematic delineation of many important botanical entities,

usually based on leaves with cuticles or attached or associated reproductive structures

as well as new ichnotaxonomic entities from fossilized insect folivory.

Wilf (2008a) found that insect Damage Types (DTs) parallel leaf morphotypes in many

ways in terms of taxonomic issues. They are informal, operational units that represent

the insect-feeding richness on a flora. Although some may find the inherent concept of

“morphotypes on morphotypes” unsettling, this allows characterization of the full

spectrum of damage richness on all the host plants in a flora. As for leaf morphotypes,

the eventual incorporation of DTs into formal taxonomic entities is essential, especially

for those that can be linked to a well-defined culprit but the discovery rate is much

higher than the description rate. A major difference from leaf morphotypes, which

usually correspond to inferred species entities, is that the correspondence of DTs to real

herbivore species is highly variable, and for the most part unquantified. Whereas the

mine, gall, and other “specialized” damage types on a particular plant host typically

each represent one or only a few herbivore species generalized feeding, such as most

external foliage feeding, is much harder to pinpoint. A few herbivore species at a site

may make many kinds of damage on many plant species. Therefore, a major effort is

needed in living forests to calibrate the insect damage types to the number of herbivore

species that make them. This work was done on his second paper that leads to more

informed interpretations of fossil damage occurrences and also produces important

natural history data. Moreover he also found a great potential for reinvestigating leaf

fossils with epifluorescence microscopy as well.

In the second paper Wilf (2008b) indicated that fossil record, foliage with well-preserved

insect damage often offers abundant and diverse information both about producers and

about ecological and sometimes taxonomic groups of consumers. These data are

ideally suited to investigate food web response to environmental perturbations, and they

represent an invaluable deep-time complement to neoecological studies of global

change. Wilf (2008b) had three hypotheses :

Hypothesis 1. Insect-feeding diversity and frequency correlate with temperature

Hypothesis 2. Insect-feeding diversity and frequency increase in variance with

decreased rainfall and associated changes in leaf traits

Hypothesis 3. Insect-feeding diversity tracks plant diversity

His studied showed that correlations between feeding diversity and temperature,

between herbivory and leaf traits that are modulated by climate, and between insect

diversity and plant diversity can all be investigated in deep time. To illustrate this he

emphasize recent work on the time interval from the latest Cretaceous through the

middle Eocene (67–47 million years ago (Ma)), including two significant events that

affected life: the end-Cretaceous mass extinction (65.5 Ma) and its ensuing recovery;

and globally warming temperatures across the Paleocene–Eocene boundary (55.8 Ma).

Climatic effects predicted from neoecology generally hold true in these deep-time

settings. His second hypothesis showed that rising temperature is associated with

increased herbivory in multiple studies, a result with major predictive importance for

current global warming. The third hypothesis showed that diverse floras are usually

associated with diverse insect damage; however, recovery from the end-Cretaceous

extinction reveals uncorrelated plant and insect diversity as food webs rebuilt chaotically

from a drastically simplified state. Calibration studies from living forests are needed to

improve interpretation of the fossil data.