Thermal reactionomes reveal divergent responses to thermal extremes in warm and cool-climate ant species

Background: The distributions of species and their responses to climate change are in part determined by their thermal tolerances. However, little is known about how thermal tolerance evolves. To test whether evolutionary extension of thermal limits is accomplished through enhanced cellular stress response (enhanced response), constitutively elevated expression of protective genes (genetic assimilation) or a shift from damage resistance to passive mechanisms of thermal stability (tolerance), we conducted an analysis of the reactionome: the reaction norm for all genes in an organism\u27s transcriptome measured across an experimental gradient. We characterized thermal reactionomes of two common ant species in the eastern U.S, the northern cool-climate Aphaenogaster picea and the southern warm-climate Aphaenogaster carolinensis, across 12 temperatures that spanned their entire thermal breadth. Results: We found that at least 2 % of all genes changed expression with temperature. The majority of upregulation was specific to exposure to low temperatures. The cool-adapted A. picea induced expression of more genes in response to extreme temperatures than did A. carolinensis, consistent with the enhanced response hypothesis. In contrast, under high temperatures the warm-adapted A. carolinensis downregulated many of the genes upregulated in A. picea, and required more extreme temperatures to induce down-regulation in gene expression, consistent with the tolerance hypothesis. We found no evidence for a trade-off between constitutive and inducible gene expression as predicted by the genetic assimilation hypothesis. Conclusions: These results suggest that increases in upper thermal limits may require an evolutionary shift in response mechanism away from damage repair toward tolerance and prevention

The Effect of Plant Inbreeding and Stoichiometry on Interactions with Herbivores in Nature: Echinacea angustifolia and Its Specialist Aphid

Fragmentation of once widespread communities may alter interspecific interactions by changing genetic composition of interacting populations as well as their abundances and spatial distributions. In a long-term study of a fragmented population of Echinacea angustifolia, a perennial plant native to the North American prairie, we investigated influences on its interaction with a specialist aphid and tending ants. We grew plant progeny of sib-matings (I), and of random pairings within (W) and between (B) seven remnants in a common field within 8 km of the source remnants. During the fifth growing season, we determined each plant's burden of aphids and ants, as well as its size and foliar elemental composition (C, N, P). We also assayed composition (C, N) of aphids and ants. Early in the season, progeny from genotypic classes B and I were twice as likely to harbor aphids, and in greater abundance, than genotypic class W; aphid loads were inversely related to foliar concentration of P and positively related to leaf N and plant size. At the end of the season, aphid loads were indistinguishable among genotypic classes. Ant abundance tracked aphid abundance throughout the season but showed no direct relationship with plant traits. Through its potential to alter the genotypic composition of remnant populations of Echinacea, fragmentation can increase Echinacea's susceptibility to herbivory by its specialist aphid and, in turn, perturb the abundance and distribution of aphids

Writing in Britain and Ireland, c. 400 to c. 800

No abstract available

README for Tassel analysis

PDF file that describes how Tassel analysis was performed, and analysis of resulting data with R script

R functions for Tassel analysis

Functions required by R for analysis of Tassel result

shell script for Tassel analysis

Portable Bash System (PBS) shell script for Tassel analysis run on Minnesota Supercomputing Institute server

R script for Tassel analysis

R script called by PBS shell script to analyse results of Tasse

Estimation of repeatability for Medicago truncatula phenotypic data

<p>Estimation of clonal repeatability, an upper-bound on heritability, for replicated accessions of Medicago truncatula grown in a greenhouse. Accompanies paper "Estimating heritability using genomic data" by J. Stanton-Geddes et al. (in press) <em>Methods in Ecology and Evolution. </em></p> <p>The data used in this script is available on DataDryad: http://datadryad.org/resource/doi:10.5061/dryad.pq143</p

Patterns of thermal stress tolerance vs. resistance in genome-wide expression data of parapatric ant species

<p>Presentation given at the 2014 Evolution Conference in Raleigh, NC. </p

Data from: Does a facultative mutualism limit species range expansion?

The availability and quality of mutualists beyond a species’ range edge may limit range expansion. With the legume Chamaecrista fasciculata, we asked to what extent the availability and quality of rhizobia beyond the range edge limits host range expansion. We tested the effect of rhizobia availability on plant growth by transplanting seed from three locations into five sites spanning C. fasciculata’s range (interior, at the northern and western range edges, and beyond the range edges), and inoculating half the seeds with rhizobia. We recorded growth of all surviving plants, and for the uninoculated plants, whether they had formed nodules or not. We isolated rhizobia from nodules collected on the uninoculated plants, and cross-inoculated seed from four populations (both range edge and interior populations) in the greenhouse to determine whether the quality of rhizobia differed between regions. We found that seeds transplanted beyond the range edge were less likely to be nodulated when they were not experimentally inoculated, and there was benefit to inoculation at all sites. In the greenhouse, the three inocula that formed nodules on plants, from the range interior, northern edge and beyond the northern edge, did not detectably differ in their effect on plant growth. These results suggest that low densities of suitable rhizobia beyond the range edge may limit range expansion of legume species