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Genetic and epigenetic basis of adaptation to climate change

Final Report Summary - GEBACC (Genetic and epigenetic basis of adaptation to climate change)

A pressing question in modern biology is how quickly natural populations can respond to anthropogenic selection pressures. Integral to predicting evolvability will be an understanding of the contributions of genetic adaptation and phenotypic plasticity to this response and of the molecular changes associated. Indeed, although there is growing appreciation that phenotypic plasticity might play an important role in the evolution and spread of adaptive phenotypes, ultimately evolution requires adaptive changes in gene frequencies. The project GEBACC was set up to test the ability of wild populations to respond to human-induced environmental changes by investigating the response to selection on an ecologically-relevant trait (locomotion) in a wild-caught amphibian, xenopus tropicalis, a model system in developmental genetics. Amphibians are among the most endangered taxa of the current 6th extinction, with over a third of species threatened globally. Habitat fragmentation and loss are a major cause of amphibian decline and impact around 90 % of species threatened. In particular, tropical forests, which contain a majority of all amphibians, are rapidly shrinking as a result of logging. Such habitat change is predicted to favour individuals with strong locomotor abilities that are able to disperse to novel habitats of suitable quality. This project aimed to recreate this selection event, under controlled laboratory condition, by selectively breeding x. tropicalis for increased endurance under different temperature (optimal and high) and to monitor the genetic, epigenetic, physiological, biochemical and morphological changes associated with the response to selection, as well as measure the impact of selection on other fitness related traits (immunity). Indeed, given that natural populations almost always face a multiplicity of threats simultaneously, yielding several, often divergent, selection pressures and because amphibians are currently threatened worldwide by an emerging infectious disease (chytridiomycosis), it is important to evaluate to what extent the response to one selection pressure affects the response to another and hence the role of tradeoffs in the response to selection.

In the last two and a half years (excluding my maternity leave) since the start of the project late 2009, I have successfully established a wild-caught breeding population of xenopus tropicalis frogs which I have brought back from Cameroon. I have collected whole-organismal as well as tissue-level data on the locomotor abilities in these frogs. This work has already given rise to four publications (Herrel and Bonneaud Journal of Experimental Biology 2012a; Herrel and Bonneaud Journal of Experimental Biology 2012b; Herrel, Gonwouo, Fokam, Ngundy, and Bonneaud Journal of Zoology 2012; James, Tallis, Herrel and Bonneaud Journal of Experimental Biology 2012). However, in mid 2011, the frogs had to be transferred to a new facility at the National Museum of Natural History in Paris due to problems with the set-up at the Station d' Ecologie Expérimentale in Moulis. For this reason, I have only just recently started to selectively breed the frogs again based on their locomotor ability; this breeding programme has currently been halted.

Given the difficulties encountered with x. tropicalis, I initiated a collaboration with Dr Michel Baguette (MNHN) and Prof. Jean Clobert (CNRS), both at the Station d' Ecologie Experimentale, to investigate similar questions as the ones proposed in GEBACC, but this time using model systems in ecology and evolution: a butterfly (pieris brassicae) and a lizard (lacerta vivipara). Dr Baguette and his postdoc, Dr Delphine Legrand, are in charge of catching wild butterflies, phenotyping them for locomotor ability (endurance) and selectively breeding them for increased endurance. We have already successfully obtained one generation and I am now poised to examine the association between expression patterns of candidate genes and phenotypic differences, as well as the heritability of endurance. While Dr Legrand is helping run candidate gene assays, I am about to sequence the full transcriptome of individuals of extreme phenotypes (using Illumina next-generation sequencing technology) from a complementary deoxyribonucleic acid (cDNA) library that I constructed, with the goal of generating a reference transcriptome on which future transcriptome-wide gene expression studies will be based.

Early 2012, I successfully secured a permanent lectureship position at the very prestigious University of Exeter, United Kingdom (UK), which was to start on 1 September 2012; the University of Exeter has very recently joined the Russell group of leading research-led universities in the UK and has been named 'University of the year' by the Sunday Times. This excellent news was however dampened in August 2012, when I suddenly found out that my Marie Curie funding was going to be unexpectedly cut back by 35 % as a result of my move to Exeter and that I would not be getting the remaining EUR 35 937.50 that I had been awarded end of 2009. While I cannot understand the logic of cutting funding over half way into a project, this means that I no longer have the anticipated funds to cover the costs of all the remaining work planned. As a result, I am unable to finish off the genomics analyses, as well as obtain bioinformatics support to analyse the data obtained so far. Thus all the work achieved so far and all the publications resulting from this work and currently in preparation have been put on hold indeterminately.