Genomic and phenotypic differences in Caenorhabditis elegans isolated from different habitats

Genomic and phenotypic differences in Caenorhabditis elegans isolated from different habitats Rita J Volkers¹, Basten L Snoek¹, Joost Riksen¹, Hinrich Schulenburg², Bart Braeckman³, Jan E Kammenga¹ 1Wageningen University, Nematology, Wageningen, 6708PB, Netherlands, ²Christian-Albrechts-University of Kiel, Evolutionary Ecology and Genetics, Kiel, 24118, Germany, ³Ghent University, Biology, Ghent, B-9000, Belgium Local populations of C. elegans are genetically diverse and low frequency of out-crossing allows for the recombination of these locally diverse genotypes. Environmental challenges may cause a fitness reduction and therefore impose selection on the affected populations. Two main responses are possible. i) A phenotypic plastic response in which selection favored adaptation to environmental factors by adjusting metabolic processes or specific behaviors. Adaptation is thus determined at the non-genetic level (i.e. at the transcriptomic or proteomic level); ii) an evolutionary response in which selection directly acts on the genetic composition of the population as a consequence of differential mortality and reproductive success. Adaptation to the environmental challenge is thus manifested genetically within the population. Yet, we currently lack any understanding concerning adaptive responses in C. elegans to environmental conditions. Here we evaluate the importance of the two adaptive responses and the underlying genomic architecture, using 40 natural populations derived from different habitats and locations in France (kindly provided by M-A Félix). Half of them were isolated from rotting apples in Orsay and the other half from rotting hogweed stems in Santeuil. As an out-group we used 3 newly isolated Dutch strains. We found that populations from the two habitats could be distinctively separated by genotypic differences as well as differential genome-wide gene expression levels and various life-history traits. Currently we investigate the response to locally associated bacteria and the possible genetic adaptations to these different bacteria. Together our results will lead to a more complete understanding of the adaptation and evolution of C. elegans. This work is supported the European Science Foundation (ESF): NEMADAPT - Molecular architecture of environmental adaptation in natural populations of the nematode Caenorhabditis elegans.