A PhD position is open in the Teotónio lab at the Institut de Biologie de l'École Normale Supérieure (IBENS), in Paris, France (https://www.ibens.bio.ens.psl.eu/?rubrique28); as part of a collaborative research project between the host lab and that of Christian Braendle at the Institut de Biologie de Valrose in Nice, France (http://ibv.unice.fr/research-team/braendle/). Genetic assimilation describes the evolutionary process during which an environmentally-induced phenotype becomes a genetically encoded phenotype. This important concept remains controversial because the molecular mechanisms of genetic assimilation are rarely understood. This project will characterize genetic assimilation of environmentally induced egg retention in the nematode Caenorhabditis elegans at the molecular level. We will use genome-wide association mapping to identify molecular variants involved in genetic assimilation during experimental evolution. To study the functional consequences of these variants on egg laying, we will employ CRISPR-Cas9 gene editing, tissue-specific reporter genes, and mosaic analysis. The evolutionary history of identified variants will be tracked across replicate populations over 100 generations of experimental evolution. Finally, we will extend our molecular analyses from experimental to natural populations to understand how these variants influence the environmental sensitivity of the egg-laying circuit in wild C. elegans. Candidates are expected to have a master's degree or equivalent in evolutionary biology and an excellent understanding of the fundamental problems of quantitative genetics and population genetics, including QTL and GWAS mapping. Candidates with experience in model organism handling, computer programming, experimental evolution and statistical analysis of large data sets are preferred. The PhD project may involve the use of genetic transformation methods, so experience with molecular and developmental biology techniques is a plus. The PhD student will be expected to conduct full-time independent research in the Teotónio lab. The PhD position, including social benefits, is funded by the National Agency of French Research (ANR MolAssim) for three years, with a potential one-year extension. Successful applicants can start their PhD as soon as November 2025. To apply, please send a single PDF file containing your CV, a letter of motivation, and the contact information of two referees to Henrique Teotónio (teotonio@bio.ens.psl.eu). Use the subject line: PhD_MolAssim_YOURNAME. Informal inquiries are welcome. Applications will be accepted until 19 September 2025, and shortlisted candidates will be interviewed (in person or online) during the week of 29 September - 3 October. Relevant background findings: Dey et al. 2016. doi:10.1371/journal.pbio.1002388.s008 Noble et al. 2017. doi: 10.1534/genetics.117.300406 Teotónio et al. 2017. doi: 10.1534/genetics.115.186288 Vigne et al. 2021. doi: 10.1126/sciadv.abd9941 Mignerot et al. 2023. doi:10.7554/elife.88253 Fausett et al. 2023. doi:10.1038/s41467-023-38527-0 Henrique Teotónio, Professor Experimental Evolutionary Genetics Institut de Biologie de l'ENS 46 Rue d'Ulm 75005 Paris, France https://www.ibens.ens.fr/?rubrique28 Henrique Teotónio (to subscribe/unsubscribe the EvolDir send mail to golding@mcmaster.ca)