Hi everyone, We are offering a 6-month internship for a Master 2 student at the Evo-Eco-Paleo laboratory in Lille (France). Title of the traineeship: Effects of pollinator community composition on selection patterns Traineeship supervisor: Camille Jolivel, Isabelle De Cauwer & Nina Joffard Laboratory: UMR 8198 C Evo-Eco-Paleo, France (Lille) Phone number: 03 20 33 59 23 Email: camille.jolivel@univ-lille.fr, Isabelle.De-Cauwer@univ-lille.fr, nina.joffard@univ-lille.fr SUBJECT OF THE TRAINEESHIP The reproduction of generalist entomophilous angiosperms relies on their ability to attract different groups of pollinating insects through attractive signals (visual signals, olfactory signals, rewards for the pollinator). Phenotypic variation in these attractive signals is frequently observed within the same species, which can be explained by adaptation to the local pollination context. If phenotypic traits are heritable, selection pressures can lead to adaptation of these traits. Selection can be defined as the relationship between reproductive success (RS) and floral traits (Lande & Arnold 1983). For females, RS corresponds to the total number of seeds produced and for males, RS corresponds to the total number of seeds sired. Pollinator-mediated selection is considered an important part of the selection exerted on floral traits. However, when a plant is pollinated by various pollinators, these may exert different selection pressures on these traits, potentially leading to divergent evolution of floral traits within just a few generations (Gervasi & Schiestl 2017). Indeed, pollinators do not have the same sensory abilities or preferences (Fenster et al. 2004). Additionally, the morphological and behavioral characteristics of pollinators can significantly influence pollen export and deposition, and thus their pollination efficiency (Furtado et al. 2023). The optimal values of "mechanical" traits (i.e., traits related to the fit between the flower and the pollinator) should therefore differ from one group of pollinators to another. Silene dioica is a herbaceous, perennial, and dioecious angiosperm (i.e., species with separate sexes, Kay et al. 1984). S. dioica is pollinated by many different types of pollinators, and the composition of pollinator communities can vary, even at a small spatial scale ( 10 km). The aim of this internship is to generate genotyping data and to analyze the data collected during an experiment conducted in spring 2024, aimed at studying selection mediated by the most frequent diurnal pollinators of S. dioica, bumblebees and hoverflies. For this, three pollination treatments were set up under controlled conditions: the plants were exposed to bumblebees, or hoverflies, or both bumblebees and hoverflies. The objectives are to: (1) determine which floral traits are selected and with what intensity, for each treatment, (2) determine whether the presence of both pollinators results in non- additive selection (total selection does not correspond to the sum of the selection mediated by each pollinator, terHorst 2017). During the experiment, several floral traits were measured on each individual (corolla width, calyx height, number of open flowers, number of flowers produced, and plant height). Pollinator visit observations were conducted to study the activity of each pollinator type. To estimate the reproductive success (RS) of each individual, all the seeds produced during the experiment were collected. For female, RS will be estimated as the total number of seeds produced. For males, RS will be estimated by the total number of seeds sired. To estimate this quantity, genotyping of a subsample of seeds produced during the experiment will be performed. The DNA of each adult will be extracted from a leaf sample, and the DNA of the offspring will be extracted directly from the seeds. Paternity analyses will then be conducted. Finally, directional selection gradients will be estimated using the method of Lande & Arnold (1983). References : - Fenster, C. B., Armbruster, W. S., Wilson, P., Dudash, M. R., & Thomson, J. D. (2004). Pollination syndromes and floral specialization. Annual Review of Ecology, Evolution, and Systematics, 35(1), 375-403. - Furtado, M. T., Matias, R., P¨¦rez©\Barrales, R., & Consolaro, H. (2023). Complementary roles of hummingbirds and bees: Pollen pickup, pollen deposition, and fruit production in the distylous Palicourea rigida. American Journal of Botany, 110(6), e16194. - Gervasi, D. D. L., & Schiestl, F. P. (2017). Real-time divergent evolution in plants driven by pollinators. Nature Communications, 8(1), 14691. - Kay, Q. O. N., Lack, A. J., Bamber, F. C., & Davies, C. R. (1984). Differences between sexes in floral morphology, nectar production and insect visits in a dioecious species, Silene dioica. New Phytologist, 98(3), 515 529. - Lande, R., & Arnold, S. (1983). The measurement of selection on correlated characters. Evolution, 1210 1226. - terHorst, C. P., Lau, J. A., & Conner, J. K. (2017). Quantifying nonadditive selection caused by indirect ecological effects: Reply. Ecology, 98(4), 1171-1175. Camille Jolivel (to subscribe/unsubscribe the EvolDir send mail to golding@mcmaster.ca)