Complex patterns of within- and between-drainage gene flow in wild population of guppies
Blondel L., Baillie L., Quinton J., Alemu J., Paterson I.G., Hendry A.P., Bentzen P.
MCGILL UNIVERSITY

Population genetic structure for a given species in a given geographic region can be shaped by both historical and contemporary patterns of gene flow. However, the relative importance of these two processes is poorly understood. In the present study, we investigated patterns of neutral genetic variation as well as adaptive traits in multiple populations of wild guppies in two watersheds in northern Trinidad. We found evidence of within, but also cross drainage gene flow using STRUCTURE and MIGRATE, suggesting that classic riverine connectivity scenario is complicated by other factors. We thus estimated divergence time between upstream and downstream pairs of populations from each drainage using DIYABC, and found great variation in estimates, suggesting either geological events causing exchanges or human transferred fish between watersheds. Following a Discriminant Analysis on principal components (DAPC), historical or contemporary gene flow in our study showed to have no obvious signature on adaptive trait variation, emphasizing the importance of divergent natural and sexual selection as primary drivers of trait variation in guppies.