TY - JOUR T1 - Population genetics reveals cryptic lineages and ongoing hybridization in a declining migratory fish species complex JF - bioRxiv DO - 10.1101/2021.12.04.471201 SP - 2021.12.04.471201 AU - Quentin Rougemont AU - Charles Perrier AU - Anne-Laure Besnard AU - Isabelle Lebel AU - Yann Abdallah AU - Eric Feunteun AU - Elodie Réveillac AU - Emilien Lasne AU - Anthony Acou AU - David José Nachon AU - Fernando Cobo AU - Guillaume Evanno AU - Jean-Luc Baglinière AU - Sophie Launey Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/12/04/2021.12.04.471201.abstract N2 - Deciphering the effects of historical and recent demographic processes responsible for the spatial patterns of genetic diversity and structure is a key objective in evolutionary and conservation biology. Using genetic analyses, we investigated the demographic history, the contemporary genetic diversity and structure, and the occurrence of hybridization and introgression, of two species of anadromous fish with contrasted life history strategies and which have undergone recent demographic declines, the allis shad (Alosa alosa) and the twaite shad (Alosa fallax). We genotyped 706 individuals from 20 rivers and 5 sites at sea in Southern Europe at microsatellite markers. Genetic structure between populations was lower for the nearly semelparous species allis shad that disperse stronger distance compared to the iteroparous species, twaite shad. Individuals caught at sea were assigned at the river level for twaite shad and at the region level for allis shad. Using an approximate Bayesian computation framework, we inferred that the most likely long term historical divergence scenario between both species implicated historical separation followed by secondary contact accompanied by strong population size decline. Accordingly, we found evidence of contemporary hybridization and introgression between both species. Besides, our results support the existence of cryptic species in the Mediterranean sea. Overall, our results shed light on the interplay between historical and recent demographic processes and life history strategies in shaping population genetic diversity and structure of closely related species. The recent demographic decline of these species’ populations and their hybridization should be carefully considered while implementing conservation programs.Competing Interest StatementThe authors have declared no competing interest. ER -