Assessing inter‐drainage connections: patterns of genetic diversity in an I berian cyprinid fish

The phylogeography of I berian freshwater fish species strongly reflects the geomorphological history of I berian water drainages and formation of mountain ranges. In particular, the I berian C entral M assif limits two ichthyogeographical districts based on fish distribution assemblages: the N orthwest district, which comprises all river basins north of the C entral massif, and the C entral‐west district, which comprises the T ejo and S ado basins. Despite this scenario, the cyprinid P seudochondrostoma polylepis occurs in both the T ejo and M ondego rivers (one either side of the E strela M ountains, in the western end of the C entral M assif). By analysing the population structure and demographic history of this straight‐mouth nase, based on both mt DNA and microsatellites, we have found evidence of a relatively recent common origin for both M ondego and T ejo populations. Shared haplotypes and lack of divergent lineages for mitochondrial marker, high levels of admixture and common ancestry at the nuclear level, together with signatures of asymmetrical gene flow from T ejo to M ondego suggest a M ondego colonization through a founder event with an origin in T ejo. We suggest that this colonization might have resulted from the occurrence of river connections/captures between M ondego and T ejo headwater tributaries in the recent past. With this study we reinforce that local‐scale geomorphological events and the adaptation/dispersal ability of a species to new environments can have a major impact on its demographic history, colonization processes, and ultimately its distribution. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society , 2013, 109 , 656–669.