Filogeografia de la truita comuna (Salmo trutta) basada en la diversitat molecular del DNA mitocondrial

Abstract

The analyses performed in one hundred and ten brown trout (Salmo trutta) populations that cover its native European distribution, shows that the phylogenetic pattern is associated with the three major basins occupied by the species: Ponto-Caspian, Atlantic and Mediterranean. This differentiation is related with basin isolations during the Quaternary. The origin of the species is placed in the Ponto-Caspian region, in clear agreement with biogeographic models that postulates the Asian origin of European ichthyofauna. Further divergence occurred in the mid-lower Pleistocene generated the actual lineages: Atlantic and Duero in the Atlantic basin, Adriatic, Mediterranean and Marmoratus lineages in the Mediterranean rivers and the Danubian lineage in the Ponto-Caspian area. Pleistocene glacial periods have deeply modified the distribution range of brown trout, mainly in the Atlantic basin, where four major glacial refugia have been proposed: (i), at the East side of the ice sheet, (ii), in Central Europe, (iii), around the English Channel and (iv), around the Bay of Biscay. Only the three first seem to be involved in the recolonization of North Europe at the end of the last glacial period. The fourth glacial refugia, placed in Southern France and the Cantrabrian Sea area, would have been the origin of a southern expansion during Late Pleistocene. Nowadays, those trout populations are distributed in the Atlantic basin of the Iberian Peninsula. This glacial refugia could also be involved in older recolonizations of North-Europe previous to last glacial process. Brown trout population structure in areas at the Atlantic basin of the Iberian Peninsula is associated with river network. Thus, five trout population groups could be determined: trout from the Cantabrian Rivers, from the Miño River, from the Duero River, from the Tajo River and trout populations from the Guadalquivir basin. These last populations show a strong Mediterranean influence. In this basin, comparisons involving allozyme and mitochondrial DNA data are strongly correlated and points towards the same population groups. The rivers in the Mediterranean basin have been colonized by Adriatic and Mediterranean lineages, and strong secondary intergradations are reported among them during glacial periods. Population groups identified by allozyme and mitochondrial DNA do not agree as a consequence of this intergradation, as well as isolation and genetic drift during interglacial periods.