RESUMEN
Genetic diversity and colonization routes of noble salmons were studied using a partial nucleotide sequence of the mitochondrial COI gene. The brown trout S. trutta, which is the most ancient species of the genus, was concluded to originate from the modern southeastern Pontic-Caspian area, which is currently inhabited by members of the subspecies S. trutta oxianus. Migrating westward while the Paratethys was in existence (5-34 million years ago), species of the genus colonized ancient water bodies in the modern Mediterranean basin and formed many isolated populations that survived desiccation of the Mediterranean Sea (5-6 million years ago). The Strait of Gibraltar mediated brown trout migrations to Northern Europe; the subspecies S. trutta trutta belongs to a relatively young phylogenetic lineage of the species. A separate brown trout lineage, currently classified as the subspecies S. trutta labrax, formed most likely in the area of the modern Danube basin, which was a relatively separate part of the Paratethys and was sometimes isolated as the Pannonian Lake. A highly divergent phylogenetic lineage of Atlantic salmon (S. salar) haplotypes originates from a haplotype of the brown trout that inhabited the area of the modern Strait of Gibraltar.
Asunto(s)
Salmo salar/fisiología , Migración Animal , Animales , Evolución Biológica , ADN Mitocondrial/genética , Complejo IV de Transporte de Electrones/genética , Europa (Continente) , Genes Mitocondriales , Variación Genética , Haplotipos , Salmo salar/clasificación , Salmo salar/genéticaRESUMEN
The phylogenetic relationships of 492 chub (Leuciscus cephalus) belonging to 89 populations across the species' range were assessed using 600 base pairs of cytochrome b. Furthermore, nine species belonging to the L. cephalus complex were also analysed (over the whole cytochrome b) in order to test potential allopatric hybridization with L. cephalus sensu stricto (i.e. the chub). Our results show that the chub includes four highly divergent lineages descending from a quick radiation that took place three million years ago. The geographical distribution of these lineages and results of the nested clade analysis indicated that the chub may have originated from Mesopotamia. Chub radiation probably occurred during an important vicariant event such as the isolation of numerous Turkish river systems, a consequence of the uplift of the Anatolian Plateau (formerly covered by a broad inland lake). Dispersion of these lineages arose from the changes in the European hydrographic network and, thus, the chub and endemic species of the L. cephalus complex met by secondary contacts. Our results show several patterns of introgression, from Leuciscus lepidus fully introgressed by chub mitochondrial DNA to Leuciscus borysthenicus where no introgression at all was detected. We assume that these hybridization events might constitute an important evolutionary process for the settlement of the chub in new environments in the Mediterranean area.