MITOCHONDRIAL-DNA SEQUENCE VARIATION AND PHYLOGEOGRAPHY AMONG SALMO-TRUTTA L (GREEK-BROWN TROUT) POPULATIONS

To investigate the phylogenetic relationships and geographical structu re among brown trout S. trutta L. populations from the South Adriatic- Ionian and Aegean sea basins, mitochondrial DNA nucleotide sequence co mparisons were used. A 310-base-pair (bp) segment of the control regio n (D-loop), and an additional 280-bp segment of the cytochrome b gene were sequenced from representatives of 13 brown trout populations. Phy logenetic analyses, conducted after combining the data presented with published data from other Eurasian brown trout, revealed four major ph ylogenetic groups, three of which were found widely distributed within the southern Balkan region. The phylogeographical patterns revealed b y mtDNA represent one of the few cases where phylogenetic discontinuit y in a gene tree exists without obvious geographical localization with in a species' range and has most likely resulted from the differentiat ion of the major mtDNA clades during Messinian or early Pleistocene ti mes. Finally, the genetic relationships among the populations suggeste d by mtDNA were generally not in accordance with either allozyme or mo rphological data.