Nested clade and phylogeographic analyses of the chub, Leuciscus cephalus (Teleostei, Cyprinidae), in Greece: Implications for Balkan Peninsula biogeography

Phylogenetic relationships among Greek populations of the chub, Leuciscus c ephalus, were investigated using 600 bp of the cytochrome b gene The aim of this study was to test the assumption that the main difference in ichthyol ogical composition between both sides of the Balkan Peninsula is directly l inked to differences in the dispersion mechanisms used by fish in order to extend their distribution range. Phylogenetic and nested clade analyses cle arly showed that populations in Greece are significantly differentiated. Gr eek populations were found to descend from three lineages in three geograph ical provinces: Western, Central, and Eastern Greece. The chub reached West ern Greece at the beginning of the Pleistocene and Eastern Greece during th e mid-Pleistocene. Chub dispersion occurred mainly by river confluence due to sea level lowering and river capture in Western Greece and sea dispersal with low-salinity conditions within the Aegean Sea in Eastern Greece. Howe ver, in Central Greece, the original mtDNA lineage has presumably been lost owing to a genetic introgression following a second invasion from the Danu be during the final stage of the last glaciation. This study provides new e lements for a better understanding of the composition of the contemporary i chthyofauna in Greece and highlights possible evolutionary mechanisms respo nsible for the high endemism rate in the Western Greek. biogeographic provi nce. (C) 1999 Academic Press.