ABSTRACT
Sympatric speciation was studied in two sister species of cottoid fish from Lake Baikal (East Siberia): big golomyanka or Big Baikal oilfish (Comephorus baicalensis Pallas, 1776) and small golomyanka or Little Baikal oilfish (C. dybowski Korotneff, 1905). Analysis of nucleotide sequences of mitochondrial cytochrome b gene showed that the Little Baikal oilfish (LBO) formed a single population in the lake, whereas the Big Baikal oilfish (BBO) was divided into two genetic groups - BBOI and BBOII, which were not separated geographically. Phylogenetic analysis showed that BBO is a more ancient species than LBO and that the paraphyletic origin of LBO is from the BBO genetic lineage within the genus Comephorus. Population-genetic structure and phylogenetic relationships between the two golomyanka species are considered to be a consequence of paleoenvironmental events that took place in the Baikal region during the past hundreds of thousand years.
