Genetic separation of gammarid (Eulimnogammarus cyaneus) populations by localized topographic changes in ancient Lake Baikal

Abstract

Individuals of the gammarid Eulimnogammarus cyaneus, a littoral species endemic to Lake Baikal, were collected at 11 localities along the southwest shore of that lake, and the population genetic structure was investigated by allozyme analysis of 21 gene loci. The populations were genetically separated (Nei's D = 0.0126) between the northern and southern localities divided by the outlet into a large drainage, the Angara River. The origin of the genetic separation was estimated by a molecular clock to be 60,000 years ago, which coincided with the geologically observed rise of that outlet as a barrier to gene flow during the 2nd half of the Late Pleistocene. The result suggests that intralacustrine speciation by localized topographic changes played a substantial role in the steady increase of indigenous species in ancient lakes.