Population genetic structure of the endemic sponge Lubomirskia baikalensis in Lake Baikal in the light of mass disease and mortality events

Abstract

The study of the state of Baikal endemic sponge populations is of great interest because of the occurrence of mass mortalities and disease in recent decades. To identify possible signs of species vulnerability to extinction, it is crucial to develop appropriate genetic markers that help developing measures for conservation. In this paper, we describe the population genetic structure of the Baikal endemic sponge Lubomirskia baikalensis examined with the set of microsatellite markers we developed. We analysed 251 samples from eight locations that cover all three basins of Lake Baikal. A genetic subdivision into three clusters was revealed. Such a structure can be explained mainly by the low ability of larvae to disperse. Despite the presence of dead and diseased individuals in all studied locations, all populations were in Hardy–Weinberg equilibrium and no bottleneck effect was found at all. This is the first time that a genetic connectivity study has been performed for L. baikalensis, a species endemic of Lake Baikal. Reconstruction of the changes in the effective population size agrees with the results obtained during drill sample analysis and it demonstrates that the effective population size was 55.5 times lower about 24,000 years ago, which indicates that apparently there is no threat of extinction of the Baikal endemic sponges at present.