Investigation of nuclear and mitochondrial DNA polymorphism in closely related species of endemic Baikal sponges

In order to investigate the phylogenetic relationships among endemic Baikal sponges of the family Lubomirskiidae and to clarify their taxonomy, the sequence variation at the silicatein-encoding gene and the mtDNA intergenic region was examined. Phylogenetic analysis of the silicatein α1 gene exonic regions in six freshwater sponge species revealed considerable interspecific variability of this region. The analysis performed did not support the monophyly of the genera Lubomirskia and Baikalospongia. The mtDNA region between the COX2 and ATP6 genes was examined in five species from the Lubomirskiidae family, including multiple samples for analyzing intraspecific variations. According to the data obtained, the genus Baikalospongia was paraphyletic with respect to Lubomirskia, while B. bacilifera and B. recta did not form monophyletic groups. Molecular data indicate that taxonomy of Lubomirskiidae should be revised. It was demonstrated that, in endemic Baikal sponges, the accelerated evolution was accompanied by an increase in the length of the non-coding regions in both mitochondrial and nuclear genes.