Intron-based phylogeny revealed a substrate role in the origin of the gastropod species flock from Lake Baikal

Abstract

A nuclear marker, an intron of ATP synthase α-subunit gene, used to determine phylogenetic relationships between 22 species of the family Baicaliidae (Caenogastropoda: Rissooidea) indicated two genetic groups of these gastropods in Lake Baikal. The obtained groups partially coincide with the clusters revealed by the mitochondrial COI gene and do not fully coincide with the modern taxonomy of the family. Thirteen species of the first group inhabit different sediments (silty sand, sand, stones, and rocks), eight out of the nine species from the second group are psammobionts. Both genetic groups include eurybathic and stenobathic species widely distributed in the North, Middle and Southern Basins of the lake, as well as species, whose habitats are limited to one or two basins. Phylogenetic analysis suggests that the main way of baicaliids speciation was the repeated occupation of the same habitats by different ancestral forms. Sculpture of the shells (ribs, carina and/or periostracal hairs/plates) also most likely appeared independently in each group due to similar adaptation.