Molecular phylogeny of Baikalian Lumbriculidae (Oligochaeta): evidence for recent explosive speciation

The phylogenetic relationships of the Lumbriculidae (Oligochaeta) of Lake Baikal (Siberia, Russia) were investigated with a data set of new mitochondrial COI gene sequences of 26 species, 25 of which belong to Baikalian fauna. Species of the most representative genera inhabiting the lake, Lamprodrilus Michaelsen, 1901, Agriodrilus Michaelsen, 1905, Teleuscolex Michaelsen, 1901, Stylodrilus Claperede, 1862, Styloscolex Michaelsen, 1901, and Rhynchelmis Hoffmeister, 1843, were included in the data set. The possibility of explosive speciation events was investigated in studying deviations of the observed rates of cladogenesis from a uniform one. In contrast, the monophyly of most genera was recovered, with the exception of Lamprodrilus and Rhynchelmis. The polyphyletic nature of Rhynchelmis gave support to the revalidation of the genus Pseudorhynchelmis suggested on morphological characters. The lack of phylogenetic signal in the Lamprodrilus-group was interpreted as evidence of explosive radiation of the genera of this group (Lamprodrilus, Agriodrilus, and Teleuscolex), 4 to 3 million years ago, and was put in the context of the Baikal Rift Zone history.