Phylogeography of earthworms from high latitudes of Eurasia

Abstract

Earthworms are an important component of soil fauna even in high latitudes, in the taiga and tundra biomes. It is yet unclear if earthworm populations from these regions are autochtonous or recent invaders. We collected earthworms from approximately from 64° to 73°N from the Kola Peninsula to Chukotka and genotyped it using the COI gene. We found Dendrobaena octaedra, Lumbricus rubellus, and Eisenia nordenskioldi nordenskioldi. Within E. n. nordenskioldi, two cryptic phylogenetic lineages were detected, namely lineages 1 and 9 that were characterized in our previous studies. The western part (from the Kola Peninsula to the Taimyr Peninsula) contained D. octaedra, L. rubellus and both lineages of E. n. nordenskioldi; their COI sequences were closely related to those from very remote (up to several thousand km) populations. On the contrary, in the east (from the basins of the Anabar River to the Chukotka Peninsula) we found solely E. n. nordenskioldi belonging mostly to lineage 9 and its haplotype groups from various parts of this region differed significantly, indicating long-term divergence. Thus, our data suggests that earthworms recolonized northwestern Eurasia in the Holocene, while the climate in its eastern part was sufficient for earthworm survival even during glaciation maximums.