Discordant phylogenies in the Sorex araneus group (Soricidae, Mammalia): Footprints of past reticulations?

In the present study, we reconstruct phylogenetic relationships within the chromosomally variable Sorex araneus species group based on 20 nuclear loci and the mitochondrial cyt b gene. In the species tree, Nearctic S. arcticus represents the earliest offshoot of the group followed by Holarctic S. tundrensis and Siberian S. daphaenodon. Five other species distributed mostly in Europe form a well-supported clade. Coding regions showed stronger phylogenetic signal than introns. The results suggest a high incidence of reticulation in the evolution of the group. The authentic mitochondrial lineage of the Iberian shrew S. granarius was found to be close phylogenetically to S. coronatus, which confirms that some populations of the Iberian shrew S. granarius were introgressed from S. araneus. Footprints of deeper reticulations are revealed for the first time, indicating the potential hybrid origin of the S. arcticus and S. coronatus lineages. Ancient hybridisations are hypothesised to be the source of discordance between molecular- and karyotype-based phylogenetic reconstructions.

Automated summary

In this study, the phylogenetic relationships within the chromosomally variable Sorex araneus species group were reconstructed using nuclear and mitochondrial genes. The results showed a complex evolutionary history with high incidence of reticulation and possible ancient hybridizations. The authentic mitochondrial lineage of the Iberian shrew S. granarius was found to be closely related to S. coronatus, indicating introgression from S. araneus. This study also revealed deeper reticulations for the first time, suggesting hybrid origins for the S. arcticus and S. coronatus lineages.