The morphological, chromosomal and molecular illumination of the dramatic diversity of the stripe-backed shrews, Sorex cylindricauda species complex (Eulipotyphla: Soricidae)

Abstract The taxonomy of the stripe-backed shrew complex ( Sorex cylindricauda species group), distributed in mountains of western China, appears challenging due to remarkable variation in morphological traits and relatively recent times of diversification. According to classical points of view only two or three species of the stripe-backed shrews can be distinguished. However, previous molecular reconstructions revealed at least 14 genetic lineages including a number of undescribed cryptic species. In the current study we revise the taxonomic status of large-sized stripe-backed shrews occurring in high mountain areas in south Gansu, north-western Sichuan and western Qinghai that were previously treated as S. aff. cylindricauda or S. sinalis. The available molecular data place them in a separate species-level lineage of the stripe-backed shrew complex. Our morphological analysis indicate that shrews of this lineage are distinct from the two other large-sized Chinese species, S. cylindricauda and S. sinalis , based on both cranial and external traits. Therefore, we here describe it as a species new to science, the karyotype of which is characterized by 2n = 26 with an additional B chromosome and NFa = 44. Our molecular phylogenetic analysis demonstrates multiple instances of mitonuclear discordance among lineages within the S. cylindricauda complex, which is likely a result of mtDNA introgression, thus highlighting the important role of reticulation events in the evolution of the group.