16S rRNA gene polymorphism supports cryptic speciation within the lesser blind mole rat Nannospalax leucodon superspecies (Rodentia: Spalacidae)

Abstract

The role of intraspecific karyotype variability in reproductive isolation and speciation has been widely studied. Among the 26 genera of Palaearctic mammals, the blind mole rats genus Nannospalax has the highest karyotype variability with 74 chromosomal forms (CFs). Although these CFs have been described in detail, taxonomic effects of chromosomal rearrangements are still lacking, especially among 25 recorded CFs of European N. leucodon superspecies. As genetic discrepancies for most of them are missing, we analyze nucleotide sequence polymorphism of the mitochondrial 16S rRNA gene between eight N. leucodon CFs. Here we provide for the first time nucleotide sequence data for three CFs: monticola, montanoserbicus and syrmiensis using 40–57-year-old archived samples from our mammalian collection and thus demonstrate the usefulness of archived/museum samples as starting material for DNA analysis. The topology of the phylogenetic tree is congruent with the traditional taxonomic separation of recent blind mole rats with high support. Diversification of N. leucodon cluster into discrete subclusters—CFs—and the extent of evolutionary divergence among them are in accordance with previous findings of complete reproductive isolation between six CFs analyzed here. Additionally, the level of evolutionary divergence among six N. leucodon CFs resembles those recorded among clearly distinct Spalax species and four proposed species of N. ehrenbergi. These facts suggest that they could be cryptic species and bring attention to their conservation and natural resource protection.