Integrative systematics of large-bodied blind mole rats (Rodentia: Spalacidae: Spalax) with description of Spalax lyapunovae sp. nov. from the North Caucasus

Abstract The systematics of blind mole rats (Spalacinae), a group of highly specialized subterranean rodents, remain a subject of debate. Within the genus Spalax , the greater blind mole rat ( Spalax microphthalmus ) is distinguished by its unique diploid chromosome number (2n = 60 versus 2n = 62 in others) and the most extensive geographic range. However, its intraspecific variation has been insufficiently studied. Previous finding of specimens with 2n = 62 in the North Caucasus were attributed to chromosomal polymorphism within S. microphthalmus . In this study, we conducted a comprehensive analysis of morphometric, morphological, molecular, and chromosomal variation across the entire range of S. microphthalmus , integrated with a comparative analysis of the genus Spalax . Our results demonstrate that the North Caucasian populations (2n = 62) exhibit consistent species-level differences in molecular genetics (from 8% to 12% divergence in cyt b ), karyotype, and cranial morphology, distinguishing them from S. microphthalmus and all other congeners. This lineage also possesses a unique combination of morphological traits, including features that bring it closer to the hypothetical common ancestor of all modern Spalax species. Based on this integrative evidence, we describe this lineage as a new species: Spalax lyapunovae sp. nov ., increasing the number of extant Spalax species to nine. This newly recognized species, endemic to the central North Caucasus, requires further ecological and distributional studies. Given its presumably limited range, an urgent assessment of its conservation status is warranted.