Comparative cytogenetics of Crocidura species: C. kegoensis, C. dracula and C.sibirica (Soricidae, Eulipotyphla).

Cytogenetic variation and chromosomal evolution in Palearctic white-toothed shrews (Crocidura) remain poorly understood, particularly within the Asian clade. Here, we provide the first cytogenetic characterization of Crocidura kegoensis and Crocidura dracula from Vietnam. All studied C. kegoensis individuals have stable karyotypes with 2n = 40 and FNa = 52 and are distinguished by large heterochromatic blocks on sex chromosomes. Different C. dracula specimens with equal FNa = 52 have 2n = 36-38 due to centromeric fusions. To enable comparative analysis within and beyond the genus, we generated a flow-sorted library for Crocidura sibirica and applied fluorescent in situ hybridization (FISH) to C. dracula metaphase chromosomes. Integrating our cytogenetic data with existing genetic evidence, we confirmed the presence of two distinct groups within the Asian clade of Palearctic shrews - northwestern and southeastern - that differ both genetically and karyologically. Using C. dracula as a focal taxon, we highlight ongoing, rapid speciation within the southeastern group and show that the extent level of chromosomal rearrangements in taxa correlates with their divergence time.