The northernmost blind beauty rediscovered: The identity and cryptic diversity of the troglobiotic millipede Typhloiulus polypodus (Loksa, 1960) (Diplopoda, Julidae) from caves of the Western Carpathians

European blind forms of millipedes in the family Julidae constitute a taxonomically diverse ecological group of mostly cavernicolous species inhabiting primarily the Balkan Peninsula. Their northernmost endemic populations are confined to a few caves in two neighbouring karst areas in the Western Carpathians of Central Europe. The first study of these Carpathian millipedes focused on the description of Allotyphloiulus polypodus Loksa, 1960 from the Bükk Mountains, which was later transferred to the genus Typhloiulus Latzel, 1884. For more than half a century, the species was known only from its original description, as the type specimens were considered lost. We collected specimens of this blind and endemic millipede for a molecular study during long-term biospeleological research in caves of the Slovak and Aggtelek Karst and, more recently, also in the Bükk Mountains, two neighbouring karst areas with distinct geological histories. DNA barcoding based on three molecular markers (COI, 16S, and 28S rDNA) provided the first information on the population genetics and phylogeny of this millipede. We found that the populations of these two adjacent karst regions were significantly genetically different, even though morphological differences have not yet been observed. Thus, Typhloiulus polypodus could represent a complex of two cryptic lineages. Phylogenetic relationships along intra- and interpopulation genetic variability were assessed. The results suggest that the studied Carpathian blind Julidae are less closely related to Typhloiulus Latzel, 1884 and the tribe Typhloiulini Verhoeff, 1930 than to the phylogenetic line represented by the genus Xestoiulus Verhoeff, 1893 (Leptoiulini Lohmander, 1936) or some members of the tribe Julini Leach, 1814, which has comprised only epigeic, non-eyeless representatives. This conclusion is preliminarily supported by the structure of secondary sexual characters. Finally, we discuss negative impacts threatening the local populations in show caves.