Mariia N. Semerikova

Mitochondrial DNA is a powerful marker for reconstructing maternal lineages and phylogeographic history in wild species. The snow sheep (Ovis nivicola), a mountain ungulate endemic to Siberia and the Russian Far East, is characterized by strong geographic fragmentation and a complex taxonomic structure. A formal mitochondrial haplogroup classification system for the species has, however, been lacking. In this study, we sequenced and analyzed 257 complete mitochondrial genomes representing all major populations across the species’ range. Using phylogenetic reconstruction and diagnostic mutations (present in 100% of individuals within clades), we identified four major haplogroups (A–D) and multiple nested sub-haplogroups with clear geographic structuring. Divergence times were estimated using Bayesian analysis in BEAST 2.7.7 with a relaxed lognormal clock model, calibrated by the divergence between O. dalli and O. canadensis. The results showed that haplogroup A is almost exclusive to Kamchatka, haplogroup B is predominant in northern populations, haplogroup C is the most widespread and diverse across the species range, and haplogroup D is largely restricted to the Verkhoyansk region. The mitochondrial data largely support traditional subspecies taxonomy but reveal mitochondrial polyphyly in some subspecies, particularly O. n. lydekkeri and O. n. koriakorum. This study provides the first comprehensive mitochondrial haplogroup system for snow sheep and shows that the observed mitochondrial phylogeographic patterns are consistent with an important influence of Pleistocene glacial cycles and prolonged geographic isolation on its current genetic structure. These findings offer important insights for conservation management and for understanding the evolutionary history of wild sheep in Northeast Asia.

The snow sheep ( Ovis nivicola ) is a wild mountain artiodactyl inhabiting the highlands of northeastern Siberia and the Russian Far East. Despite its ecological and conservation importance, the intraspecific taxonomy of this species has long remained controversial due to its broad distribution, morphological variability and limited available material. In this study, we performed a comprehensive genome‐wide single nucleotide polymorphism (SNP) analysis, encompassing all major described populations to clarify the evolutionary relationships and taxonomic structure of snow sheep. A total of 337 individuals from 15 populations were genotyped using Illumina OvineSNP50 and OvineHD 600 K BeadChips, with 1032 autosomal SNPs retained after quality filtering. Population structure analyses revealed eight major genetic clusters largely corresponding to geographic regions: Kamchatkan, Koryak, Okhotsk/Chukotka, Yakutian (Moma Range), Yakutian (Verkhoyansk Range), Yablonov, Kharaulakh and Putorana. Pairwise F _ST values confirmed substantial differentiation among most populations. Using f ₃ ‐statistics, two significant admixture events were identified, one involving the Orulgan and another the northern Kamchatka populations. Based on the integrated genomic and historical evidence, our results support the taxonomic recognition of the Kamchatkan ( O. n. nivicola ), Putorana ( O. n. borealis ), Okhotsk ( O. n. alleni ), Koryak ( O. n. koriakorum ), Yakutian ( O. n. lydekkeri ), and Stanovoy/Yablonov ( O. n. potanini ) subspecies, and propose recognition of the Kharaulakh snow sheep as a new subspecies, O. n. ernsti . The Kodar population, characterized by extremely low heterozygosity, requires further sampling to resolve its taxonomic position. These findings provide the first genome‐wide framework for understanding the evolutionary history of snow sheep and establish a genetic basis for future conservation management.

The intraspecific taxonomy of snow sheep (Ovis nivicola) is one of the most controversial issues in Caprinae systematics. Although eight subspecies have been described using morphological traits, the validity of several taxa, particularly those in the eastern part of their geographical range, remains disputed. We investigated the phylogenetic relationships and genetic diversity of snow sheep in the Chukotka Autonomous Okrug using genome-wide single-nucleotide polymorphism (SNP) data (935 loci after filtering) and complete mitochondrial genomes from 57 individuals collected across the Russian Far East (Chukotka Autonomous Okrug, Kamchatka Krai, Magadan Oblast, and Republic of Sakha (Yakutia)). Post SNP-genotyping nuclear genomic studies using principal component analysis (PCA), ADMIXTURE, pairwise F_ST and Neighbor-Net revealed two clearly differentiated groups within Chukotka. One included individuals from the Koryak Mountains that are genetically indistinguishable from the Koryak subspecies (O. n. koriakorum) of northern Kamchatka. The other one encompassed individuals from the Anadyr Plateau and the Chukotka Mountains cluster with the Okhotsk subspecies (O. n. alleni) of the Kolyma Mountains. Bayesian phylogeny of complete mitochondrial genomes fully corroborated the nuclear results: Koryak Mountains samples formed a monophyletic clade, while Anadyr–Chukotka samples grouped with Kolyma Mountains individuals. Genetic diversity indices (_UH_E, A_R, F_IS) in both Chukotka groups were comparable to other studied populations and showed no signs of inbreeding depression. Our results provide important insights and can be used to develop science-based strategies for preserving the population-genetic diversity of snow sheep.

The Russian Arctic supports wild sympatric ruminants and their data-deficient helminths. In this study, we: (1) collected fecal samples of wild and semiwild reindeer (Rangifer tarandus), muskoxen (Ovibos moschatus), and snow sheep (Ovis nivicola) across Palearctic North territories: Arkhangelsk Oblast (including Novaya Zemlya archipelago), Karelia and Sakha Republics, Kola, Yamal, Taimyr, and Chukotka Peninsulas, Bering, Svalbard, and Wrangel Islands; (2) conducted a coprological survey (noninvasive life-time method preferable for protected animals) to obtain eggs and larvae of helminths inhabiting digestive, respiratory, nervous, and muscular systems; (3) identified helminths according to their morphology and DNA sequences; (4) estimated parasite load per host; (5) analyzed our findings. Varestrongylus eleguneniensis (in reindeer) was reported for the Palearctic for the first time, while Orthostrongylus sp. was reported both for R. tarandus and for the Palearctic for the first time. Capillarid-type eggs were reported for snow sheep for the first time. The question of the role of wild Arctic ruminants as vectors for rotifers was raised.