Genetic Structure and Diversity of Eurasian Otter (Lutra lutra) in Northern Eurasia and Caucasus: Are There Any Differences Between the Two Subspecies?

The Eurasian otter (Lutra lutra) is a widespread semiaquatic carnivorous mammal in Eurasia. The nominate subspecies (L. l. lutra) occupies vast areas between Western Europe and the Russian Far East, but its phylogeography and genetic diversity are still unclear across Northern Eurasia. Another subspecies, L. l. meridionalis, located in the Caucasus mountains, is morphologically almost identical to L. l. lutra but needs genetic revision. We compared the genetic diversity of Eurasian otters from Russia and Armenia using a mtDNA fragment (820 bp) and 20 autosomal microsatellite loci (N = 117). A total of 32 haplotypes were observed with 17 novel haplotypes. The MtDNA median-joining network was mostly star-shaped with a branch of haplotypes from Far Eastern Russian otters. Both mtDNA analysis and Bayesian clustering of microsatellite data indicated that Far Eastern otters are more genetically differentiated than European and Siberian otters (Φst = 0.565 and 0.467; Rst = 0.306 and 0.256), as well as Caucasian otters (L. l. meridionalis) from Russia and Armenia (Φst = 0.515, Rst = 0.253). Haplotype and nucleotide diversities of Far Eastern otters are also the highest between sample groups (H = 0.882, π = 0.003) and, of Caucasian otters, the lowest (H = 0.464, π = 0.001). Our results suggest Caucasian otters are more similar to the otters from European Russia than to the other groups (but with lower genetic diversity) and lack the genetic variability typical to different subspecies. On the contrary, otters from the Russian Far East are more genetically differentiated, have higher genetic diversity than otters from Europe, and likely belong to another genetic lineage.