Geographic variation of craniodental morphology of the Eurasian otter (Lutra lutra) in East Asia

Craniodental morphology of the Eurasian otter (Lutra lutra) in the Korean Peninsula, Japanese islands and Kinmen Island (Taiwan) was studied using geometric morphometrics to identify the skull variations between the populations. Forty adult skulls were examined (29 specimens from the Korean Peninsula, six from Shikoku, Honshu and Hokkaido of Japan, and five from Kinmen Island). Images of the dorsal and ventral views of the skull and the right lateral view of the mandible were analyzed. Specimens from the Korean Peninsula were larger than those from the Japanese islands and Kinmen Island. However, no correlation was observed between the shape variations in the three populations and the centroid size of the skull. The Mann-Whitney U-test showed that relative warps (RWs) RW1, RW2 and RW4 of the dorsal view and RW2 of the ventral view of the skull differed significantly between the populations. Some craniodental differences between the populations were seen in the dorsal and ventral views of the skull, mostly at the snout and parietal regions. The MANOVA test revealed significant differences between the specimens from the Japanese islands and Korean Peninsula and between the specimens from the Korean Peninsula and Kinmen Island. RWs plots showed an overlap of all three populations. In conclusion, the comparisons of the three examined populations revealed significant differences in their craniodental morphology.