Insular variation of the craniodental morphology in the Siberian weasel Mustela sibirica.

We compared craniodental morphology among 5 populations of the Siberian weasel Mustela sibirica including 2 insular ones (Tsushima and Taiwan). Skulls of the insular individuals tended to be smaller than those of continental ones. Shape differences were also detected, but not so pronounced. Considering these results, the Taiwan population should be regarded as a distinct subspecies M. s. taivana from the mainland ones. The Tsushima population may also possibly be a distinct subspecies from the mainland ones, but more detailed studies using a larger number of specimens are needed for a conclusion. The introduced population in Honshu is also differentiated from the source population. This suggests a high morphological plasticity in M. sibirica.