Mandible shape variation in minks: Separating two highly similar species

Research output: Contribution to conferenceAbstract

Author(s)

Department/unit(s)

Conference

ConferenceAnatomical Society Winter Virtual Meeting
CountryUnited Kingdom
CityNewcastle
Conference date(s)6/01/218/01/21

Publication details

DateUnpublished - 2021
Original languageEnglish

Abstract

European and American minks (Mustela lutreola and Neovison vison, respectively) are very similar in their ecology, behavior and morphology. However, the American mink is a generalist predator and seems to adapt better to anthropogenic effects, allowing it to outcompete the European mink in areas where it has been introduced, threatening the survival of the native species.
To assess whether differences in the masticatory apparatus allow American mink to exploit a wider range of food items than European mink, we analyzed shape variation in the mandible of both species using 3D GMM. A set of 18 landmarks and 22 semilandmarks was digitized on each specimen and, after superimposition, shape variation was explored with Principal Component Analysis. Differences in size and shape between and within species were assessed with Procrustes ANOVA.
European minks were shown to have a relatively taller coronoid process and a deeper angular process, while American minks presented a slightly longer, markedly concave corpus, which accommodated relatively larger teeth. Additionally, the masseteric fossa extended anteriorly in American minks. Both mink species presented a similar trend of shape changes with increasing size: an anteriorly displaced coronoid process and masseteric fossa, an enlarged angular process, an upwardly shifted premaxilla, and a dorsoventrally wider ramus. Significant differences in both size and shape of the mandible were found between species, and also between sexes (both pooling species and within species).
Overall, differences in mandible shape between species suggest that each mink might be adapted to maximize bite force at different teeth. In European minks, the increased in-levers for the temporalis and the superficial masseter and decreased out-levers for the canines and incisors would suggest a stronger piercing bite. American minks, on the other hand, have an increased in-lever for the deep masseter and a shorter out-lever at the carnassial, suggesting a stronger shearing/crushing bite. The marked curvature of the ventral corpus under the carnassial reinforces this hypothesis, since it has also been described in bone-crushing carnivorans. This apparent differentiation, however, is hard to relate to their diets, since both species prey on similar animals.

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