Abstract: Geometric morphometrics has been applied as a hot method for biological morphology research in recent years. In this study, geometric morphometrics was used to discuss the taxonomical similarities towards an exotic squirrel species (Callosciurus sp.) introduced separately into France, Belgium and Italy, by analyzing the mandibular shape. The results showed allometry effect can be found with statistical significance throughout all introduced populations, shape variations individually happened at coronoid process, angular process, masseteric ridge, and mental foramen of mandible, while among populations, shape varied largely at angular process; discriminant function analysis indicated the mandibular shapes of three introduced populations significantly differed, in which the French exotic population was more far from the other two, and Belgian and Italian populations were more closer to each other, so, we can deduce the exotic squirrels introduced into Belgium and Italy may belong to same species or origin, and the French introduced squirrel belongs to different one. And, the variations in mandibular shape among them may result from the respective ecological adaptation in different geographic regions. The subtle shape variation and taxonomical differences were investigated and visualized by means of geometric morphormetrics in this paper, which could be useful to taxonomically classify the exotic species and explore the introduced origin, and be referenced for biological morphology of invasive creatures.

Key words: Callosciurus, invasive species, geographical separate populations, mandibular shape, geometric morphometrics