How Mammals Move: Locomotory Function in the Soricidae

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The Challenge: The postcranial skeletons of mammals exhibit tremendous variation in form that partly relates to phylogeny (who a particular species is related to) and partly to locomotory function (how that species moves through its environment). Understanding the contributions of these two factors is important because phylogenetic characters assist in working out evolutionary relationships, whereas locomotory adaptations help to determine how a species interacts with its environment. 

The Science: There is surprising diversity in the postcranial skeletons of shrews (Soricidae), and, with the assistance of numerous students, I have been investigating locomotory functions in North American and African shrews, initially as they related to adaptations for moving at the soil surface vs. those for digging.  We have discovered that these are not discrete states, but that skeletons of various species present a continuum of grades of adaptation. By mapping adaptations for digging on molecular phylogenies, we found that similar adaptations for digging have evolved within the family numerous times. 

The Future: The database for digging shrews is expanding to include Asian and additional North American taxa. Research is now also focusing on adaptations for other modes of locomotion in shrews, such as swimming and climbing.