Trabecular bone is remodeled throughout an animal’s life in response to its mechanical environment, but like other skeletal anatomy, it is also subject to evolutionary influences. Yet the relative strengths of factors that affect trabecular bone architecture are little studied. We studied these factors across the Philippine endemic murine rodent clade Chrotomyini (earthworm mice). These mammals have robustly established phylogenetic relationships, exhibit a range of well-documented substrate-use types, and have a body size range spanning several hundred grams, making them ideal for a tractable study of extrinsic and intrinsic influences on trabecular bone morphology.

We found slight differences in vertebral trabecular bone among substrate-use categories, with more divergent characteristics in more ecologically specialized taxa. This suggests that mechanical environment must be relatively extreme to have an effect on trabecular bone morphology in small mammals. We also recovered allometry patterns that imply that selective pressures on bone may differ between small and large mammals. Finally, we found high intrataxonomic variation in trabecular bone morphology, but it is not clearly related to any variable we measured, and is possibly a normal manifestation of bone plasticity. Future studies should address how this plasticity affects biomechanical properties and performance of the skeleton.

Scans of murine vertebral columns (museum specimens sourced from the Field Museum of Natural History) were collected using a GE phoenix v|tome|x µCT scanner. Spherical VOIs were chosen and segmented in ORS Dragonfly 2021. Trabecular bone morphological data were collected from medullary cavity VOIs using Dragonfly and BoneJ. See publication Methods section for additional details.