What jaws and teeth reveal: Tracing fine-scale ecological adaptation in two Cypriot mice.

Anatomical structures can capture evolutionary history as well as short-term ecological adjustments, but distinguishing these signals remains challenging at fine spatial and temporal scales. In murine rodents, representing one of the most diverse mammalian radiations, mandibular and dental morphology provide powerful markers of both phylogenetic divergence and feeding-related adaptation. This study investigates these signatures in two mouse species co-occurring on the island of Cyprus: the introduced house mouse Mus musculus domesticus and the endemic Mus cypriacus. Although morphologically similar and occasionally syntopic, the two species differ in habitat use and dietary strategies, ranging from anthropogenic resources in M. m. domesticus to a more natural and diversified trophic niche in M. cypriacus. Using 3D geometric morphometrics, shape variation of mandibles and molars was quantified, allowing to identify interspecific differences, allometric patterns, and age-related trajectories of dental wear. The morphometric descriptors were questioned regarding their respective ability to trace phylogenetic divergence, ecological specialization, and ontogenetic dynamics. The results highlight how subtle morphological descriptors can reveal fine-scale ecological processes and species-specific adaptive pathways.