Microtus californicus toothrow and molar .tps files

<p><b>Aim. </b>This study examines how climate shaped <i>Microtus californicus </i>(Rodentia: Arvicolinae) ecomorphology throughout the Quaternary. It tests three hypotheses: (1) climate corresponds with consistent shape variation in <i>M. californicus </i>dentition; (2) Quaternary warming and drying trends caused <i>M. californicus </i>morphotypes to predictably shift in range through time; (3) Quaternary warming and drying led to predictable changes in tooth morphological variation. Finally, we discuss how shifts in climate-linked morphological variation may affect the potential of <i>M. californicus </i>to react to future climate change.</p> <p><b>Location. </b>Western United States.</p> <p><b>Taxon.</b> <i>Microtus californicus</i> (Peale, 1848)</p> <p><b>Methods. </b>Geometric morphometrics and partial least squares (PLS) analyses were used to discern how climate contributes to consistent variation in the shapes of the <i>M. californicus </i>lower first molar (m1), validated for the full toothrow. We further corroborate this relationship, reconstructing precipitation at fossil localities using m1 morphology and comparing those values to paleoclimate-model-derived precipitations. Disparity analyses and a MANOVA were performed to examine changes in variation and whether a shift in tooth shape occurred through time.</p> <p><b>Results. </b><i>M. californicus </i>m1 and toothrow shapes are narrower and more curved in cooler, wetter climates. Morphology-based paleoclimate reconstructions align with model-based paleoclimate estimations. When time averaging is accounted for, <i>M. californicus</i> demonstrates a 12% reduction in variation from fossil to present-day specimens, and these changes in tooth shape correspond with climate-related morphotypes.</p> <p><b>Main conclusions. </b>As California became drier and hotter since the late Pleistocene, <i>M. californicus </i>dental morphology generally tracked these changes by adapting to the consumption of rougher vegetation in drier environments. This resulted in the loss of some high-precipitation morphotypes, indicating that ecomorphology, often observed at the species and community levels, translates to intraspecific variation and dynamically changes in response to changing climates. The loss of climate-linked morphological variation since the late Pleistocene may limit the ability of <i>M. californicus </i>to respond to future changes in climate. These findings portend that other species may have experienced similar losses in adaptability.</p>