Morphological variation in the dentary of the Cave myotis (Myotis velifer) in the late Quaternary of Central Texas, USA

Moroz, Molly Jane
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The cave myotis, Myotis velifer, is a species of insectivorous bat distributed throughout the Southwestern US and Mexico. Fossils are known from several localities, including the well- known Hall’s Cave in Kerr County, TX, and multiple other caves in the Edward’s Plateau. Together, these caves capture faunal history from before the Last Glacial Maximum (18 kya) to the present, tracking significant warming and drying trends in local climate. Variation in body size across clines in the distribution of M. velifer has been observed in the present: bats in warmer, drier climates are smaller on average, while in cooler, wetter climates bats are larger. Previous studies capitalized on these modern trends and used linear measurements of fossils from Hall’s Cave as indicators of paleoclimate through time and found a trend of decreasing body size in M. velifer from the earliest occurrence to the present. Simple linear measurements of the skull may not capture changes in morphology, however, meaning that evolutionary change in skull morphology could have occurred without detection by previous researchers. Furthermore, recent studies of bat skulls showed the importance of morphology for enhancing fitness. In this study, I use geometric morphometrics to quantify changes in dentary shape of M. velifer through time. I show that dentary morphology and size differ across climate categories and that variation in morphology occurs in biologically significant anatomical features. By quantifying variation in dentary shape using geometric morphometrics, I can study the impacts on this species of past and future climate change.