Fossil bats’ (Myotis velifer) jaw morphology changes through time and with climate change in Hall’s Cave, Texas

Date

2020-01-04

Authors

Kemp, Melissa
Moroz, Molly

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Publisher

Society for Integrative and Comparative Biology

Abstract

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. Hall’s Cave represents a continuous fossil record from 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 M. velifer’s distribution 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 in this previous study; furthermore, recent studies of bat skulls have shown the importance of morphology for enhancing fitness. In this study, we use geometric morphometrics to quantify changes in M. velifer mandible shape through time in Hall’s Cave. Preliminary data shows that mandible morphology differs between the oldest and youngest M. velifer fossils in Hall’s Cave and that variation is greatest in the temporomandibular joint, which may have implications for changing bite force through time. By quantifying variation in mandible shape using geometric morphometrics, we can study the impacts of past and future climate change on this species.

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