Bite force and evolutionary studies in phyllostomid bats: a meta‐analysis and validation

Bite force measurements are relevant to the functional performance and provide insights about ecology and evolution of vertebrates. Bats are a good model system for ecomorphological studies of bite force because communities are species rich and the animals are easy to capture and handle. Investigators are careful with standardization within studies to ensure internal validity, but differences in methods for measuring bite forces in live animals could decrease external validity (generalization) of results. We assembled published and new estimates of in vivo bite forces, where the same species were measured by different investigators using different methods in different locations, to perform a meta-analysis, assess the statistical heterogeneity of results and examine possible causes of among-study differences. We also compared the combined measurements of in vivo bite force to estimated bite forces from skull pictures of museum specimens (dry skull model) to check for biases and validate the estimates. The results showed that in vivo bite force measurements were statistically heterogeneous, particularly for species with four or more published estimates. Body mass measurements were also heterogeneous but size could not explain the experimental differences in bite force within species. Type of sensor used also did not explain the among-study variation. The random differences among studies did not, however, compromise external validity, because at an evolutionary scale, variation within species (including that due to heterogeneity) is less than 10% of variation among species. Therefore, the biological interpretation of results is not affected by experimental heterogeneity. Estimates of bite force using museum specimens were validated as unbiased predictors of in vivo bite forces via regression, and the macroevolutionary pattern of variation among dietary specializations was consistent among estimates, suggesting reasonable external validity for both model and in vivo measurements of bite force at an evolutionary scale.