The utility of body size as a functional trait to link the past and present in a diverse reptile clade

Abstract

Understanding the relationships between functional traits and environment is increasingly important for assessing ecosystem health and forecasting biotic responses to future environmental change. Taxon-free analyses of functional traits (ecometrics) allow for testing the performance of such traits through time, utilizing both the fossil record and paleoenvironmental proxies. Here, we test the role of body size as a functional trait with respect to climate, using turtles as a model system. We examine the influence of mass-specific metabolic rate as a functional factor in the sorting of body size with environmental temperature and investigate the utility of community body size composition as an ecometric correlated to climate variables. We then apply our results to the fossil record of the Plio-Pleistocene Shungura Formation in Ethiopia. Results show that turtle body sizes scale with mass-specific metabolic rate for larger taxa, but not for the majority of species, indicating that metabolism is not a primary driver of size. Body size ecometrics have stronger predictive power at continental than at global scales, but without a single, dominant predictive functional relationship. Application of ecometrics to the Shungura fossil record suggests that turtle paleocommunity ecometrics coarsely track independent paleoclimate estimates at local scales. We hypothesize that both human disruption and biotic interactions limit the ecometric fit of size to climate in this clade. Nonetheless, examination of the consistency of trait–environment relationships through deep and shallow time provides a means for testing anthropogenic influences on ecosystems.

Challenges and opportunities in applying AI to evolutionary morphology

“…The related field of ecometrics is a taxon-free approach to quantifying the distribution of functional traits across space and time (Eronen et al, 2010). Ecometric correspondence between environmental and phenotypic data is used to develop transfer functions which can be used to reconstruct paleoenvironments or incorporate Species Distribution Modelling (SDM) to model future spatial distributions of phenotypes given predicted climatic scenarios (Parker et al, 2023;Vermillion et al, 2018). Existing work uses linear and maximum likelihood approaches to perform ecometric modelling.…”

“…Existing work uses linear and maximum likelihood approaches to perform ecometric modelling. These approaches have a limit of one or two climate inputs, normally limiting analyses to consider only annual precipitation and mean annual temperature (Parker et al, 2023). However, a Random Forest approach would enable the model to use any number of climatic variables.…”

The past as a lens for biodiversity conservation on a dynamically changing planet

“…Parker et al. ( 31 ) and Short et al. ( 32 ) examine how well community-level functional traits align with the environments where they are found as change occurs across space and through time.…”

“…Parker et al. ( 31 ) use a well-established physiological relationship between turtle body size and temperature to examine trait–environment patterns globally. To do this, they calculate the body sizes of turtle communities from every continent and compare them to anticipated body sizes based on physiological models.…”