BUILDING ECOMETRIC MODELS USING SMALL MAMMAL HYPSODONTY TO OBSERVE NOVEL TRAIT-ENVIRONMENT RELATIONSHIPS THROUGH TIME IN AFRICA

Ecometric analyses examine the relationships between functional traits and the environment at the community level. Traits used in these studies directly influence how an organism interacts with its environment. Previous studies using ecometrics have explored relationships between hypsodonty (tooth crown height) and precipitation. Many studies have analyzed this in large mammals. However, recent work found that hypsodonty in North American small mammal communities is correlated with mean annual temperature and annual precipitation. Here, we examined community-level hypsodonty of African Glires to test if the same relationship exists across geographic space. Africa’s rich biodiversity is of interest as Africa is expected to experience warmer and dryer climates in the near future. To investigate this trait-environment relationship in Africa, categorical hypsodonty values (brachydont, mesodont, and hypsodont) were gathered from the literature for 91 modern taxa. Equidistant 50-km points were used to generate community lists by sampling IUCN range maps across Africa. There was a stronger linear correlation between small mammal community-level hypsodonty and mean annual temperature (r=0.54, p<.001) than annual precipitation (r=0.14, p<.001). However, both relationships were weaker than expected based on North American mean annual temperature (r=0.86) and annual precipitation (r=0.66) correlations. We next constructed novel ecometric spaces to describe the relationship between hypsodonty and temperature. Using maximum-likelihood estimation methods, we determine that the trait-based estimates of temperature were, on average, 10°C warmer than the observed temperature values. To explore this relationship through time, we placed 25 well-sampled fossil localities from East Africa into our ecometric spaces based on their trait composition. Ten sites are non-analog communities and occupy trait space not represented by modern communities, making temperature estimates not possible. Half of these ten communities are Pleistocene in age and have higher mean hypsodonty values than are found in modern African communities. Fossil sites can help us understand how communities are shifting in trait space and in response to environmental change by revealing the direction and magnitude of change over time.