I examined the potential impact of climate change on species distributions using a model that included both abiotic and biotic factors. Because closely related species coexist with congeners through niche partitioning, understanding how species partition themselves under current climate conditions will improve our ability to predict their response to climate change. When species overlap, competitive and thermoregulatory ability play important roles in shaping species distributions.

Burying beetles (Coleoptera: Silphidae: Nicrophorus) are known for their large body size, strong flight, and use of vertebrate carcasses for reproduction. In a study of three sympatric burying beetle species (N. investigator, N. defodiens, and N. guttula) in the Rocky Mountains of Colorado, I examined habitat and seasonal niche partitioning through stratified field surveys, trapping at 29 sites over a 500 km² area. I also measured the outcome of competition for carcasses and thermoregulatory ability during flight. The results from field surveys were used to drive a maximum entropy (Maxent) model for predicting current habitat suitability across the study area (PresModel). Results were then projected onto future climate scenarios that increased temperature 2, 4 or 6°C and changed precipitation 90 or 110%. Separately, to account for changes in vegetation, vegetation type was first modeled under the climate scenarios and used as input into the Nicrophorus distribution models (VegModel).  
Results/Conclusions

The distribution data indicate that N. investigator is most abundant and a habitat generalist. N. defodiens is relatively rare, preferring forested habitats. N. guttula preferred the drier, sagebrush habitat at the lower elevations  N. defodiens is active early in the season; N. investigator and N. guttula peak in late July. These results suggest niche partitioning based on season, moisture, and vegetation. Results from the competition study followed the observed size distribution among the three species, (N. investigator > N. defodiens > N. guttula). All three species raised their body temperature above operative temperature post-flight, but there was no significant difference in thermoregulatory ability. 

Habitat suitability models from Maxent had high AUC values (>0.87) and gave reasonable predictions for all three species. N. investigator and N. guttula habitat suitability is predicted to expand under the 90% precipitation climate models and contract under all other scenarios. Suitable habitat for N. defodiens is predicted to dramatically decrease under all but one scenario. Results from the VegModel predicted Nicrophorus suitable habitat to change in the same direction as PresModel, but in greater magnitude.