Biotic and abiotic factors are increasingly acknowledged to synergistically shape broad-scale species distributions. However, the relative importance of biotic and abiotic factors in predicting species distributions is unclear. In particular, biotic factors, such as predation and vegetation types, including those resulting from anthropogenic land-use change, are underrepresented in species distribution modeling, but could improve model predictions. Our goal was to understand the contribution of biotic and abiotic factors in predicting population density of an invasive large mammal with a global distribution. To evaluate our research objectives, we used the wild pig (Sus scrofa) as our focal species, which is one of the most destructive invasive species globally and is currently undergoing an unprecedented global range expansion. Using generalized linear models and model selection techniques, we used 129 estimates of wild pig population density from five continents to (1) evaluate the relative importance, magnitude, and direction of biotic (i.e., vegetation and predation) and abiotic (i.e., climate) factors in predicting population density and (2) create a predictive map of wild pig population density across the world.
Results/Conclusions
Incorporating diverse biotic factors, including those resulting from human land-use change, into species distribution modeling substantially improved model fit and predictions. Population density of wild pigs was driven by both biotic and abiotic factors, including potential evapotranspiration, large carnivore richness, precipitation during the wet and dry seasons, unvegetated area, and agriculture. The predictive map of population density revealed wide-ranging potential for an invasive large mammal to expand its distribution across all continents. This information can be used to proactively create conservation/management plans to control the spread of this invasive species. Our study demonstrates that the ongoing paradigm shift, which recognizes that both biotic and abiotic factors shape species distributions across broad scales, can be advanced by incorporating diverse biotic factors, including predation and human land-use change.