Biotic and abiotic factors predicting the global distribution and population density of an invasive large mammal

Jesse S. Lewis,Ryan S. Miller,Chris L. Burdett,Miranda Gray,Matthew L. Farnsworth,David M. Theobald

doi:10.1038/srep44152

Abstract

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, including those resulting from anthropogenic land-use change, are underrepresented in species distribution modeling, but could improve model predictions. Using generalized linear models and model selection techniques, we used 129 estimates of population density of wild pigs (Sus scrofa) from 5 continents to evaluate the relative importance, magnitude, and direction of biotic and abiotic factors in predicting population density of an invasive large mammal with a global distribution. Incorporating diverse biotic factors, including agriculture, vegetation cover, and large carnivore richness, into species distribution modeling substantially improved model fit and predictions. Abiotic factors, including precipitation and potential evapotranspiration, were also important predictors. The predictive map of population density revealed wide-ranging potential for an invasive large mammal to expand its distribution globally. This information can be used to proactively create conservation/management plans to control future invasions. 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.

Highlights

Predation and symbioses, can be important determinants[15,17], but have received less attention[18]
Researchers have evaluated the effects of biotic interactions on geographic range limits[18], relatively few studies have evaluated how biotic factors influence population density across a species’ range[19,20], which can be more informative in understanding macro-ecological patterns[7,21]
Wild pigs are a model species to evaluate biotic and abiotic factors associated with population density because they exhibit a global distribution across six continents, are widely studied across much of their native and non-native ranges, and previous research has indicated that their population density was related to abiotic factors across a continental scale, it was ambiguous how biotic factors shape their abundance, warranting further study[42]

Summary

Introduction

Predation and symbioses, can be important determinants[15,17], but have received less attention[18]. Wild pigs are a model species to evaluate biotic and abiotic factors associated with population density because they exhibit a global distribution across six continents, are widely studied across much of their native and non-native (i.e., invasive or introduced) ranges, and previous research has indicated that their population density was related to abiotic factors across a continental scale, it was ambiguous how biotic factors shape their abundance, warranting further study[42] To address these ecological questions and understand the relative importance of biotic and abiotic factors in shaping the global distribution of a highly invasive mammal, we evaluated estimates of population density of wild pigs across diverse environments on five continents. Our results contribute novel insight into the relative roles of biotic and abiotic factors in shaping the distribution of species’ population densities across continental and global scales, relating to human-mediated land-use change, which can provide critical information to management and conservation strategies

Methods

Results

Conclusion