Predator-prey interactions under climatic change: A mechanistic species distribution model

Xuezhen Ge and Cortland K. Griswold, Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, Jonathan A. Newman, Department of Biology, Wilfrid Laurier University, Waterloo, ON, Canada

Background/Question/Methods
Biotic interactions are an important determinant of species range shifts under climate change since they determine the species realized niche (sensu Hutchinson). However, species distribution models (SDMs) often neglect population dynamics and biotic interactions. Here, we conducted a case study by developing a mechanistic model of the cotton aphid (Aphis gossypii) and ladybird beetle (Harmonia dimidiata) predator-prey system. We derived a mechanistic model of the predator-prey dynamics with experimentally parameterized vital rates as functions of temperature. Using the historical (1970-2000) and future (2070-2100) projections of global temperatures, we calculated the annual aphid pressure (AAP; accumulation of daily aphid population abundance) in the presence and absence of the ladybird at the continent scale. We assessed the independent and interactive effects of climate change and predation on AAP.
Results/Conclusions
Our results indicate that the role of predation is as important as climate change in determining aphid population growth. Both effects vary spatially and reach the maximal magnitude in the low latitudes. Furthermore, climate change and predation do not generally combine additively. The results indicate that the relative importance of predation and climate differs between regions. Although their interaction per se rarely plays the dominant role, it alters the magnitude and/or the direction of the combined effects in most regions. This study highlights the direct and indirect effect of biotic interactions on focal species and suggests that ignoring biotic interactions in SDMs may result in misleading conclusions about the impacts of climate change.