Elucidating the effects of temperature and competition on native-invasive coexistence: A trait-based approach
Species invasions are one of the top environmental issues of the 21st century with negative impacts on natural ecosystems, agriculture, and human health. And yet, a mechanistic understanding of how the interplay between abiotic variation and biotic interactions influence invasion success is still lacking. Here we take a first step towards developing such a conceptual framework. We use a mathematical approach that uses delay differential equations to capture the developmental delays that characterize ectotherm life cycles. Importantly, this framework incorporates mechanistic descriptions of how temperature affects life history and interaction traits, and accommodates the variable developmental delays that arise due to seasonal and other forms of temperature variation. We implement our framework to investigate how the joint effects of temperature and competition influence invasion success in ectotherm species.
We find that amplitude of seasonal temperature fluctuations plays an overriding role in native-invasive coexistence and population dynamics. When fluctuations are small in magnitude, as in tropical climates, temperature variation allows the coexistence of species that otherwise exclude each other. When fluctuations are large in magnitude, as in temperate climates, dynamics become increasingly complex, eventually leading to the extinction of the species whose life history traits are more strongly influenced by temperature variation. A potential explanation for the increased complexity in dynamics is that species cannot respond sufficiently fast to large intra-annual changes in temperature, changes which are greater when annual fluctuations are larger in magnitude. This lag in response adds to the existing time lags due to developmental delays and delays in the operation of negative feedback arising from competition. This work thus provides for a greater mechanistic understanding of how the interplay between abiotic variation and biotic interactions influences native-invasive interactions.