2018 ESA Annual Meeting (August 5 -- 10)

COS 58-8 - The mechanistic underpinnings of latitudinal directionality in ectotherm invasion success

Wednesday, August 8, 2018: 10:30 AM
356, New Orleans Ernest N. Morial Convention Center
Margaret Simon, Department of Biology, University of Florida, Gainesville, FL and Priyanga Amarasekare, Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA
Background/Question/Methods

Species invasions constitute a major threat to natural and human-altered communities. Many high-impact invaders are ectothermic: demography and the strength of interactions with native species are heavily influenced by the thermal environment. Because environmental temperature (mean and variance) changes predictably across latitude, we expect that thermal traits characteristic of ectotherms adapted to one latitude confer a disadvantage to the same species attempting to colonize and establish into a different latitude. Further, we expect the mismatch between thermal adaptation and novel environment to be asymmetrical between invaders moving up a latitudinal gradient versus down it. Indeed, such a pattern exists in the literature: lower-latitude ectotherms are more successful at invading higher-latitude communities than vice versa. Yet, we still have a poor understanding of the mechanisms by which thermal adaptation to a given latitude influences ectotherm species' colonization ability and interactions with native competitors in lower or higher latitudes. Here we present a trait-based, mathematical framework to investigate how temperature effects on native-exotic competition influence the ability of an invasive species from a given latitude to increase when rare and successfully establish into a community at a different latitude.

Results/Conclusions

Our model supports the the hypothesis that lower-latitude ectotherms are more successful at colonizing and establishing in higher-latitude communities. We find that characteristics of demography traits consistent with lower-latitude ectotherms (e.g., high thermal optimum of reproduction) allow such species to successfully colonize and establish among native species in higher-latitude habitats. Interestingly, these same trait characteristics allow lower-latitude species to exert strong competition on higher-latitude invaders, impeding their establishment into lower-latitude communities. Predictions of our framework provide for a mechanistic interpretation of the classical argument about latitudinal diversity gradients, i.e., species invading lower latitudes are hindered more by biotic interactions (competition with native species) than the harshness of the abiotic environment, while species invading higher latitudes are hindered more by the harshness of the abiotic environment than by biotic interactions. Our attempt to develop a mechanistic understanding of latitudinal variation in invasion success not only yields novel insights into the role of thermal adaptation in contributing to latitudinal diversity gradients, but also provides a conceptual basis for addressing important practical concerns regarding ectotherm invasion success in the face of climate warming and ongoing globalization.