One of the biggest questions that ecology asks is, how can so many different kinds of species coexist? Species interact with each other in many different ways. Some species compete for resources like food or places to live, some eat or parasitize others, some need other species in order to survive. Given all of these relationships, how do we explain, or even better predict, which species will be able to live with each other long-term (i.e. stably coexist)? This question is particularly important today, as global changes are altering which species are encountering each other. Ecologists have devised several theories to address the question of how species coexist. For example, species that compete for food may coexist by eating different types of food when they co-occur. Or, species may be better at acquiring food in different types of environments, and so may coexist by using different microhabitats. If species differ in traits that allow them to use resources or habitats in different ways, then trait differences can be used to predict if and how species can coexist. Whether trait variation predicts coexistence in consistent ways across all types of communities is a potentially powerful hypothesis that if true would allow researchers to predict how communities will change over time in response to environmental change. In principle, this hypothesis should apply across the tree of life. However, key aspects of the underlying theory have only been tested in a handful of study systems, mainly plants and microorganisms. As a result, the generality of these ideas and therefore their full impact remains untested in animal communities. This research will integrate morphology and ecology to test whether these ideas can apply to a lizard community. This research will contribute to broadening participation in science by providing research training to undergraduate students from the University of Hawaii, one of the most diverse college campuses in the country.
The research strategy is to 1) measure traits, 2) generate predictions for experimental outcomes based on trait differences and hypothesized coexistence mechanisms, and 3) test predictions using a mesocosm experiment. The study species are two anoles (Anolis carolinensis, A. sagrei), and a day gecko (Phelsuma laticauda), all of which are non-native to Hawaii. Lizards will be introduced to experimental enclosures with two different habitat treatments. The degree to which prey are differentially depleted by each species will be measured in the two habitats as a proxy for R*, which is the minimum resource level that can support a population. This will allow for determination of the importance of resource partitioning vs. spatial heterogeneity in competitive ability. Monitoring of mortality due to predation in the different habitat types will indicate the potential role for spatial heterogeneity in predator susceptibility in driving coexistence. By distinguishing among these mechanisms and connecting them to traits this research will generate and test predictions regarding the outcome of species interactions in arboreal lizard communities specifically, and more generally provide a case study to guide future work testing coexistence theory in macrofauna.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
