How do two species coexist when each has a negative impact on the other? When a new species invades a habitat, how can we predict whether it will coexist with the native species, drive one or more of them extinct, or be driven to extinction itself by the natives? This research will investigate whether coexistence is an evolved property of species interactions. This will happen if species that could not coexist on first contact can act as agents of natural selection on each other's features in a way that enables them to evolve rapidly to coexist. Understanding when and how this evolution occurs can have a profound effect on our ability to predict the results of invasions, species re-stocking, and habitat alteration on biodiversity. This research will engage undergraduate researchers, as well as engaging the public with an outreach website.
This research focuses on one of the most challenging of species interactions, which occurs when the adults of two species compete with each other for food but each preys on juveniles of the other. This research will examine how Hart's killifish and Trinidadian guppies, which interact in this manner, somehow coexist in higher elevation streams in Trinidad. Typically, guppies encounter killifish when guppies invade locations that have held only killifish. This research exploits the fact that comparisons can be made among killifish populations that coexist with guppies and populations that have never encountered guppies, along with comparisons between guppy populations that have not invaded killifish-only locations, populations that have been introduced into those locations in recent experiments, and populations that have coexisted with killifish for decades. The work includes experiments in artificial streams that mix and match these populations to examine how fitness of each species depends on the combinations of its own genetic background and that of the other species. It also includes experiments in natural pools that remove one species to measure its net effect on the other. The researchers will also be documenting the fates of guppies and killifish in experimental introductions to assess how much evolution is actually occurring. There will also be laboratory experiments that pair individuals of different body sizes within and among species to understand how competition and predation depend on relative body sizes of interacting individuals. Finally, the research will synthesize these results with computational models that describe the ecological and evolutionary trajectories, which can be used as tools for understanding the fate of biodiversity in a variety of contexts.
