PS 11-126 - CANCELLED - Linking functional traits to competitive ability in a novel lizard assemblage

Abstract: Novel communities are increasingly formed due to anthropogenic effects, and predicting the long term structure of these communities is a pressing concern. If we understand the mechanisms linking functional traits to resource use then we can predict species overlap in resource use based on their traits. However, resource overlap is necessary, but insufficient, for competition to occur. R* theory provides a useful measure of competitive ability: for two species using one resource, the one that depletes the resource to the lowest concentration is the superior competitor. Here we used functional traits to predict which species in a novel lizard community should be the best competitors in different microhabitats, then tested these predictions by measuring prey depletion. Our study system is a novel community of introduced lizards to Hawaiʻi: anoles (green anoles, Anolis carolinensis, and brown anoles, Anolis sagrei) and day geckos (gold dust day geckos, Phelsuma laticauda). Previous work showed that day geckos and green anoles use similarly high perches, while brown anoles perch lower in the vegetation. In terms of functional traits, day geckos have better clinging ability than green anoles, and therefore we predicted that they should be superior competitors for prey in the vegetation. To test competitive ability in different microhabitats, we established monocultures of each of the three species in 10m x 10m experimental enclosures with controlled resource availability (n = 2 enclosures per species). We used 14 female and 7 male adults to initiate each population, and allowed the populations to grow for over one year. While lizard density and size distribution varied over time, total lizard biomass in each enclosure rapidly stabilized. Concurrent with lizard population growth, we monitored prey every two weeks using pan traps on the ground and in the vegetation. Patterns of prey depletion were consistent with predictions: brown anoles suppressed prey the most on the ground, day geckos suppressed prey most in the vegetation, and green anoles suppressed prey the least in both habitats. Consistent with these experimental results, field surveys show that green anoles are now the rarest of the three species on O’ahu, when prior to the introduction of the other two species they were widespread and abundant.