Non-native species are considered invasive when they grow and spread rapidly in their new location. A single species invasion may affect food webs (the structural links of predators and prey) and ultimately the flow of energy and cycling of nutrients from vegetation producers through animal consumers. When multiple species invade an ecosystem, these effects may be magnified. On isolated islands, such as the Hawaiian Islands where numerous species are both unique and have limited geographic range, the probability of extinction in the face of invasions is greatly increased. The recent introduction to Hawaii of high-density populations of the Puerto Rican coqui tree frog is a special opportunity to study the destabilizing potential of invasions and interactions between invasive species. Actively expanding frog populations are layered onto an older but yet ongoing invasion of a forest type dominated by an Asian tree, albizia. Albizia dominated forest is replacing native Hawaiian ohia tree dominated forest at low elevations. The frogs are small but achieve populations up to 2 frogs per square yard in albizia forest. They represent insertion of a new top predator that may exert control on forest arthropods, like insects, spiders, millipedes, etc., that consume plants (herbivores), prey on each other, and decompose leaf litter (detritivores). We will measure the effects of coqui frogs on albizia-dominated and ohia-dominated forest types by comparing arthropod communities, litter decomposition, and soil nutrients between these two forest types at sites with and without frogs present. We expect to discover the extent to and the means by which the albizia tree invasion and the coqui frog invasion disrupts the food web of the lowland Hawaiian forest. We may also discover aspects of the frog's invasive biology that could prove useful for controlling this recognized pest species in Hawaii including possible regulation of the albizia tree invasion.
