Invasive Frogs’ Influence on Lowland Forest Arthropod Communities and Ecological Processes in Hawaii

We conducted an enclosure experiment at two low­land sites on the eastern side of the Island of Hawaii for 6 months (September 2004 to February 2005) to determine the effect of Eleutherodactylus coqui on 1) three invertebrate communi­ties (aerial, herbivorous, and leaf litter), 2) nutrient cycling rates and leaf litter decomposition rates, and 3) native and non-native plant growth rates. E. coqui was found to reduce all invertebrate communities at one study site, while the other site did not have any difference with treatment. At both sites, herbivory rates were lower in the presence of E. coqui than in their absence. At both sites, E. coqui was associated with increased NH4+ in leaf washes, increased K, Mg, N, and P concentrations in the leaf litter, and increased decomposition of leaf litter. P. cattleianum had more new leaves in presence of the E. coqui than in the absence of E. coqui across sites. Non-native plants had higher survivorship than native plants. In summary, invertebrate community responses to E. coqui differed by site but ecological processes responded similarly across sites. Path analyses suggest that the E. coqui increases leaf litter decomposition and non-native plant growth rates by making nutrients more available to microbes and plants. These findings are of concern in Hawaii, where E. coqui can potentially affect the 44 endangered invertebrates and potentially increase non-native plant growth