Does the invasive tree, Falcataria moluccana facilitate high population density of the invasive Puerto Rican frog, Eleutherodactylus coqui

The Puerto Rican treefrog, Eleutherodactylus coqui , is a new invasive species in Hawai‘i, and its large expanding populations represent an important new predator influence on Hawaiian forest invertebrates. I studied whether a nitrogen fixing tree, Falcataria moluccana (albizia) facilitates the population density of the E. coqui. It was hypothesized that albizia-dominated forest increased the population density of prey items for E. coqui, thereby allowing the population density of frogs to increase. I conducted a mark and recapture study during the dry season (kau wela) in 2006 and wet season (ho‘oilo) in 2007 to measure frog population characteristics in invasive albizia-dominated forest and native Metrosideros polymorpha (‘ōhi‘a)-dominated forest. Frog population densities were variable within, but overall similar between, both forest types, refuting the initial hypothesis. However, either of these forest types can support coqui populations that are denser than those found in their native Puerto Rico habitat. Such high densities of coqui frogs in native dominated Hawaiian forests are a strong potential threat to native forest invertebrates and possibly to their native predators. In addition, dense populations of E. coqui could facilitate the colonization of new alien species into native forest ecosystems.