Impoverished Freshwater Fauna of Easter Island

The fauna and flora of Easter Island is not only impoverished; the share of invasive species is impressive (Campos and Pena 1973; Desender and Baert 1996). The freshwater microfauna of the island had been neglected until recently. The presence of mosquitoes was, of course, known, and had given rise to the introduction of an insectivorous fish that may have had effects on other faunal elements as well. Yet, among insects, it is reasonably certain that only a single dragonfly species (Pantala flavescens) ever existed on the island. The fact that, at times, it shows an atypical behavior here (Dumont and Verschuren 1991) does not exclude the possibility that this long-ranging migrant, which may move with ocean-going ships, was a recent arrival on the island. The single aquatic beetle species known from Easter Island, Bidessus skottsbergi was decribed from Rano Kao in 1924 (Zimmerman 1924) prior to the introduction of the fish. It has not been collected since. Its status a an endemic is under question: Desender and Baert (1997) argue that Kuschel (1963) was probably right in considering it synonymous to an Australian species.