Biodiversity and biogeography of Henderson Island's insects

Abstract

Henderson Island is an example of a raised coral atoll, and as such supports a much more diverse biota than geographically similar low atolls. It is also, due to its remote location, largely undisturbed by the activities of humans. It is therefore unique in the Pacific Ocean, and comparable to Aldabra in the Indian Ocean. Biogeographically it is also interesting as it is amongst the most easterly islands of the Indo-West Pacific region, and has been largely colonized by species dispersing from island to island across the ocean from the west. New and extensive collections of insects were made in 1991. Although not fully identified yet, it is clear that the fauna is depauperate, with only about 180 species known to date. Despite its easterly location almost all species are derived from the west, and much of the fauna is likely to be indigenous. The most diverse orders are the Lepidoptera (c. 53 spp.), Coleoptera (c. 38 spp.), Diptera (c. 37 spp.), Hymenoptera (c. 21 spp.), Homoptera (c. 14 spp.) and Heteroptera (4 spp.). Of particular interest are the weevils, Heteroptera and Homoptera which exhibit considerable endemism with perhaps some examples of intra-island radiation. Although depauperate, Henderson supports a much larger insect fauna than that of nearby Ducie Atoll (total known insect fauna = 15 spp).