Report for the 2002 Pacific Biological Survey, Bishop Museum Austral Islands, French Polynesia Expedition to Raivavae and Rapa Iti

The Pacific Biological Survey (PBS) of the Bishop Museum conducted biological surveys on the Austral Islands of Raivavae and Rapa as part of an "Inventaire et Valorisation de la Biodiversite" or inventory and evaluation of biodiversity, a research program conducted in French Polynesia with the assistance and support of the Delegation a la Recherche (Ministere de la Culture, de l'Enseignement Superieur et de la Recherche, Gouvernement de la Polynesie francaise). The objectives of the PBS Bishop Museum surveys in the Austral Islands were: 1) to assess the native aquatic insect fauna and describe the overall biodiversity of this fauna, 2) assess the biodiversity and status of Heteroptera and other important insects in native forest areas, 3) to assess the impacts or lack of impacts of introduced aquatic species on native stream biota, 4) to qualitatively assess the impacts of introduced species, feral ungulates, urbanization, on native insects, and 5) to provide museum specimens and an information baseline for future researchers.Significant findings of these surveys include a pristine native freshwater fauna lacking introductions of nonindigenous fish, amphibians, or aquatic reptiles on both Rapa and Raivavae Islands. Extensive research in Hawaii has shown the devastating impacts of alien fish species on the native stream fauna, and every effort should be made to avoid introductions of any non-native aquatic species to Rapa and Raivavae. Numerous undescribed aquatic insect species were found in Rapa and Raivavae, including new species andrange extensions of Heteroptera (true bugs), Diptera (aquatic flies), and Odonata (dragonflies and damselflies). A rich terrestrial native insect fauna with numerous undescribed species of Coleoptera (beetles), Diptera (flies), Heteroptera (true bugs), and Homoptera (planthoppers) and was also found on Rapa and Raivavae, although stands of native forest habitat for these insects were found to be severely reduced on both islands. The native species found on both islands are important on a worldwide basis, and preservation of this biodiversity is critical in preserving the rich Polynesian culture found on these islands. It is also necessary to preserve biodiversity to allow a greater understanding of the natural biological processes of dispersal and colonization of the fauna to these remote and isolated island areas. Native forests on Raivavae and Rapa were found to be critical for the survival of both the terrestrial and aquatic fauna of the Austral Islands. A good example of this interrelationship between forests and aquatic habitats is found with the damselflies on both Rapa and Raivavae that are aquatic during their immature phase, but as adults require forested areas to forage for food. The endemic native damselfly on Rapa was only found in forested areas, and never observed during sampling along many kilometers of deforestedstream habitat. Native vegetation was also critical for the newly found species of Raivavae damselfly, with this species also having similar forest requirements. Most of the native terrestrial insect biodiversity remaining on the island of Rapa is found in a narrow zone of native forest between 450-650 m at the summit of Mt. Perau. The collection of many undescribed species from Mt. Perau illustrates the point that despite two monographic works on the Lepidoptera and Miocalles weevils from Rapa, much remains to be studied on the insect fauna from this most intact native forest found on Rapa. To preserve a rich native biodiversity and Polynesian cultural heritage, it is imperative to protect the limited remaining native forests on Raivavae and Rapa. Working with the inhabitants of each island, forest reserve areas should be set up to protect the most important and biologically diverse areas. The areas that should receive the highest priority for protection would be the Mt. Perau area on Rapa, and the Mt. Hiro summit region and associated gulches on Raivavae.