Rapa Iti is a small (38 km2), volcanic, oceanic island. It is located at 27° 36´ south latitude and 144° 17´ west longitude and is 650 km south southeast of Tahiti and 200 km southeast of Raivavae, the nearest island in the Austral archipelago. The island is the remains of a volcanic cone which collapsed on one side making the aerial view of the island resemble the letter “C” surrounding a large lagoon. The view from the lagoon reveals an amphitheater of towering peaks connected by razor-shape ridges. The highest peak on the island reaches 650 m in elevation and several others are well over 400 m in height. The geographic location 400 km south of the Tropic of Capricorn and resulting temperate climate make Rapa Iti the most botanically unique and a plant diversity hotspot for French Polynesia. Scientists have found the vegetation of Rapa Iti to be one of the most difficult to classify. It contains two endemic, monospecific genera (Apostates, Asteraceae and Metatrophis, Urticaceae), four species in genera endemic to French Polynesia (Oparanthus, Apetahia, Haroldiella), and Eastern Polynesia (Fitchia), and genera found elsewhere only in New Zealand, Australia, and or Hawai`i. This makes the island a keystone to understanding the biogeography, phylogeny, and origin of many Pacific plant lineages (Geniostoma, Hebe, Corokia, and Nesoluma). Unfortunately, the forests of Rapa are theatened by deforestation, fire, goats, and cattle. This paper presents results of data collected during a recent botanical expedition to Rapa and an overview of the flora of the island, it’s relationships to other Pacific island floras, and conservation issues and concerns.

Key words: Biogeography, Floristics, Geniostoma, Hebe, Pacific, Rapa Iti