Cyclones influence native plant diversity on 22 remote high islands of French Polynesia and Pitcairn (eastern Polynesia)

Abstract

I examined the relative influence of eight spatial characteristics on native plant diversity in 22 volcanic high islands of eastern Polynesia. The characteristics used as potential predictors in this study included island area, highest elevation, distance to the nearest continent, distance to the nearest archipelago, distance to the nearest similar island, index of isolation, distance to the largest and highest island of Tahiti, and distance to the “cyclonic alley.” Among characteristics studied, native plant diversity (indigenous and endemic species) was primarily linked with the island area and highest elevation of the islands. Contemporary cyclones were an important predictor of indigenous plant diversity in the remote islands surveyed. In the study area, this result suggests that cyclones, moving from the west Pacific Ocean basin to the eastern Polynesian islands, have provided more indigenous species to the remote high islands located close to the cyclonic alley. Isolation did not appear as a significant predictor of native plant diversity in the high islands surveyed, possibly due to a stepping-stone-island effect and the proximity of the cyclonic alley. These findings suggest that isolation could be tempered by a cyclonic-transport-flow effect in the study area, thus reducing the effective distance of the remote islands from the mainland source pool for seed dispersal.

Keywords:

• abiotic factors
• cyclone alley
• eastern Polynesia
• island biogeography
• native plant diversity

Acknowledgments

I am grateful to the “Ministère de l’Ecologie” (Paris, France) for their financial support for the mission in French Polynesia. I want to thank my colleagues Christophe Corona and Johannes Steiger (CNRS, UMR 6042, GEOLAB, France) for providing useful comments on an early version of this paper and revising the English.