Micronesica 41(1): 131–164, 2009 Plant Endemism, Rarity, and Threat in Palau, Micronesia: A Geographical Checklist and Preliminary Red List Assessment 1 CRAIG M. COSTION Department of Ecology and Evolutionary Biology, School of Earth and Environmental Sciences, University of Adelaide, Adelaide SA 5001
[email protected] ANN HILLMANN KITALONG The Environment, Inc., P.O. Box 1696, Koror, Palau 96940 TARITA HOLM Palau Conservation Society/PALARIS, P.O. Box 1811, Koror, Palau, 96940 Abstract—An official checklist of the endemic plant species of Palau has been long awaited, and is presented here for the first time. For each species a substrate limitation, growth form, and relative abundance is listed. In addition an IUCN red list assessment was conducted using all available data. For over half of the endemic species there is insufficient data to provide a red listing status however an expected minimum number of threatened plants out of the total is inferred. Approximately 15% of Palau’s endemic plants are believed to be only known from the type collection and many more only known from a few collections. These taxa however may now be prioritized and targeted for future inventory and research. The taxonomic robustness of several of these taxa is questionable and it is expected that more endemic species will be lost to synonymy in the future. Previous estimations have significantly over-estimated the rate of plant endemism in Palau (e.g., 194). Here, 130 plants are recognized for Palau, making its level of plant endem- ism comparable to some of its neighboring Micronesian islands to the east, notably Guam and Pohnpei.