Muthu Rajkumar, Richard Randrianaivo, Runguo Zang, Fidy Ratovoson, Chris Birkinshaw, Timothy J. S. Whitfeld, Rebecca Ostertag, Miramasoandro Randrianjanahary, Ludovic Reza, Janet Franklin, Shin-ichiro Aiba, Christian P. Giardina, Creighton M. Litton, Melinda Laidlaw, Narayanaswamy Parthasarathy, Heike Culmsee, Susan Cordell, Philippe Birnbaum, Lawren Sack, Thomas Ibanez, Gunnar Keppel, Edward L. Webb, Cláudia Baider, Ladan Rasingam, Thomas W. Gillespie, F. B. Vincent Florens, Tara G. Martin, Institut Agronomique Néo-Calédonien (IAC), Curtin Biodiversity and Climate Institut, Missouri Botanical Garden, Department of Geography, Escuela Militar de Ingeniería (EMI), Ecosystem Sciences, CSIRO Ecosystem Sciences, CSIRO Ecosystem Sciences-CSIRO Ecosystem Sciences, Parc Botanique et Zoologique de Tsimbazaza, BP 4096, Antananarivo, Madagascar, Parc Botanique et Zoologique de Tsimbazaza, University of California [Los Angeles] (UCLA), University of California, Grad Sch Sci & Engn, Kagoshima University, Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), Département Systèmes Biologiques (Cirad-BIOS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Ibanez, Thomas, Keppel, Gunnar, Baider, Cláudia, Birkinshaw, Chris, Birnbaum, Philippe, Missouri Botanical Garden (USA), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), and University of California (UC)
Aim: To determine the role of regional forcing on plot-level species diversity and composition, and to quantify the relative importance of biogeographical and climatic factors in explaining woody plant diversity and composition at the local-, island- and archipelago-scale. Location: Forty-one tropical islands of the Indo-Pacific region from Madagascar to Hawai‘i Island. Methods: We analysed the diversity and composition of tropical woody plant communities located across 113 plots, 41 islands and 19 archipelagos. We used generalized linear mixed-effects models and generalized dissimilarity models to determine the role of regional forcing at the island and archipelago scale and to assess the relative importance of biogeographical (area and isolation of islands or archipelagos, geographical distance between plots) and climatic factors in explaining differences in local diversity and composition (species turnover). Analyses were conducted at different geographical scales (local, island and archipelago) and taxonomic levels (species, genus and family). Results: Variation in local (plot-level) diversity (as species density, the number of species per 100 woody plants) was primarily explained by island and archipelago identity. Maximum species density was positively correlated with the area of an island (or archipelago) and negatively correlated with the isolation of an archipelago. Local climatic variability was also a significant predictor of species density, but less important than regional forcing. Climate variables explained < 20% of the variation in species turnover across all plots. The importance of geographical distance between plots relative to climate in driving species turnover decreased from the species to family level, and from the regional to island level. Main conclusions: Regional forcing was the key driver of local diversity and composition on islands. Island area and archipelago isolation are likely driving local diversity through their effects on the pool of island species. Geographical distance between plots is the main factor explaining species turnover, while at higher taxonomic levels, climatic factors and niche conservatism are the main drivers. Refereed/Peer-reviewed