Ferns on Oceanic Islands - From Dispersal to Long Lasting Diversity
Bystriakova, Nadia , Kunstler, Georges .
Comparing tree fern diversity on tropical and non-tropical oceanic islands using climatic niche modelling approach.
Despite the apparent differences in the land area, climate and biogeographic history, both Madagascar and New Zealand harbour a variety of tree ferns of the family Cyatheaceae, which make major contribution to the biodiversity of forest ecosystems of these islands. However species diversity of Cyatheaceae in Madagascar is much higher than that in New Zealand. While nearly 50 species and subspecies of scaly tree ferns have been described in Madagascar, there are only 7 species of Cyatheaceae in New Zealand, two of them endemic to Kermadec Island. To explain the disparities in species numbers, we analysed the relationship between island area, habitat diversity and species richness. We hypothesise that the differences in species diversity in Madagascar and New Zealand might also arise from the climatic history of these islands. We compiled available data on the tree fern diversity on several oceanic islands. Multiple regression analyses were used to investigate the relationship between species richness and the pair of independent variables, area and habitat diversity, defined for the purposes of the present study as maximum elevation. Tree fern distribution data were obtained from several electronic databases and digitised herbarium collections. For each location point, corresponding values of selected environmental variables were obtained using GIS. To model and separate climatic niches of individual species and clades in the environmental space, a multivariate ordination technique, Outlying Mean Index analysis, was used. To investigate the role of Pleistocene climates in creating opportunities for speciation of Cyatheaceae in Madagascar and New Zealand, we modelled changes in the extent of the climatic niches under different climatic regimes. Our results suggest that during the glacial-interglacial cycles in NZ tree fern distributions mostly experienced latitudinal contractions and expansions, whereas in Madagascar the altitudinal movement was more pronounced.
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1 - University of Cambridge, Dpt. of Plant Sciences, Plant Ecology, Downing Site, Cambridge, CB2 3EA, UK
2 - Cemagref Grenoble, Unit Mountain Ecosystems, 2 rue de la Papeterie, St-Martin-D'Heres cedex, BP 76 38402, France
Presentation Type: Symposium or Colloquium Presentation
Location: Lake Michigan/Hilton
Date: Tuesday, July 10th, 2007
Time: 9:30 AM