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Abstract Detail

Ferns on Oceanic Islands - From Dispersal to Long Lasting Diversity

Janssen, Thomas [1], Rakotondrainibe, F. [2], Bystriakova, Nadia [3], Schneider, Harald [4].

Scaly tree fern radiations in the Madagascan region: neoendemism and recent, coincident diversification bursts.

The Madagascan region, i.e. Madagascar, the Mascarene Islands, the Comoro Islands, and the Seychelles, is renowned for its species richness, distinctiveness of its flora, and high rate of endemism in vascular plants. Development of conservation strategies for the rainforest biome, under strong anthropogenic pressure in the Madagascan region, necessitates an understanding of historical evolutionary dynamics that contributed to shaping its extant diversity. Predominantly African or Asian ancestry and divergence times usually postdating the separation of Madagascar from the Gondwana landmasses have been demonstrated for several Madagascan animal and angiosperm groups. However, studies of rainforest specific lineages such as ferns are scarce and the ecological context of radiation events has often been neglected. As much as 98% of the scaly tree ferns of the Madagascan region are endemic to and an integral and specific component of the local evergreen rainforests Here, we investigate the evolution of these tree ferns, combining results from bioclimatic niche analysis with a dated phylogenetic framework. We show that Madagascar’s extant tree fern diversity springs from three distinct ancestors colonizing the island in the Miocene; that Madagascan tree ferns are most likely of African ancestry with respect to their phylogenetic position and bioclimatic niche preference; and that the three monophyletic and morphologically supported clades diversified in three coincident radiation bursts during the Pliocene, most likely responding to a common climatic trigger. Madagascar then most likely served as a source for the colonization of the surrounding islands, with or without subsequent radiation. The present study adds to evidence that recent punctuated diversification bursts may have played a major role in the evolution of rainforests in the Madagascan region, that these rainforests contain a significant number of young, neoendemic taxa and that they are likely to be an evolutionary source rather than a sink.

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1 - Georg-August-Universität Göttingen, A.-v.-Haller-Institut f. Pflanzenwissenschaften, Abt. Systematische Botanik, Untere Karspüle 2, Göttingen, 37073, Germany
2 - Muséum national d'Histoire naturelle, Dpt. Systématique et Evolution, UMS-CNRS 5202 / USM 602, case postale 39, 57 rue Cuvier, Paris cedex 05, 75231, France
3 - University of Cambridge, Dpt. of Plant Sciences, Plant Ecology, Downing Site, Cambridge, CB2 3EA, UK
4 - Natural History Museum, Cromwell Road, London, SW7 5BD, UK

evolution of biodiversity
Western Indian Ocean
scaly tree ferns
bioclimatic niche analysis
punctuational evolution

Presentation Type: Symposium or Colloquium Presentation
Session: SY11
Location: Lake Michigan/Hilton
Date: Tuesday, July 10th, 2007
Time: 8:45 AM
Number: SY11004
Abstract ID:1169

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