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Abstract Detail


Ecological Section

Hong-Wa, Cynthia [1], Distler, Trisha [2], Schatz, George E. [3], Lowry, Porter P. II [4], Jimenez, Ivan [5].

Determinants of broad-scale plant species richness across Madagascar.

Understanding broad-scale patterns of species richness is a central issue in ecology and biogeography. Four prominent hypotheses suggest that these patterns are determined by gradients of energy and water availability (the species-energy hypothesis), variation in topography and habitat (the spatial heterogeneity hypothesis), geometric constraints imposed by landmasses on the location of species geographic ranges (the geometric constraints hypothesis), and human activities that decrease species richness through the contraction of species geographic ranges (the anthropogenic extinction hypothesis). Using spatial regression models we examined the relative merit of these hypotheses by simultaneously confronting their predictions against an estimate of the broad-scale spatial pattern of vascular plant richness across Madagascar. We estimated plant richness at a 100 × 100 km resolution using 54,512 geo-referenced herbarium specimen records (representing 7,319 plant species), correcting for sampling effort through rarefaction. These data lent more support to the spatial heterogeneity and the anthropogenic extinction hypotheses than to the species-energy and the geometric constraints hypotheses, suggesting a dominant role of spatial heterogeneity (in elevation and climate) and anthropogenic impacts (on primary vegetation) in shaping the contemporary broad-scale pattern of plant species richness across Madagascar. The spatial regression models best supported by the data predicted that the highest plant species richness is largely restricted to topographically complex areas of the island, including the Tsaratanana region, the region between Masoala and Toamasina, and the Mandrare region.


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1 - University of Missouri-St. Louis, Department of Biology, One University Blvd., St. Louis, MO, 63121-4499, USA
2 - Missouri Botanical Garden, Center for Conservation and Sustainable Development, P.O. Box 299, St. Louis, Missouri, 63166-0299, USA
3 - Missouri Botanical Garden, Po Box 299, St Louis, Missouri, 63166-0299, USA
4 - Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri, 63166
5 - Missouri Botanical Gardens, Center for Conservation and Sustainable Development, 4344 Shaw Boulevard, Saint Louis, MO, 63110, United States

Keywords:
Madagascar
Plant species richness
Spatial heterogeneity
Anthropogenic extinction
Geometric constraints
Species-energy.

Presentation Type: Oral Paper:Papers for Sections
Session: 30
Location: 212/SUB
Date: Tuesday, July 29th, 2008
Time: 9:30 AM
Number: 30005
Abstract ID:843


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