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Endemic Areas and Geographic Speciation in Tropical American Ferns

Rolla Tryon
Biotropica
Vol. 4, No. 3 (Dec., 1972), pp. 121-131
DOI: 10.2307/2989774
Stable URL: http://www.jstor.org/stable/2989774
Page Count: 11
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Endemic Areas and Geographic Speciation in Tropical American Ferns
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Abstract

The species of continental tropical American ferns are concentrated in three primary geographic areas, the Mexican, the Andean and the Brazilian, and two secondary areas, the Central American and Guayanan. These regional centers contain about 90 percent of the continental fern flora, and about 60 percent of these species are endemics. The intervening areas between the centers are relatively poor in species and especially in endemics. The regional centers are distinctive floristic-geographic regions. Their location and environmental history have had a major role in the development of the tropical American fern flora by the processes of geographic speciation: regional isolation, long-distance migration, and peripheral divergence. The spores of ferns have a high dispersal capacity, but geographic isolation may be effective at distances within the dispersal range especially if enforced by ecological isolation. Speciation by peripheral divergence has been especially important in the development of the high numbers of species and endemics that characterize the primary regional centers.

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