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Plant Reproductive Ecology of a Secondary Deciduous Tropical Forest in Venezuela

Thirza Ruiz Zapata and Mary T. Kalin Arroyo
Biotropica
Vol. 10, No. 3 (Sep., 1978), pp. 221-230
DOI: 10.2307/2387907
Stable URL: http://www.jstor.org/stable/2387907
Page Count: 10
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Plant Reproductive Ecology of a Secondary Deciduous Tropical Forest in Venezuela
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Abstract

The breeding systems, reproductive efficacies, and densities of selected trees, shrubs, vines, and hemiparasites of a secondary deciduous mid-elevation tropical forest in Venezuela are investigated. A total of 77.17 percent of the species studied are adapted for obligate outbreeding, 54.45 percent through the possession of genetic self-incompatibility, and 22.72 percent by way of dioecy or functional dioecy. Reproductive densities (density of flowering individuals) vary from 2.0 to 165.9 individuals per species per hectare with a mean of 10.7 and median of 5.0. Hemiparasites and vines form denser populations than do trees and shrubs. The densities of tree and shrub species are similar. All species, whether obligately outbred or genetically self-compatible, set abundant seed under the ecological conditions of the community. Distance between the individuals of a population does not limit seed set under obligate outbreeding. The reproductive efficacies of dioecious species are higher than those of genetically incompatible hermaphrodites. Non-autogamous compatible hermaphrodites set a lower percentage of seed than do autogamous hermaphrodites. The proportion of outbreeding species in the secondary tropical forest is similar to that reported for a speciose tropical deciduous forest in Costa Rica; however, the species of the secondary forest exhibit higher reproductive efficacies. Factors favoring the maintenance of high proportions of obligately outbred species in species-rich tropical ecosystems are discussed.

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