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Spatial Relationships Between Staminate and Pistillate Plants of Dioecious Tropical Forest Trees
K. S. Bawa and P. A. Opler
Vol. 31, No. 1 (Mar., 1977), pp. 64-68
Published by: Society for the Study of Evolution
Stable URL: http://www.jstor.org/stable/2407545
Page Count: 5
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An analysis of the spatial relationships between staminate and pistillate plants of dioecious Guarea luxii, Randia spinosa, Triplaris americana and Zanthoxylum setulosum was made by using Pielou's (1961) nearest-neighbor method. This analysis revealed that staminate and pistillate plants are distributed at random with respect to each other. An examination of the distribution of two sexes along an environmental gradient also revealed no segregation. The results are discussed in relation to a differential niche utilization hypothesis. It is suggested that although there might be selection for exploitation of different habitats by the two sexes, this might be opposed by selection for high pollination levels and increased escape from seed-feeding insects, both of which are probably enhanced by random dispersion of staminate and pistillate plants.The results also suggest that deviations of sex-ratios from one to one, common in tropical forest trees, are not due to greater vegetative multiplication of one sex than the other.
Evolution © 1977 Society for the Study of Evolution