Spatial genetic structure within size classes of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae)
Fuchs Castillo, Eric J.
Hamrick, James L.
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Premise of the study: Patterns of spatial genetic structure (SGS) were analyzed within a population of the endangered tropical tree Guaiacum sanctum located in northwestern Costa Rica. Documentation of these patterns provides insights into the gene dispersal mechanisms that play a central role in the maintenance and structure of genetic diversity within plant populations. • Methods: Allozyme analyses were used to examine SGS in Palo Verde National Park, Costa Rica. The SGS was compared among three plots and different age classes. • Key results: High levels of genetic diversity were found overall with a pooled genetic diversity of He = 0.302 ( ± 0.02). Selfi ng was proposed as the proximate cause for signifi cant levels of heterozygote defi ciency observed across size classes and plots. An unexpected lack of SGS ( rj < 0.02) was observed for all size classes, suggesting the mixing of seeds from several adults. A parent-pair parentage analysis indicated that at least 48% of the smaller individuals within a plot were produced by parents located at distances of at least 150 m. • Conclusions: Populations of G. sanctum are established and maintained by bird-mediated, moderate- to long-distance seed dispersal, which results in a mixture of seeds from unrelated maternal individuals, effectively eliminating SGS. Proximity between individuals is, therefore, a poor predictor of family structure in this species. Long-distance seed dispersal, coupled with estimates of high genetic diversity, suggests that this endangered species has the potential for natural regeneration and restoration given the availability of suitable habitats.
External link to the item10.3732/ajb.0900377
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