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Effect of habitat fragmentationon the genetic structure of the narrow endemic Brongniartia vazquezii
Jorge González Astorga
Juan Núñez_Farfán
Acceso Abierto
The monoecious, animal-pollinated shrub Brongniartia vazquezii is an endemic and endangered species of the tropical dry forests of Central Mexico. Deforestation of the tropical dry forest has fragmented the habitat and resulted in the isolation of the only four extant populations of B. vazquezii. In this study, we assessed the genetic consequences of habitat fragmentation by comparing the genetic variability (allelic richness and expected mean heterozygosity, He), gene flow and population differentiation in both adult (before fragmentation) and seedling (after fragmentation) populations. Six polymorphic enzymatic loci were used to estimate genetic parameters. F-statistics revealed a deficiency of heterozygous plants in both adults and seedlings in all populations. This probably results from geitonogamous selfing. Genetic diversity was lower in adult than in seedling populations (He = 0.201 and 0.357, respectively). Significant genetic differentiation among populations and of similar magnitude was detected for the adult and seedling populations (Fst = 0.1013 and 0.0705, respectively). Average gene flow between pairs of reproductive populations was high (Nm = 2.23). The genetic structure of adult and seedling populations of B. vazquezii suggests that habitat fragmentation has not reduced, as yet, allelic richness and genetic diversity, nor has it increased genetic differentiation. Furthermore, high levels of gene flow were found, suggesting that habitat fragmentation has broken the former population structure.
Evolutionary Ecology Research
González Astorga J.A., Núñez Farfán J. 2001. Effect of habitat fragmentationon the genetic structure of the narrow endemic Brongniartia vazquezii. Evolutionary Ecology Research. 3: 861-872
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