Evol Ecol Res 3: 861-872 (2001) Full PDF if your library subscribes.
Effect of habitat fragmentation on the genetic structure of the narrow endemic Brongniar tia vazquezii
and Juan Núñez-Farfán2
1Jardín Botánico Clavijero, Instituto de Ecología, A.C., km 2.5 An tigua Carretera a Coatepec, Xalapa 91000, Veracruz and 2Departamento de Ecología E volutiva, Instituto de Ecología, UNAM, Apartado Postal 70275, C.P. 04510 D.F., México
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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. va zquezii. In this study, we assessed the genetic consequences of habitat fragmentation by comparin g the genetic variability (allelic richness and expected mean heterozygosity, He), gene flow and population differentiation in both adult (before fragmentation) and seedling (after fr agmentation) 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 al l populations. This probably results from geitonogamous selfing. Genetic diversity was lower in adul t than in seedling populations (He = 0.201 and 0.357, respectiv ely). Significant genetic differentiation among populations and of similar magnitude was detected fo r 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, su ggesting that habitat fragmentation has broken the former population structure.
Keywords: Brongniartia vazquezii, conservation genetics, endemic and narrow species, gene flow, genetic structure, habitat fragmentation, Mexico.
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