RESUMO
BACKGROUND AND AIMS: Genetic structure and variability were examined in the only three extant populations of the narrow-endemic tree Antirhea aromatica (Rubiaceae, Guettardeae), an endangered species of the tropical forest of eastern Mexico. Patterns of genetic diversity within and among populations for adult plants and seedlings were obtained. METHODS: Allozyme electrophoresis of 15 loci was conducted and the data analysed with statistical approximation for obtaining genetic diversity, structure and gene flow. KEY RESULTS: The mean expected heterozygosity (He) in the adult and seedling populations was 0.18 +/- 0.08 and 0.20 +/- 0.09, respectively. The genetic variation explained by differences among populations was 51 and 35 %, for adult and seedling populations, respectively. On average, gene flow between paired adult populations was low (Nm = 0.26 +/- 0.09), compared with other trees from the tropical forest. CONCLUSIONS: The results indicated that the populations evaluated have high genetic variability, compared with other endemic and geographically narrowly distributed plant species, in areas with high levels of environmental heterogeneity (e.g. tropical forests). The conservation implications of the results are discussed, and in this regard it is proposed that A. aromatica should be considered as an indicator species with economic potential. It is suggested that sustainable management practices should be implemented and that the areas where the species is distributed should be declared a natural reserve to ensure the species conservation.