IngentaConnect Population genetic structure of mahogany (Swietenia macrophylla K...

Abstract:

Mahogany (Swietenia macrophylla, Meliaceae) is the most valuable and intensively exploited Neotropical tree. No information is available regarding the genetic structure of mahogany in South America, yet the region harbours most of the unlogged populations of this prized hardwood. Here we report on the genetic diversity within and the differentiation among seven natural populations separated by up to 2100 km along the southern arc of the Brazilian Amazon basin. We analysed the variation at eight microsatellite loci for 194 adult individuals. All loci were highly variable, with the number of alleles per locus ranging from 13 to 27 (mean = 18.4). High levels of genetic diversity were found for all populations at the eight loci (mean H_E = 0.781, range 0.754–0.812). We found moderate but statistically significant genetic differentiation among populations considering both estimators of F_ST and R_ST, thgr

= 0.097 and rho

= 0.147, respectively. Estimates of thgr

and

were significantly greater than zero for all pairwise population comparisons. Pairwise rho

-values were positively and significantly correlated with geographical distance under the isolation-by-distance model. Furthermore, four of the populations exhibited a significant inbreeding coefficient. The finding of local differentiation among Amazonian mahogany populations underscores the need for in situ conservation of multiple populations of S. macrophylla across its distribution in the Brazilian Amazon. In addition, the occurrence of microgeographical genetic differentiation at a local scale indicates the importance of maintaining populations in their diverse habitats, especially in areas with mosaics of topography and soil.

Keywords: Amazon; conservation genetics; genetic structure; mahogany; microsatellites; Swietenia macrophylla; tropical tree

Document Type: Research article

DOI: 10.1046/j.1365-294X.2003.01950.x

Affiliations: 1: Laboratório de Genética e Biologia Reprodutiva de Plantas, Instituto Nacional de Pesquisas da Amazônia, C.P. 478, 69011-970 Manaus-AM, Brazil, 2: Department of Biological Sciences, University of Stirling, Stirling FK9 4LA, UK,

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Population genetic structure of mahogany (Swietenia macrophylla King, Meliaceae) across the Brazilian Amazon, based on variation at microsatellite loci: implications for conservation