Abstract

TRUJILLO-SIERRA, José Enrique et al. Genetic variation in Mexican populations of Swietenia macrophylla King, a tropical species in recent geographic expansion. Bot. sci [online]. 2013, vol.91, n.3, pp.307-317. ISSN 2007-4476.

Swietenia macrophylla King is a tropical species that historically had been exploited as a timber resource of high quality and currently listed as threatened of extinction. The present study evaluated genetic variation and structure of six fragmented populations of S. macrophylla from the Yucatan Peninsula and southern Veracruz, Mexico, using four reproducible and polymorphic nuclear microsatellites. A moderate value of genetic variation was found (H_E = 0.600), and a high and significant coefficient of inbreeding (F_IS = 0.309; P = 0.0001). The effective population size (N_E) was heterogeneous among populations with an average of 19.4. The genetic structure was moderate but significant (F_ST = 0.095) and the migration rate high (M > 3.83). Two and three highly differentiated groups were defined with the dendrogram and the Bayesian inference analyzes of spatial and genetic structure; however, the isolation by distance analysis between pairs of populations was not significant (P = 0.486). The results provide us evidences of S. macrophylla is susceptible to lost genetic variation to habitat fragmented, and support a recent expansion hypothesis based on the founder effect of some genotypes. Finally two probable dispersal routes are suggested; the first through the Caribbean zone and the second in the Gulf of Mexico coastal.

Keywords : expansion; genetic variation; habitat fragmentations; mahogany; Mexico.

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