Background and Aims:

Genetic variation of tree species is poorly understood for tropical forests of Mexico. The objective was to analyze the genetic diversity of Brosimum alicastrum (Moraceae) and Sapium macrocarpum (Euphorbiaceae), successionally intermediate species and dispersed by animal (zoochory), and Cecropia peltata (Cecropiaceae) and Heliocarpus appendiculatus (Malvaceae), early successional or pioneer, zoochory and anemochory dispersal syndrome, respectively, of the semi-evergreen forest of the Selva El Ocote Biosphere Reserve (REBISO), Chiapas, Mexico.

Methods:

Two DNA regions of the ribosomal nuclear gene, ITS 1-2 and ITS 3-4, were amplified as genetic markers. DNA was extracted from leaves or cambium of trees of the chosen species from three locations (or subpopulations) in the REBISO. From concatenated sequences (578 bp), the estimators of genetic diversity were obtained.

Key results:

Eight haplotypes were recorded in B. alicastrum, 12 in S. macrocarpum, five in H. appendiculatus and six in C. peltata. The highest values for most of the diversity estimators were observed in S. macrocarpum (π = 0.047, Hd = 0.79, s = 10), and the lowest differentiation between subpopulations was also recorded in this species (Φst = 0.22). In contrast, H. appendiculatus and C. peltata presented lower values but greater differentiation between the subpopulations (Φst ~ 0.80).

Conclusions:

Overall, the highest level of genetic diversity was recorded for S. macrocarpum, a successionally intermediate species and with zoochorous dispersal syndrome. Less variation was observed within species and greater differentiation in successionally pioneer species, H. appendiculatus and C. peltata. The genetic variation observed fits well a neutral evolutionary model; therefore, the pattern of genetic variation probably was driven by random evolutionary processes. However, the dispersal syndrome and successional affinity influence spatial distribution of genetic diversity.

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