1. ¹Pós-Graduação em Biotecnologia, Universidade Católica de Brasília, SGAN 916, Mod. B, Brasília D.F., Brasil 70-970-160
2. ²Departamento de Ecologia, Universidade de Brasília, Brasília, D.F., Brasil 70910-900
3. ³Laboratório de Genética de Plantas, Recursos Genéticos e Biotecnologia – EMBRAPA, C.P. 02372, Brasília, D.F., Brasil 70770-900

Correspondence: Rosane Garcia Collevatti, E-mail: rosanegc@pos.ucb.br

Received 12 November 1999; Accepted 3 October 2000.

Abstract

In this work we investigate the mating system of four populations of the endangered tropical tree species Caryocar brasiliense, using genetic data from 10 microsatellite loci. Eight to 10 open-pollinated progeny arrays of 16 individuals, together with their mother tree, were sampled per population. Mating system parameters were estimated under the mixed mating model, implemented by the software MLTR. The single-locus outcrossing rate (t_s) varied among loci and populations, but multilocus outcrossing rates (t_m) were equal to one for all four populations. Nevertheless, biparental inbreeding (t_m - t_s) was different from zero for all populations, indicating that outcrossing events may occur between relatives. Our results also indicate that the high polymorphism of microsatellite markers provide an extraordinary resolution to discriminate precisely selfing events from outcrossing events between close relatives. Our results indicate that, although highly outcrossed, C. brasiliense shows high levels of biparental inbreeding, most likely due to the limited flight range of pollinators and restriction in seed dispersal. Furthermore, these results suggest that Cerrado fragmentation could limit gene flow by isolating seed dispersers and territorial small sized bat pollinators inside fragments, increasing the rate of mating between close relatives. The conservation of nonisolated populations in large preserved areas may be necessary to foster outcrossing events between unrelated individuals and thus maintain species viability.