Sexual systems of Tropical Dry Forest trees in restored habitats

Abstract

Background: Obligate outcrossing species (such as dioecious species) are more vulnerable to habitat fragmentation than self-compatible hermaphrodite trees.
 Questions: What is the effect of restoration intervention in the populations of dioecious, monoecious, and hermaphrodite tree species in permanent agricultural landscapes?
 Study site and dates: 8-year-old restoration settings in the seasonally dry tropical forest in Sierra de Huautla Biosphere Reserve, Morelos, Mexico.
 Methods: We measure richness and density of dioecious, monoecious, and hermaphrodite tree species with Diameter at Breast Height ≥ 2.5 cm in perturbed, 8-year-old restoration settings (plantings and natural succession) and conserved habitats.
 Results: Overall habitats, 2,042 trees from 46 species in 18 families were identified; the highest percentage of species and trees were hermaphrodites (63 % of species and 78 % of trees), the lowest percentage of species were monoecious (9 %) and the lowest percentage of trees (10 %) were dioecious. In the plantings were registered the largest number of species (37 species) and in the conserved habitat the largest number of trees (852 trees). Density and richness of dioecious, monoecious, and hermaphrodite species did not differ by habitat, contrary to our predictions. For dioecious trees, the restored and conserved habitats showed similar composition heterogeneity. Composition of hermaphrodites in agricultural landscapes differed the most with the conserved habitat.
 Conclusions: Dioecious and monoecious species are favored in agricultural landscapes due to their use value. Selection of species for restoration plantings should consider sexual systems of trees to recover not only forest structure but also ecosystem function.