Habitat differences in seed-dispersing vertebrates indicate dispersal limitation in tropical bracken-dominated deforested areas

Abstract

Shifting agriculture and anthropogenic fires are among the main causes of deforestation in the tropics. After fire and land abandonment, vast deforested areas are commonly dominated by the bracken fern Pteridium for long periods. Although forest regeneration in bracken-dominated areas is mainly hindered by dispersal limitation, little is known about the role of seed-disperser communities in slow forest succession. Our objective was to unravel the differences in the properties of the seed-disperser communities between forests and bracken-dominated areas to assess their role in dispersal limitation to foster ecological restoration. We compared species richness, diversity, abundance, and composition of seed-dispersing birds, bats, and medium and large terrestrial mammals between both habitats in a montane forest of Bolivia. The species richness and diversity were similar for bats and higher for birds in bracken-dominated areas than in the forest, but species composition was different between both habitats and groups. Although species composition was similar between both habitats for terrestrial mammals, the abundance was higher in the forest than in bracken-dominated areas. Differences in species composition of seed-dispersing birds and bats could be one of the main causes of dispersal limitation in forest regeneration in tropical bracken-dominated areas. The few shared species between both habitats could explain the low seed rain of animal-dispersed forest tree species in bracken-dominated areas and the consequent hindered forest regeneration. Future studies relevant to natural forest regeneration should focus on analyzing the effects of animal-attractants such as perches, artificial bat-roosts, and seedling transplants on disperser communities, seed dispersal effectiveness, and forest regeneration.