Ant species richness and interactions in canopies of two distinct successional stages in a tropical dry forest.

Abstract

Canopy ecology is a fast-growing field, but still a scientific frontier in many ecological aspects. For instance, the hypothesis that tree traits shape patterns in ant-plant interactions lacks data, notably for tropical canopies in different successional stages. In this study, we investigated canopy traits, such as tree height, the presence of extrafloral nectaries (EFNs), connectivity among tree crowns, and successional stage, structure ant-tree interactions in a tropical dry forest (TDF), examining whether these are the determinant factors for ant species richness. We collected ants on trees in early and late successional stages over 2years, in rainy and dry seasons. In the late successional stage, ant species richness was greater in the taller trees; in the early successional stage, the smallest trees had a greater ant species richness than the taller trees. The EFNs and connectivity among treetops had no effect on ant species richness. We obtained a tree-ant network of the early successional stage, involving 786 interactions among 57 ant species and 75 trees; in the late successional stage, the network had 914 interactions among 60 ant species and 75 trees. There were 27 species of trees in our study, 11 of which (40.7% of all individual trees) had EFNs. The ant-plant interactions were not randomly distributed, suggesting that various biotic factors structured the ant assemblies. This study presents new insights into ant-tree interactions, showing that both tree height and successional stage influence the occurrence of many species of ants in tree canopies of tropical dry forests.