Diversity patterns along ecological succession in tropical dry forests: A multi-taxonomic approach

Evaluating the diversity of multiple taxa is fundamental to understand
community assembly and to assess the integrity and functionality of
tropical secondary forests. In this study, we analyzed the natural
regeneration of tropical dry forests (TDFs) in three regions of Brazil
using Hill-Simpson diversity, abundance and β-diversity of trees and five
groups of insects (herbivores, fruit-feeding butterflies, ants, culicid
mosquitoes and dung beetles). Sampling was conducted in 39 0.1 ha plots
using a chronosequence approach (13 plots in early, intermediate and
old-growth forests). We evaluated the contribution of three different
levels to γ-diversity: α (within plots), β¹ (among plots) and β² (among
successional stages), and further determined the relative importance of
turnover (species replacement) and nestedness (differences in species
number among sites) to β². Our results showed that, unexpectedly, the
Hill-Simpson diversity was consistently higher in early than old-growth
stages for all regions, but varied more widely in the intermediate stages.
For each group separately, the same trend was observed for butterflies,
ants, dung beetles and herbivores and did not differ among stages for
mosquitoes. Successional differences in abundance were only detected for
trees (increasing along the gradient) and for mosquitoes (decreasing).
According to our expectations, the additive partitioning analysis showed
that β2-diversity contributed more to γ-diversity than β1-diversity, when
all taxa were considered together and for most of them separately (except
for butterflies and dung beetles). Most of the β²-diversity was due to
species turnover, but this contribution varied among groups and regions,
with the highest turnover for herbivores and the lowest for dung beetles.
Our results suggest that the Hill-Simpson diversity and changes in species
composition (as given by β²-diversity) are better indicators of forest
natural regeneration than raw species richness, corroborating previous
studies with plants and animals.