Influence of the leaf-cutting ant Atta sexdens Linnaeus (1758) on the taxonomic and functional diversity of woody plants in Atlantic Forest fragments

Abstract

Abstract Leaf-cutting ants can act as a biotic filter, selecting plant traits according to foraging preferences, affecting plant community species composition. We evaluated the relationship between the floristic and functional diversity of woody plants in fragments of Semideciduous Seasonal Atlantic Forest (SAF) with the presence or absence of Atta sexdens (Linnaeus, 1758) nests. We expected that, in places where A. sexdens nests are present, floristic diversity is lower and the plant community is dominated by species characterized by more anti-herbivore defenses and lower nutritional content. We sampled nine SAF fragments in the northern Paraná state, Brazil. The diversity of woody regenerants (> 1m in height, <2cm diameter) was estimated and ten functional traits were evaluated: gap dependence, deciduousness, leaf nitrogen and carbon content, leaf C/N ratio, leaf trichomes, leaf thickness, specific leaf area, presence of latex and condensed tannins. Contrary to expectations, there were no differences in floristic diversity between sites with or without A. sexdens, and functional diversity was also similar, reflecting the floristic similarity. We suggest that the herbivory pressure by A. sexdens on the woody regenerants of SAF fragments is not strong enough to cause significant mortality in individual species and, consequently, affect plant diversity and composition. This may in part be related to the fact that most A. sexdens nests are established in the edges of the fragments and that ants from these nests also forage in the agricultural matrix. Longer-term studies are still needed to fully elucidate the effects of A. sexdens on Atlantic Forest fragments.