Leaf-cutting ants alter seedling assemblages across second-growth stands of Brazilian Atlantic forest

• Published in: Journal of tropical ecology 2012-07, Vol.28 (4), p.361-368
• Main Authors: Silva, Paulo S. D., Leal, Inara R., Wirth, Rainer, Melo, Felipe P. L., Tabarelli, Marcelo
• Format: Article
• Language: English
• Subjects: Abundance; Animal and plant ecology; Animal populations; Animal, plant and microbial ecology; Ants; Atta cephalotes; Biological and medical sciences; Defoliation; Foraging; Foraging behavior; Forest ecology; Forest ecosystems; Forest regeneration; Fundamental and applied biological sciences. Psychology; Habitats; Indicator species; Insect colonies; Insect ecology; Insect nests; Insects; Leaf cutting ants; Leaves; Plant populations; Plant species; Planting density; Plants; Rainforests; Seed germination; Seedlings; Species richness; Synecology; Terrestrial ecosystems
• ISSN: 0266-4674; 1469-7831
• DOI: 10.1017/S0266467412000259

Secondary forests promote an increased abundance of leaf-cutting ants (LCA) but the consequences on forest dynamics have been poorly addressed. Here we examine seedling assemblage attributes, seed germination and seedling survival across foraging zones of Atta cephalotes colonies inhabiting 15 second-growth patches (25–47 y old) of Atlantic forest. Seeds and seedlings were monitored within foraging zones and control sites over 1 y, including spots around ant nests. Overall, 1862 seedlings from 108 plant species were recorded. Seedling density decreased by 53% in foraging-zone plots (3.31 ± 0.23 seedlings m−2) when compared with control plots (7.02 ± 0.44 seedlings m−2) and a similar decrease was observed for species richness. Ant-induced alterations in the seedling assemblage were further indicated by segregation between foraging-zone and control plots (NMDS), habitat effects on species similarity (ANOSIM), and indicator tree species associated with control plots. While seed germination and seedling survivorship were uncorrelated to either nest distance or age of second-growth stands (with the exception of Tapirira guianensis), defoliation by LCAs was a significant cause of seedling mortality. Our results suggest that LCAs interfere with successional trajectories of Atlantic forest as foraging zones filter seedling establishment, supporting less-dense, impoverished and convergent seedling assemblages.