Long-term equilibrium of tropical ant communities
David A. Donoso, David A. Donoso
Escuela Politécnica Nacional, Ecuador; Escuela Politécnica Nacional, Ecuador
Communities change with time. Studying long-term change in community structure permits deeper understanding of community dynamics, and allows us to forecast community responses to perturbations at local and global spatial scales. Here, the temporal dynamics of the Otongachi leaf litter ant community, occurring in a cloud forest in coastal Ecuador, were explored. By sampling this community 8 times over fifteen years, I assessed how the ant fauna caught by Winkler traps (more diverse and cryptic fauna) and caught by pitfall traps (larger, more mobile fauna) changed over time. The Otongachi leaf litter ant community was dynamic. Although species richness in the community remained constant, temporal turnover of species was high. Shifts in the rank abundance of species in the community were also large across the fifteen years and, on average, shifts in the rank abundance of species collected by Winkler traps doubled those occurring in pitfall traps from one census to the other. In spite of these trends, the Otongachi ant fauna showed no (Winkler) or weak (pitfall) evidence of directional change (towards a new community). Thus, this tropical ant community can be divided in two community compartments. The Winkler compartment composed by a more diverse and cryptic ant fauna appears to be resilient and stable in time. The pitfall compartment composed by larger and more mobile ants may be prone to respond to disturbance. This study suggests that species appearing/disappearing from a site may be rather the rule, difficult to separate from responses to ecological stress. Conclusions made in short-term studies, or studies comparing two (e.g. before and after) snapshots of a community, should thus be revisited. This study adds to the growing evidence that using ants as ecological indicators should incorporate long-term temporal dynamics.