Patterns of ant activity and nesting ecology depend on flooding intensity in a Neotropical floodplain

Abstract

Disturbance shapes ecological communities. Frequency, predictability, and intensity characterize disturbances, which select for resistant and/or resilient traits of species. Unpredictable and infrequent disturbance events, especially those with no reliable cues, lack selection strength and have less calculable effects on species assemblages and trait-based species sorting. In a flood plain in Northeast Costa Rica, across sites with varying flood frequency and no reliable cues to signal flooding, we used ants as a focal taxon to assess the impact of disturbance on ant activity and species assemblage. We examined activity patterns such as extent of occupancy of baits and nesting guild (i.e. strata used) that might mediate the effects of stochastic flood events. We hypothesized that the ant community in the most frequently flooded site would be dominated by above-ground nesting ants whose nesting traits make them resilient to inundation. The site with the most frequent flooding had the lowest level of ant presence on baits and differed in species assemblage, as demonstrated by the analysis of similarity, compared with the sites with lower flooding frequency. Neither overall species richness nor richness of species in the above-ground nesting guild differed between sites. However, nesting in trees above flood waters may be beneficial to escape frequent and unreliable flooding of habitats, and, as we hypothesized, there was greater activity of above-ground nesting ants compared with ground nesting ants in the most frequently flooded site. These differences in nesting guilds were diminished in the drier sites.