Red imported fire ants (Solenopsis invicta) and seasonality influence community refuge use

Abstract

Refuges are fundamental to animal ecology as refuge availability affects many levels of biological organization—from the behavior and physiology of individuals to the interspecific dynamics of a community. Although frequently studied in the context of predator–prey interactions, refuges may also mediate interspecific competition between native and invasive taxa given the role of refuges as a valuable resource. Because interspecific interactions (e.g., competition and predation) can be modulated by temporal and biotic (e.g., trophic level) factors, we used a manipulative approach to investigate community-wide refuge-use patterns in the context of two important ecological factors: invasive species and seasonality. We surveyed refuge (artificial cover object) use of ants and vertebrates in a forest community for 2 years, and we systematically suppressed an established invasive species (red imported fire ant, Solenopsis invicta) to examine its impact on community refuge use. Native Camponotus ants appeared to co-exist and share refuges with S. invicta, but we found evidence for a negative effect of S. invicta on vertebrate refuge use that was also influenced by season. Vertebrates were more abundant under refuges undergoing suppression of S. invicta, and they were less abundant under refuges during the fall (the season characterized by the highest occupancy of refuges by S. invicta). Thus, researchers must continue to examine the entire community and to incorporate the effects of season when assessing the impact of invasive species (e.g., at our site, a survey conducted only in the summer or only on native ants would have indicated a negligible effect of S. invicta on community refuge use).