Investigating behavior and ecology of Aphaenogaster swammerdami (Formicidae) in selectively logged forest: 20 years later – a happy ant?

摘要

The impacts of logging have been widely studied at the community level, describing changes in species composition and richness, whereas the small-scale effects on behavior and ecology of single species have received less attention. We investigated whether the Malagasy wood ant Aphaenogaster swammerdami exhibits differences in colony density, colony size, and feeding ecology between three different sites within the Kirindy Forest (CNFEREF), a dry deciduous forest in central western Madagascar. Specifically, we compared undisturbed primary forest, a selectively logged area, and one site exposed to natural disturbance caused by an adjacent river. Transect surveys were used to record colony density as well as diameter of the mound as a predictor of colony size. Focal colonies were selected at all three sites to assess other aspects of colony size, i.e. the number and size of workers and the home range area. The feeding ecology of ants from all three sites was compared by using observational records on food quality and quantity, as well as stable isotope analyses of ant workers. We found that in selectively logged forest, colony density was lower and colony size larger than at the two other sites. Feeding behavior differed slightly, as colonies from selectively logged forest had a higher intake of animal food sources. Thus, we tentatively conclude that A. swammerdami, despite its opportunistic lifestyle, still exhibits responses to selective logging, which took place 20 years ago. Replicating these findings on a larger scale and determining the specific mechanisms leading to changes in lifestyle along disturbance gradients should be the focus of future studies.