Reassembly of ground-dwelling ant communities in reforestation plots in SW Costa Rica

Abstract

Abstract Due to agriculture and logging Costa Rica has lost many primary forests, making reforestation an important task. In order to judge the progress of reforestation it is important to follow the re-assembly of organismal communitiess within the restored habitats. The COBIGA project near La Gamba, in the Golfo Dulce region of Costa Rica, aims at reforestation of lowland sites with native tree species. Ants, as ubiquitous and highly abundant terrestrial organisms, have a substantial influence on tropical ecosystems. Their multiple roles include scavenging, predation, herbivory, and mutualistic interactions. We examined ant community responses, aiming to reveal the status of community regeneration and functional integrity. We compared the composition and diversity of ant assemblages at reforestation sites of three different ages (two, eight and ten years old) with an old-growth forest as a reference site. Offering canned tuna fish on ground level along replicated transects, we altogether observed 43 ant species representing six functional groups during two months of sampling. Most observed ant species were omnivorous but old-growth forest harbored a substantial number of other functional groups like generalized predators, arboreal predators, and arboreal omnivores. In contrast, the youngest reforestation site harboured a severely impoverished ant assemblage comprising mostly generalized polygynous and polydomous ant species from lower trophic levels. Within-site heterogeneity of ant assemblages increased from the youngest to the oldest forest. On top of that, our results show the importance of monitoring the progress of forest recovery to avoid the spread of invasive species into primary habitats.