Jochen H. Bihn

Loss of functional diversity of ant assemblages in secondary tropical forests

Secondary forests and plantations increasingly dominate the tropical wooded landscape in place of primary forests. The expected reduction of biodiversity and its impact on ecological functions provided by these secondary forests are of major concern to society and ecologists. The potential effect of biodiversity loss on ecosystem functioning depends largely on the associated loss in the functional diversity of animal and plant assemblages, i.e., the degree of functional redundancy among species. However, the relationship between species and functional diversity is still poorly documented for most ecosystems. Here, we analyze how changes in the species diversity of ground-foraging ant assemblages translate into changes of functional diversity along a successional gradient of secondary forests in the Atlantic Forest of Brazil. Our analysis uses continuous measures of functional diversity and is based on four functional traits related to resource use of ants: body size, relative eye size, relative leg length, and trophic position. We find a strong relationship between species and functional diversity, independent of the functional traits used, with no evidence for saturation in this relationship. Recovery of species richness and diversity of ant assemblages in tropical secondary forests was accompanied by a proportional increase of functional richness and diversity of assemblages. Moreover, our results indicate that the increase in functional diversity along the successional gradient of secondary forests is primarily driven by rare species, which are functionally unique. The observed loss of both species and functional diversity in secondary forests offers no reason to believe that the ecological functions provided by secondary forests are buffered against species loss through functional redundancy.

Spectrum of Ants Associated with Araucaria angustifolia Trees and Their Relations to Hemipteran Trophobionts

The community of ants inhabiting Araucaria angustifolia trees or foraging on this conifer was studied in the rain forest reserve Pró-Mata on the Serra Geral of Rio Grande do Sul, southern Brazil. Ants of 44 species were recorded of which 23 were nesting on Araucaria trees. Data on their abundance and relationships to trophobionts are presented. Amongst the latter, Planococcus citri was by far the most common species. It was associated with ants of the genera Crematogaster, Solenopsis (Diplorhoptrum), Linepithema, Myrmelachista and Camponotus. The results are discussed under ecological and biogeographical aspects.