José H. Schoereder

The arboreal ant community visiting extrafloral nectaries in the Neotropical cerrado savanna

The cerrado savanna of Brazil embraces an area of approximately 2 million km 2 , in which vegetation physiognomies may vary from open grassland to forest with a discontinuous herbaceous layer. Here we describe the main ecological factors accounting for the prevalence of ants on cerrado foliage, and present a general characterization of the arboreal ant fauna of this savanna. The high incidence of ants on cerrado foliage results mostly from the wide occurrence of predictable liquid food sources in the form of extrafloral nectaries (EFNs) and insect honeydew, which act as efficient promoters of ant activity on vegetation. In addition, stem galleries and cavities constructed by boring beetles and insect galls create a nesting space frequently used by arboreal ants. Specific studies involving ants, herbivores and plants are reported to demonstrate the impact that foliage-dwelling ants can have on phytophagous insects, herbivory levels, and ultimately on host plants. These studies show that: (i) ants visit EFNs and likely benefit from this resource; (ii) EFN-gathering ants can benefit particular plant species by reducing herbivory and increasing plant fitness; (iii) presence of EFNs does not affect ant species richness within a given tree; (iv) there is not a particular ant species composition typical of plants with EFNs; (v) although plants with EFNs are visited by more ant individuals than non-nectariferous plants, this visitation pattern does not translate into lower numbers of herbivores on the nectariferous plant community. We suggest some promising research avenues to elucidate how community-level parameters can be tied to the ecology of ant-plant associations in cerrado.

Biodiversity and Ecosystem Functioning: a Conceptual Model of Leaf Litter Decomposition

In this chapter we present a brief history of studies on the relationship between biodiversity and ecosystem functioning (BEF), describing the main models used to explain this relationship, as well as the biodiversity metrics most commonly used. Furthermore, we use litter decom‐ position as a process model, presenting a flowchart of mechanisms that may affect the decomposition. The flowchart represents the linking between the diversity of leaves that compose the litter, which is usually called the litter mixture, to its decomposition rates. Finally, we present a simplified flowchart of the edaphic trophic web, relating it to litter decomposition, and some perspectives for future studies in this area.

Biodiversity and Ecosystem Functioning in Tropical Habitats — Case Studies and Future Perspectives in Atlantic Rainforest and Cerrado Landscapes

Currently, environmental changes can be seen as an intrinsic feature of ecosystems, once finding ecosystems that do not suffer of anthropogenic pressures, either direct or indirect, is rare [1]. Such pressures come from the continuous and exponential human population growth, which propels urbanization, activities and processes directly linked to the use of fossil fuels, mining, agriculture and cattle growth. The maintenance of current human population growth implies in the supply of a huge demand for food and technology, resulting in rising pollution and loss of habitats and entire ecosystems [2-5].