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Research on Ants in the Cachoeira Nature Reserve

In its most general sense, my research seeks to elucidate the forces that shape and organize invertebrate communities. Research on the relationship between biological diversity and environmental change is directly applicable to conservation and provides a background against which human influence on the environment can be evaluated.

Journey to the ants

In particular, I have selected ants for the focus of my research. Ants are especially well-suited because they are dominant and conspicuous animals in the world’s terrestrial ecosystems. Ants are virtually everywhere, especially in the tropics, and it is actually almost impossible to find a single spot in a tropical forest without ants. Beside their high abundance they are also highly speciose. This is well manifested in tropical forests, where more than 100 ant species may coexists in just 20 sqm of leaf litter. Based on a common bauplan and eusocial organization, ants have evolved a wide range of life histories and morphological adaptations. In term of their foraging strategies and diets ants function at many levels in the ecosystem: as herbivores, detrivores, predators and predators of those predators. Among terrestrial invertebrates, ants are unsurpassed in the range of mutualistic interactions with other animals and plants. They also play a key role in the soil ecosystem as "ecosystem engineers" because of their soil moving activity and concentration of nutrients in and around their nests. Hence, ants present an obvious choice for biodiversity studies.

What determines biodiversity in a changing world?

Within the framework of the SOLOBIOMA project, my research focuses on the diversity of ants as a function of anthropogenic disturbance in secondary forests of the Mata Atlântica. As secondary forests are increasing in area throughout the tropics, the potential value of these secondary habitats for the conservation of biodiversity is increasing also. Consequently, the conservation and management of secondary forests will be a crucial factor to secure the future of biodiversity in tropical forests.

How can we measure biological diversity?

Biodiversity is the sum total of all biotic variation from the level of genes to ecosystems and can be measured in various ways. Each measure highlights different aspects of biodiversity and no single measure will always be appropriate. Existing knowledge about the effects of anthropogenic disturbance on pattern of biodiversity are based almost exclusively on measures of taxonomic diversity, i.e. numbers of species. However, other aspects of biological variety, namely morphological and ecological diversity, have received relatively litte attention in this context.

3 perspectives on biodiversity:

Taxonomic diversity of ant communities
Taxonomic diversity is the "classical" approach to biodiversity. In this part I study the impacts of human disturbance on species richness and species composition (alpha- and beta-diversity) of the soil and litter dwelling ant community. I do this by analyzing the ant community along an age gradient of naturally regenerating forest. Also, I study how different soil types modify the resistance and resilience of the ant community to anthropogenic alterations of the environment. The ultimate goal is to give sound advice on the value of secondary forest for the conservation of biodiversity in the Mata Atlântica of Brazil.
[PDF] Poster presented at IUSSI congress in Washington 2006

Morphological diversity of ant communities
Biological diversity can be quantified using various metrics that range from species counts to ecological and phyolgenetic diversity, each of which highlights a different aspect of biodiversity. Morphological diversity is one of the most intuitive measures of biological variety, and palaeontological studies have shown that temporal trends in morphological diversity are often poor predictors of taxonomic richness trends. However, for most groups of living organisms very little data exist on how species richness relates to morphological diversity. In my study I compare different aspects of the morphological structure of ant communities among secondary forests of various ages, e.g. size distribution and the morphospace of ant communities. The morphospace of an ant community is defined by some quantitative estimate of the empirical distribution of taxa in a multidimensional space that has axes that represent measures of morphology.

Ecological diversity of ant communities
Ecological diversity is still another view on biological variety. The complex relationship between taxonomic and functional diversity and key ecosystem processes has become a major research theme for the global science community. Natural communites differ greatly in the proportion of species performing different ecological functions. What determines such differences and how are these related to ecosystem functioning?
In terms of their diet ants spread out in a continuum between largely herbivorous and purely predacious taxa, with a high degree of omnivory. I am interested in changes of the trophic structure of ant communities (as one measure of ecological diversity) along a gradient of forest regeneration. For most taxa of ants information about their natural history including diet and ecological role in the food web are scarce. Direct observation of the nutrient acquisition of cryptic litter dwelling ants is hardly possible. Moreover, even in cases where direct observation is an option, it is critical to decide whether observations over restricted time periods are representative for the nutrient intake of a species in general. The analysis of the stable isotope composition of organisms provides an alternative approach. Isotopic signatures give an integrated insight into nutrient uptake over a lifetime of a focal organism. This technique will allow to track changes in the trophic composition of the ant community that come along with habitat modifications during forest succession.

This work is licensed under a Creative Commons License
page author: Jochen H. Bihn
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