Dung beetles as sensitive indicators of land use change and quantification of their ecosystem services in northern and central Vietnam
The conversion of tropical forests by anthropogenic land uses has generated a large variety of fragmented habitats, leading to changes in animal diversity. Dung beetles (DB) respond sensitively to both, changes in the composition of vertebrates whose excrements provide food and nesting material, as well as changes in the physical structure of their habitats. Changes in DB communities have been often described via the taxonomic identity, but difficulties in the delineation of DB species that are taxonomically difficult to determine and highly diverse, combined with fundamental changes in the taxonomic composition of DB communities between different biogeographical regions, have posed great challenges for the taxonomic identification and therefore hindered the generalization of results. Morphological traits of beetles instead directly reflect their environmental adaptations through natural selection across species borders, and may provide a more robust means to detect patterns of community change imposed by different land uses. The main objective of the dissertation was to examine the effects of the conversion of primary forests (1st Forests) to secondary forests (2nd Forests) and to meadows on DB communities of tropical karst ecosystems, and the consequences for key ecosystem functions, using both taxonomic identity and morphological trait based approaches. As the tropical karst ecosystems typically harbour unique flora and fauna, it was hypothesized that these ecosystems would also host unique DB communities with high potential of endemism, and accordingly may reveal particular patterns in responses to forest conversion. Further we hypothesized that changing environmental conditions would lead to morphological adaptations of DB, eventually measurable as distinct clusters of morphological traits. Finally, changes in DB morphological traits may affect dung removal rate, being an important ecosystem function. This dissertation started with quantification and comparison of the structure and community attributes (i.e. species richness, abundance and biomass) of DB between land use types in two spatially separated nature reserves (NR) in north eastern and north central Vietnam. Surprisingly, species composition and community structure differed remarkably between two NR. Clear patterns of responses of DB to forest conversion were found between forests and meadows, with meadows showing a higher abundance and species richness being compared to forests (Chapter 1) In Chapter 2, we successfully used the morphological trait based approach to identify and characterize three distinct morphological trait clusters reflecting DB adaptations to changing environmental conditions resulting from the forest conversion. Our results highlight the potential to further the use of morphological traits in examining anthropogenic impacts on community structure. In Chapter 2, we found that body length and body mass rather than abundance determined dung removal rate, but the large bodied DB were particularly vulnerable to forest conversion. Accordingly, the forest conversion by human land uses resulted in a loss of DB functioning and resulting their key ecosystem service, dung removal rate. Since large bodied DB play a vital role in ecosystem functions and were highly sensitive to forest conversion, it is critical to focus on the large DB species in conservation management. However, the poor understanding of the taxonomy of SE Asian DB is hindering conservation decisions, because reliable information on species composition, distribution and diversity is lacking. Therefore, in Chapter 3, we focussed on the taxonomy and distribution of the dominant and large bodied DB of the genus Copris by providing a species list for Vietnam with detailed illustrations and identification keys to all Vietnamese members, and with the worldwide distributions of all these species. Two new Copris species, one country records and rare species recorded from the karst ecosystems were also described and included in the key. In addition, the little known subgenus Copris (Paracopris) was reviewed along with description of a new species from Java (Indonesia) The genus Synapsis contains remarkably large bodied DB reaching a length of up to 52 mm (i.e. in S. tmolus Fischer, 1821) Since Synapsis spp. mainly occur in SE Asian tropical forests, they may be useful bio indicators for undisturbed forests. However, the species status of particular taxa has undergone repeated changes due to poorly defined species boundaries. In Chapter 4, we therefore presented a thoroughly illustrated key and diagnoses of all worldwide known Synapsis species based on morphological examinations of a great number of type specimens housed at European natural history museums. In addition, a new species and a rare species of the genus Synapsis recorded from the karst ecosystems were formally described.