Estabilidade temporal da comunidade de Scarabaeinae em fragmentos de floresta Atlântica

Abstract

The worldwide biomes are dominated by fragmented landscapes, what represents a great threat for biological diversity. We are in a race against time, searching for satisfactory information that allows a better comprehension of fragmented systems, with the purpose of finding conservation alternatives to minimize the biodiversity loss. The Atlantic Forest is an example of fragmented landscape, serving as a good model for the evaluation of forest fragmentation effects. Also, Atlantic Forest is considered a biodiversity hotspot and one of the most threatened tropical forests, what highlights the importance of studies in this Biome. Long term ecological researches are scarce, but extremely important to the understanding of the dynamics of forest fragments communities. Thus, the present study was carried out to investigate the response of Scarabaeinae dung beetle community to the Atlantic Forest fragmentation process both in short and long-term scale. The forest remnants were located in Viçosa, Minas Gerais, Brazil. Eighteen forest fragments, with different sizes and levels of isolation were sampled in the years of 1994, 1995, 1996 and 2010, using the same sampling design and sampling sites. The beetles were captured by pitfall traps baited with human feces or carcass. Richness was constant over time, but species composition showed high temporal changes. Larger and less isolated remnants always supported higher species richness and proved to be irreplaceable habitats for forest specialist dung beetles. The percentage of generalist species, on the contrary, was always higher in smaller and more isolated remnants. The fragmented system showed the same nested pattern over time, with smaller and more isolated fragments harboring a subset of the species found in the larger and richest remnants. Further, the communities found in the smaller fragments showed low temporal stability. When we tested whether immigration, extinction and turnover rates change with area and isolation of fragments in short and long term, we found that larger fragments exhibit the lower turnover and extinction rates in short term. However, in long term the dynamic of these fragments became similar to smaller fragments, with high extinction and turnover rates. Isolation only influenced the dung beetles immigration rates. The results obtained in this study show that the reduction of area and isolation are factors that negatively affect the community of Scarabaeinae; that Atlantic Forest fragmented landscapes are hyperdynamic and that even large fragments cannot support their richness in long term. Facing this reality, the conservation efforts should be directed towards larger remnants, since they sustain higher species richness and present higher temporal stability. Structural connectivity in landscapes is also an important aspect to be considered in the planning of conservation units, since it directly affects the movement rates of individuals in the landscape.