Spatial patterns of movement of dung beetle species in a tropical forest suggest a new trap spacing for dung beetle biodiversity studies

Variegated tropical landscapes conserve diverse dung beetle communities

BACKGROUND

Conserving biodiversity in tropical landscapes is a major challenge to scientists and conservationists. Current rates of deforestation, fragmentation, and land use intensification are producing variegated landscapes with undetermined values for the conservation of biological communities and ecosystem functioning. Here, we investigate the importance of tropical variegated landscapes to biodiversity conservation, using dung beetle as focal taxa.

METHODS

The study was carried out in 12 variegated landscapes where dung beetles were sampled using six pitfall traps, 30 m apart from each other, along a transect in each studied landscape use and cover classes-LUCC (forest fragment and corridor, coffee plantation, and pasture). We baited each pitfall trap with 30 g of human feces and left open for a 48 h period. We also measured three environmental variables reflecting structural differences among the studied classes: canopy cover, local vegetation heterogeneity and soil sand content.

RESULTS

We collected 52 species and 2,695 individuals of dung beetles. We observed significant differences in the mean species richness, abundance and biomass among classes, with forest fragments presenting the highest values, forest corridors and coffee plantations presenting intermediate values, and pastures the lowest values. Regarding community structure, we also found significant differences among classes. Canopy cover was the only variable explaining variation in dung beetle species richness, abundance, biomass, and community structure. The relative importance of spatial turnover was greater than nestedness-resultant component in all studied landscapes.

DISCUSSION

This study evaluated the ecological patterns of dung beetle communities in variegated tropical landscapes highlighting the importance of these landscapes for conservation of tropical biodiversity. However, we encourage variegation for the management of landscapes that have already been fragmented or as a complementary initiative of current conservation practices (e.g., protection of natural habitats and establishment of reserves).

The Importance of Maize Management on Dung Beetle Communities in Atlantic Forest Fragments

Dung beetle community structures changes due to the effects of destruction, fragmentation, isolation and decrease in tropical forest area, and therefore are considered ecological indicators. In order to assess the influence of type of maize cultivated and associated maize management on dung beetle communities in Atlantic Forest fragments surrounded by conventional and transgenic maize were evaluated 40 Atlantic Forest fragments of different sizes, 20 surrounded by GM maize and 20 surrounded by conventional maize, in February 2013 and 2014 in Southern Brazil. After applying a sampling protocol in each fragment (10 pitfall traps baited with human feces or carrion exposed for 48 h), a total of 3454 individuals from 44 species were captured: 1142 individuals from 38 species in GM maize surrounded fragments, and 2312 from 42 species in conventional maize surrounded fragments. Differences in dung beetle communities were found between GM and conventional maize communities. As expected for fragmented areas, the covariance analysis showed a greater species richness in larger fragments under both conditions; however species richness was greater in fragments surrounded by conventional maize. Dung beetle structure in the forest fragments was explained by environmental variables, fragment area, spatial distance and also type of maize (transgenic or conventional) associated with maize management techniques. In Southern Brazil’s scenario, the use of GM maize combined with associated agricultural management may be accelerating the loss of diversity in Atlantic Forest areas, and consequently, important ecosystem services provided by dung beetles may be lost.