RESUMO
Naturally fragmented landscapes are adequate systems for evaluating patterns and mechanisms that determine species distribution without confounding effects of anthropogenic fragmentation and habitat loss. We aimed to evaluate an ant metacommunity's spatiotemporal patterns in montane forest islands amid a grassland-dominated matrix. We assessed these patterns by deconstructing the ant metacommunity into forest-dependent and habitat generalist species. We sampled twice a year (summer and winter) over 2 years (2014 and 2015), using soil and arboreal pitfall traps, in fourteen forest islands (varying in size, shape, and connectivity) in the Espinhaço Range Biosphere Reserve, Brazil. We evaluated the relationship between ant species richness, composition (ß-diversity), and predictor variables of forest island structure (canopy cover and understory density) and landscape structure (forest amount, number of forest islands, and shape). We sampled 99 ant species, 66.7% of which were classified as forest-dependent and 33.3% as habitat generalist species. We found that ant ß-diversity was higher in space than in time, and that species composition variation in time (temporal ß-diversity) differed between ant species groups. Both ant groups responded differently to forest island and landscape structure characteristics. Landscape structure seems to act as a spatial filter and the forest islands' local characteristics as an environmental filter, which jointly determine the local and regional diversity. We demonstrate the importance that forest archipelagos pose to ant metacommunity's structure and dynamics in montane tropical regions. Mountaintop conservation and management strategies must consider the forest island archipelago to maintain the biodiversity and the functioning of these systems.
Assuntos
Formigas , Animais , Biodiversidade , Ecossistema , Florestas , ÁrvoresRESUMO
Naturally fragmented landscapes provide suitable scenarios through which to investigate patch and landscape effects on biodiversity patterns in areas that are isolated from the disturbances usually associated with human-made fragments. We aimed to investigate the patch and landscape effects on the diversity of forest-dependent and matrix-tolerant dung beetles in a naturally fragmented landscape. We also assessed the influence that seasonal and vegetation variations had on these dung beetles. We sampled dung beetles during two summers and two winters in 14 forest islands of various sizes and shapes within a natural mountainous forest archipelago in southeast Brazil. We measured the patch and landscape variables based on high-resolution multispectral images of circular sectors with radii of 100, 250, and 500â¯m. We used generalized linear mixed models to relate dung beetle metrics to patch and landscape attributes. The interaction between canopy cover and season influenced both species' richness and abundance of the dung beetle metacommunity. The forest-dependent species' richness increased with greater canopy cover, regardless of the season. Patch attributes (e.g., size, canopy cover, distance to the closest patch, and distance to continuous forest) and landscape attributes (e.g., percentage of forest in the landscape, total edge, number of patches, distance to the nearest neighbor, and shape complexity) had small general effects on dung beetle species as a whole and on matrix-tolerant species in particular. However, these values strongly influenced forest-dependent species' richness, abundance, and temporal beta diversity. The matrix-tolerant species, therefore, mask the effects of patch and landscape effects on forest-dependent species within the mountainous forest archipelago. In other words, the changes in these patch and landscape attributes influenced forest-dependent and matrix-tolerant species differently. Therefore, the evaluation of entire metacommunities may not be helpful when evaluating species-specific responses in mixed landscapes-a fact that impairs the conservation of forest-dependent species.