Edge effect and species–area relationships in the gall-forming insect fauna of natural forest patches in the Brazilian Pantanal
The aim of this study was to (i) measure differences in species richness between edge habitats versus interior habitats, or more precisely the edge effect, and (ii) test the species–area relationship for gall-forming insects in natural forest patches in a Brazilian floodplain (Pantanal of Mato Grosso do Sul). These patches are regionally known as ‘capões’, basically composed of woody vegetation. Twenty-seven patches were surveyed. In each patch two transects were conducted for gall sampling. One transect encircled the patches while the other was conducted in the interior of the patch, totaling 54 h of sampling. Host plant and galling insect species composition differed quite characteristically between the edge and the interior of patches, but galling insect richness did not. When insect gall richness was expressed as the ratio between insect gall and host plant richness (gall per plant ratio), a weak species–area relationship was found. Our results suggest that the number of galling insects per individual plant is not affected by the size of the patch. Despite these results, the natural forest patches found in this region seem well suited for long-term studies addressing species–area relationships. With regard to herbivorous insects, these studies should be combined with research on host plant dynamics during flooding and dry seasons.