1. Increased emphasis is being placed on developing effective biodiversity conservation tools for practical conservation planning. The microfilter is such a biodiversity planning tool but has yet to be fully explored to appreciate its effectiveness. The key premise of the microfilter is that ecosystems contain certain physical elements that are specifically associated with a diversity of species. Identifying such microfilters could therefore complement existing conservation planning tools such as coarse and fine filters.
2. To explore the value of the mesofilter as an operational scale in conservation planning, we studied 18 remnant patches of endangered montane grassland in KwaZulu-Natal, South Africa, using the physical landscape feature of patch rockiness as an abiotic surrogate for biodiversity. The objective was to determine whether the mesofilter of rockiness can predict variation in species richness and composition for three dominant grassland taxa (plants, butterflies, and grasshoppers) at the landscape scale.
3. Variable levels of rockiness had significant interactions with all three focal taxa. Higher species richness of all taxa was closely associated with higher levels of rockiness in a patch. The rocky mesofilter only predicted significant differences in species composition for butterflies. Elevation was also important, possibly another mesofilter for plants and grasshoppers in this landscape.
4. Synthesis and applications. The results indicate that the use of an abiotic surrogate such as rockiness can predict biodiversity value across multiple taxa. The mesofilter is therefore a valuable surrogacy and congruency tool for practical biodiversity conservation across this landscape and would likely have similar value if explored elsewhere. It also has value in the design and management of protected areas.
