It has often been suggested that South Africa’s Cape fynbos shrublands, although
extremely rich in plant species, are poor in insects, thus representing a notable exception from the broad plant–insect diversity relationship. The aims of this study were to compare the diversity patterns of plant-inhabiting insects in fynbos and the vegetation of three neighbouring biomes (grassland, subtropical thicket, and Nama-karoo), and to test for a general relationship between plant diversity and insect diversity across these biomes.
South-western to south-eastern South Africa.
We conducted seasonal plant surveys and sweep insect sampling in 10×10 m plots in the Baviaanskloof Conservation Area (Eastern Cape), where all four biomes occur. We also conducted once-only collections in the core area of each biome.
Fynbos plots had insect diversity values similar to those of grassland and subtropical thicket (a dense, evergreen and spinescent shrubland with a high abundance of succulents and climbers), and significantly higher than Nama-karoo (an open, semiarid shrubland). A remarkably strong positive relationship was found between plant and insect species richness.
Previous generalizations were based on a few insect groups (e.g. butterflies, under-represented in fynbos), but ignored published results on other groups (e.g. galling insects, which are in fact over-represented in this vegetation). We show that, overall, insect diversity in fynbos is comparable to that of neighbouring biomes. Fynbos vegetation does not represent a significant exception from the broad positive relationship between plant diversity and insect diversity.||en