Plant characteristics determine insect borer assemblages on Protea species in the Cape Fynbos, and importance for conservation management

Abstract

The influence of regional climate, biotope and host-plant variables on the frequency of occurrence of insect borers associated with infructescences of Protea species in the species-rich flora of the Cape Fynbos was investigated. Large samples of infructescences (n = 1000) were collected on a seasonal basis and borers identified and quantified. Data were analysed using DECORANA and CANOCO so as to correlate environmental variables with borer occurrence. Distinct differences in frequency of occurrence of the various insect taxa were recorded on the various plant species studied. These differences were primarily accounted for by physical host-plant characteristics (infructescence and seed set variables), and secondarily, by biotope variables and climatic factors. Fynbos plant characteristics therefore play a major role in determining insect abundance. Plant diversity in the Fynbos is maintained by burning. These management burns, however, should not be applied too frequently or over areas large enough to extirpate any borer species. As these borers are excellent umbrellas for many other insects, their conservation covers Fynbos insect diversity in general.