oa African Entomology - Extrafloral nectaries of South African Proteaceae attract insects but do not reduce herbivory
Extrafloral nectaries are present on the leaves of several species of Proteaceae in the fynbos biome of South Africa, particularly in the genera Leucadendron R. Br., Leucospermum R. Br. and Mimetes Salisb. Ants (Hymenoptera: Formicidae) and other insects have been observed feeding at these nectaries. The numbers and diversity of insects on the leaves of Leucospermum conocarpodendron (L.) Buek and Mimetes fimbriifolius Salisb. ex J. Knight, species with extrafloral nectaries, were significantly higher than numbers of similar insects on the leaves of two Protea L. species that occurred in the same area, but which lacked extrafloral nectaries. The exclusion of ants from branches of Leucadendron laureolum (Lam.) Foure., L. conocarpodendron and M. fimbriifolius did not lead to increased levels of herbivory, as might be expected if these extrafloral nectaries function as attractants to ant-guards. In view of low ant numbers and levels of herbivory recorded in this study, we suggest that such a mutualism may still operate under different ecological conditions to those prevailing in our study. Alternatively, the nectaries may not reduce herbivory but could serve another ecological function.
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