n African Entomology - Arthropod assemblages associated with wild and cultivated indigenous proteas in the Grabouw area, Cape Floristic Region




Control of arthropod pests on indigenous flower crops often has particular challenges. Here we investigate the arthropod species associated with indigenous cultivated species and cultivars in the Cape Floristic Region (CFR), South Africa. Arthropod individuals were collected from various commercial varieties of protea as well as from wild protea plants. Arthropod individuals were recorded directly on plants in the field (for disturbance-sensitive species), as well as from specific plant parts carefully enclosed in plastic bags and taken to the laboratory. Of the arthropod morphospecies recorded, 95.9% were insects, and the rest mostly mites. A total of 37% of the individuals could be identified to species level, along with 33 new species records of arthropods on protea plants. Taxonomically, Coleoptera, Lepidoptera, Hymenoptera and Diptera were the most abundant and speciose groups. Structurally complex plants and mixed stands of plant species harboured the most arthropod species. Morphospecies were sorted into guilds, as determined by previous studies. In general, guild structure reflected the complexity of structure of individual plants as well as the mixture of plant species and cultivars, with apparently strong natural enemy activity on complex plants and mixed groups. The free-living, flower visitor guild was the most abundant, with largely beetles contributing to this guild. Endophages were about equal in abundance across all cultivars but less on those with simple structures. From rank abundance curves, a total of 30% of the arthropod species were categorized as abundant, with the rest (70%) being rare. Most species were generalists on the various proteas, with some being species or cultivar specialists. A total of 7.26% species recorded were major pests affecting commercial production of proteas in the CFR. This protea agroecosystem, being composed of plant types being grown in their general native area, resulted in about 93% of the arthropod species being restricted to the Proteaceae, with only 5.6% associated with other South African crops. Even though some of this arthropod assemblage is adverse for protea farming in theCFR, these commercial fields are nevertheless playing a role in biodiversity conservation in the fynbos. The wild proteas supported only intermediate arthropod abundance, suggesting strong, and probably complex, natural regulatory processes at work.


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