Conservation of diverse parasitoid assemblages across agricultural mosaics within the Cape Floristic Region, South Africa

[摘要] ENGLISH ABSTRACT: The ever-growing agricultural industry within the Cape Floristic Region (CFR) threatens many arthropod species, including functionally beneficial insects such as parasitoids. Damage caused by insect pests within agricultural landscapes may be reduced by these important natural enemies. Various other vital ecosystem services and functions may be provided by maintaining structurally diverse agricultural landscapes as habitat heterogeneity promotes biodiversity. Here, I aim to investigate changes in parasitoid assemblages between various biotopes and across seasons within the CFR winelands.Firstly, I assess whether parasitoid richness and assemblage structure differs between five dominant biotope types within CFR agricultural mosaics. I also investigate which environmental variables influence changes in diversity. The biotopes were vineyards, old fields, riparian vegetation, remnant natural vegetation, and areas invaded by alien trees. I found that parasitoid assemblage structure differed significantly among all biotopes, with the undisturbed habitats supporting highest parasitoid diversity. Each biotope type made a unique contribution to overall parasitoid diversity. Structural diversity and botanical diversity, as well as the amount of untransformed habitat in the landscape, influenced parasitoids. Various spatial scales are therefore important when conserving these organisms. By maintaining a diversity of biotope types, farmers will be able to promote parasitoid biodiversity across farmland mosaics.Secondly, I assess the changing parasitoid assemblage structure and diversity across these biotope types over three seasons. Sample seasons were autumn, spring and summer. I found that parasitoid assemblage structure differed between the biotope types across the three seasons, with different biotopes having differential importance between seasons. Spatial and temporal turnover of species therefore takes place across agricultural landscapes in response to changing environmental conditions across various seasons.It is therefore necessary for farmers to preserve a variety of biotope types to promote species movement and re-establishment throughout farmland mosaics. To conserve these functionally important insects, we need to consider movement of parasitoids throughout landscapes, and over larger spatial and temporal time-scales. Here I show that habitat heterogeneity is an important consideration for future farmland design and planning for human-induced disturbances.

[发布机构] Stellenbosch University