A genetic investigation of the native stem-galling Tetramesa Walker (Hymenoptera: Eurytomidae) in South Africa, and their potential use as biological control agents
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The Tetramesa genus (Hymenoptera: Eurytomidae) comprises at least 200 species that feed exclusively on grasses. The highly host-specific behaviour of these wasps, and the damage that they can cause to their host plants, makes them ideal biological control agent candidates for invasive grasses. Very little is known about the Afrotropical Hymenoptera in general, and to date, almost all of the sampling effort in collecting and describing Tetramesa species has taken place in the Northern Hemisphere. Only four African species have been described; none of which are from South Africa. The Centre for Biological Control (CBC) at Rhodes University has been investigating biological control options for several African grasses that have become invasive in Australia and the Americas, and have been collecting Tetramesa specimens across South Africa since 2017. The insect communities associated with more than 55 different native grasses have been surveyed over this period. The uniform morphology of adult and larval Tetramesa has, however, made it impossible to determine whether these wasps are a single polyphagous species, or multiple oligophagous and/or monophagous species. We are currently using genetic barcoding tools (mitochondrial COI and nuclear ITS2 regions) and species delimitation methods to solve this problem. Our preliminary results have identified at least four putative species (or rather ‘molecular operational taxonomic units’ (MOTUs)). These were collected from single host plants, confirming their host-specificity and potential as biological control agents. It is likely that we will uncover many more undescribed species in the region as our sampling effort escalates.
Citation: van Steenderen, C.J.M., Paterson, I.D., Sutton, G.F., and Canavan, K. 2021. A genetic investigation of the native stem-galling Tetramesa Walker (Hymenoptera: Eurytomidae) in South Africa, and their potential use as biological control agents. Virtual presentation, 22nd Hybrid Congress of the Entomological Society of Southern Africa (28 June - 1 July 2021), Tshepise Forever Resort, Limpopo, South Africa.