Investigating the impact of pompom weed (Campuloclinium macrocephalum) on invertebrate diversity in the grasslands of Gauteng.

In South Africa, the grassland biome is being invaded by a South American herb, commonly known as pompom weed (Campuloclinium macrocephalum). Changes in the natural grassland vegetation are likely to affect the native invertebrate assemblages, but to date it remains unknown how pompom weed affects invertebrate diversity. To quantify this effect, we compared Coleoptera (beetle) and Cicadellidae (leafhopper) assemblages between uninvaded and invaded treatments, as well as the beetle assemblage seperately, divided into canopy-dwelling and ground-dwelling beetles, using unbaited pitfall traps and sweepnet sampling. Specimens were identified to species level and it was shown that the beetle assemblage had a higher species richness in uninvaded sites, but an elevated abundance of certain species in the invaded sites. In contrast, the leafhopper assemblage had a higher species richness in the invaded sites and a four times higher abundance in the uninvaded sites. Ground-dwelling beetles did not show any difference in species richness or abundance between treatments, but canopy-dwelling beetles once again had a higher richness in uninvaded sites and an inflated abundance in the invaded sites. Ordinations showed that invertebrate assemblage compositions asssociated with each treatment were different for all the assemblages studied except the ground-dwelling beetles. Although pompom weed appears to be an attractive resource habitat for certain native invertebrates, some species might be lost if grassland habitats continue to be invaded by pompom weed.