Invertebrate diversity in response to the removal of alien invasive plants in the Luvuvhu river catchment: indications of recovery

Invertebrate diversity in response to the removal of alien invasive plants in the Luvuvhu river catchment: indications of recovery
Stefan H. FOORD, Rifilwe V. Modiba
Centre for Invasion Biology, Department of Zoology, University of Venda, Thohoyandou, 0950

Invasive alien plants (IAP’s) have considerable negative impacts on freshwater habitats. South Africa has implemented an innovative programme for the systematic removal of these plants aimed at, amongst other objectives, restoring biodiversity and ecosystem services in these threatened habitats. These restoration processes are expensive and have to be evidence-based. Few studies include invertebrates as indicators of efficacy of these interventions. In this study we use in-stream macroinvertebrate and adult Odonata assemblages as indicators of restoration success by quantifying the response of biodiversity metrics for these two groups to the removal of IAP’s in a strategic water resource of South Africa that is extensively invaded by IAP’s. The study consisted of a replicated design that included at least two cleared, invaded and uninvaded sites in the upper reaches of six sub-catchments of the Luvuvhu river catchment, Limpopo Province. Three metrics of water quality based on macro-invertebrates did not respond to clearing but the SASS5 total score responded positively to the number of times cleared. Although clearing only had a weak positive effect on adult odonate species richness it had a positive impact on DBI scores. These differences were mainly the result of significantly larger DBI scores in the cleared sites as compared to the invaded sites. Results suggest that water quality is positively impacted by repeated clearing pointing to the importance of follow up procedures after initial clearing. The adult odonate diversity as measured by richness, endemicity, threat and distribution, respond positively to all forms of clearing.