Session 31: Invertebrate Conservation

According to the State of Rivers Report (2017-2018), 15% of South African rivers were considered in a good state, with little to no pristine rivers remaining. Human activities such as mining, agriculture, abstraction, forestry, and urban run-off directly impact freshwater systems. These threats are compounded by fluctuating water temperatures from climate change, leaving no system unimpacted by our actions. Macro-invertebrates in freshwater environments play a crucial role in ecosystem functioning, and yet many species remain undescribed in southern Africa. Many of these known and undescribed species face extinction with little to no direct legal protection, despite the poor ecological state of freshwater ecosystems. Therefore, this book serves as a field guide to the commonly encountered freshwater macroinvertebrates of southern Africa, which play a critical role in freshwater and terrestrial ecosystems and aid ecologists, fishermen, and enthusiasts in understanding these organisms. The book focuses on aquatic invertebrates and further includes several semi-aquatic and terrestrial invertebrates that may be encountered in the field. Most taxa in this guide are discussed at the family level, and identifications are limited to what is observable to the naked eye. Field practitioners generally identify specimens at the family level, and the identification to lower taxonomic levels (genus or species) often requires microscopic investigation that is not practical for field identification. There are introductory notes on the diversity, distribution, life cycle, and taxonomic placement of each family within the order. Dichotomous keys are not provided in this guide; however, distinguishing features between families are provided in the introduction to the family trees and discussed on each family page, providing additional insight into the identification of common freshwater macroinvertebrates. Some taxa were not included (e.g. Polycentropodidae, Ephemerythidae and Polychaeta) as collection was not possible before publication. Despite this, an overview of macroinvertebrates is presented in brief.

Climate variability and change threaten global biodiversity. Species distribution models are a tool that can be used to assess the potential impacts of climate change on species ranges. Syritta (Syrphidae: Eristalinae) occupy key niches and provides key ecosystem services such as pollination and nutrient cycling. There is little documentation on the distribution, vulnerability and conservation status of Afrotropical Syritta. The responses of Syritta to climate change are also unexplored. In this study, the known occurrence of two Syritta species and bioclimatic data were used as predictors for the analysis of core habitats and potential range shifts in species distributions within South Africa. The ensemble modelling approach based on two models and two future climate change scenarios under representative concentration pathways (RCP 6.0 and RCP 8.5) for two time frames (2050 and 2070) were applied. Three model algorithms (maximum entropy, random forest and generalized linear models) were used with three assessment matrices (TTS, AUC, COR) to identify the most important predictor variables. The analyses show a climate-driven range expansion and reduction in the distribution of the two Syritta species for both 2050 and 2070. We demonstrate that rainfall and temperature in the coldest months may influence the range limits in different ways. This study is a first step towards applying biodiversity models to support long-term monitoring, conservation decisions and planning with consideration of climate change impacts on Syritta species in South Africa. It is a contribution to the implementation of strategies to meet targets in Goal A of the biodiversity framework of the UN Convention on Biological diversity. We recommend a complementary analysis of spatial structures to emphasize or refute the importance of areas expected to face suitability decline within South Africa to inform potential conservation strategies for the Syritta. 

The Maloti-Drakensberg mountain range is part of the Great Escarpment, which is the edge of the interior plateau of southern Africa and a rich biodiversity hotspot with high levels of endemism. However, studies on aquatic invertebrate dynamics in this region have been limited. The region, being a strategic water source area, boasts one of the highest densities of standing water bodies in the form of rock pools and Afromontane tarns. The current study collected macroinvertebrates and assessed environmental parameters of 70 water bodies (between 1127–2972 masl) from Golden Gate Highlands National Park to the southern Drakensberg during the prolonged rainy season of March and April 2022. We hypothesised that the community composition between tarns and rockpools, as well as the biotic diversity, will be different, given the differences in their hydroperiod. Afromontane tarns macroinvertebrate assemblages were dominated by widespread taxa including aquatic beetles (Dytiscidae and Hydrophilidae), bugs (Notonectidae and Corixidae), and odonates larvae (Aeshnidae and Libelullidae). Comparatively, rock pools were dominated by large branchiopods, dipterans, and hydraenids beetles. As expected, Afromontane tarns had greater diversity compared to rock pools, but there was no significant difference, in terms of community assemblages, between tarns in different regions or altitudes. We conclude that macroinvertebrate assemblages, apart from hydroperiod and habitat complexity, were driven by the sampling period where high dominance of predatory taxa resulted in a reduction of diversity. Although the region had a prolonged rainy season, macroinvertebrates species composition, particularly temporary ponds specialists, was neither affected nor delayed.

Increased above-ground biomass linked to elevated atmospheric CO2 levels will result in a 20–61% increase in the woody cover of African savannas. Understanding how biodiversity responds to these changes will inform conservation initiatives. Here we model the response to spider diversity across an elevational transect across the Soutpansberg mountain range in Limpopo, South Africa, that includes four significant plant physiognomies: savanna, grasslands, forests, and thickets. Spiders were sampled using pitfall traps during the hot and dry (September) and hot and wet seasons (January) over six years. The responses of 461 assemblages (256 species) to habitat structure, temperature, soil, available habitat, aspect, and seasonality (humidity) were modelled using generalized linear mixed models for richness and abundance and model-based multivariate analysis for species composition. The best models included seasonality (humidity) and woody cover. Spider richness and abundance decreased with increased woody cover. Seventy-five per cent of pure and reliable indicator taxa associated with woody cover decreased in abundance as woody cover increased. Indicator taxa that increased with woody cover were generalist species with large global distributions that included an exotic species. The importance of maintaining open savannas through grazing and fire is highlighted by the large number of endemic and undescribed species associated with this biome and the lower diversity and threat of exotic spider invasions related to areas that experience woody thickening.

Ichnestoma dealbata is one of 11 new species described in a revision of the beetle subtribe Ichnestomatina. Adults of the subtribe are thought to emerge from underground after substantial summer rainfall events and to remain active for only a few days afterwards. Females are generally unable to fly, so populations tend to be locally endemic, with restricted distributions. Ichnestoma dealbata has been described from a single locality near Calitzdorp. This paper reports on the discovery of the species at a second locality in the Little Karoo and speculates on possible emergence cues. From 2008, ad hoc biodiversity observations were made on and around a biodiversity stewardship site near Oudtshoorn. Many of these observations were posted on the online citizen science platforms, the Virtual Museum (https://vmus.adu.org.za/) and iNaturalist (https://www.inaturalist.org/). Ichnestoma dealbata was first photographed on the Oudtshoorn site in 2019 and again in 2021. Identification of this and another beetle species known from one locality, were made on iNaturalist. In 2022, live I. dealbata individuals of both sexes were observed, and behavioural observations were made. Flying males, aggressive interactions between males, and copulation were seen hours after a localised, intense hailstorm. Four millimetres of rain were measured 200 m away from the emergence site however, a more significant rainfall event occurred further away in the catchment. This suggests that environmental cues other than rainfall amount can trigger emergence, and further research on this is required. Climate change predictions for the Little Karoo indicate a high probability of warming, but rainfall predictions have a high degree of uncertainty. Species such as I. dealbata, with life cycles reliant on the timing and intensity of specific weather events, lend themselves to climate change research. Citizen science has played a role in expanding our understanding of this little-known species, and further information on distribution and emergence could be obtained by increasing awareness through local groups such as farmers' associations and the Custodians of Rare and Endangered Wildflowers programme. However, the use of public online platforms to store records could increase the risk of illegal collection.