A Descriptive Study of wetland vegetation, ecology, habitat and Rift Valley Fever virus vectors in South Africa.

Brand, R. F.; Rostal, M.; Kemp, A.; de Jager, L.; Zwiegers, H.; van Staden, L.; van Huyssteen, C.; Anyamba, A.; Gregory, N.; Cordel, C.; Karesh, W.; Paweska, J. T.; Gqalaqha, Z. T.

doi:10.1101/2025.08.13.670234

bioRxiv · 10.1101/2025.08.13.670234

A Descriptive Study of wetland vegetation, ecology, habitat and Rift Valley Fever virus vectors in South Africa.

Brand, R. F.·Rostal, M.·Kemp, A.·de Jager, L.·Zwiegers, H.·van Staden, L.·van Huyssteen, C.·Anyamba, A.·Gregory, N.·Cordel, C.·Karesh, W.·Paweska, J. T.·Gqalaqha, Z. T.

View original source ↗Export metadata ↓

Abstract

Outbreaks of Rift Valley fever (RVF) have been closely linked to environmental conditions that support large vector populations with what is required for breeding of vectors. Fine-scale vegetation surveys were used to assess how wetland plant communities vary across sites with historical RVF outbreaks in Free State Province of South Africa and to detail plant species density that correlates with mosquito habitat. MethodsAt 22 sites, we compiled 201 releves using the modified Braun-Blanquet method in combination with 200 transects using the line-point method developed specifically for this study. A total of 195 plants were identified and vouchered. These data were combined with soil analyses carried out at all 22 sites and with data from bimonthly mosquito trapping at all sites. Results and significanceWe identified an increase of invasive plants and upland species compared to the earlier study and observed that drought causes a change in wetland vegetation community structure and species composition. However, the wetland vegetation was still dominated by grasses and sedges, with a limited presence of Juncus and forbs. Livestock grazing pressure on wetlands to the drought results in reduced vegetation cover, abundance and diversity. Our work describes a changing landscape that may impact RVFV maintenance and transmission, and provides insights into extensive livestock farming and rainfall over shallow endorheic depressions in temperate grasslands and subtropical riparian environments.

Explore related subjects

ecology Preprint

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Brand, R. F., Rostal, M., Kemp, A., de Jager, L., Zwiegers, H., van Staden, L., van Huyssteen, C., Anyamba, A., Gregory, N., Cordel, C., Karesh, W., Paweska, J. T., Gqalaqha, Z. T.. 2025-08-16. A Descriptive Study of wetland vegetation, ecology, habitat and Rift Valley Fever virus vectors in South Africa.. https://doi.org/10.1101/2025.08.13.670234

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Species-composition distributions under competition, ecological drift and immigration

Understanding how species interactions, ecological drift, and immigration jointly shape community composition is a central goal of community ecology. These processes determine not only average community composition, but also how often different community states occur. Here, we ask how competition reshapes the neutral distribution of community composition generated by drift and immigration. We analyze a stochastic two-species competition model with immigration and derive the stationary distribution of relative species composition near neutrality. The stationary distribution shows when communities are usually balanced and when they are instead dominated by one species. Species dominance can become common even when the corresponding deterministic model predicts stable coexistence, particularly in smaller communities. Balanced and dominance states can also occur together, producing a trimodal distribution. Competitive asymmetry further biases the distribution toward the competitively favored species. Thus, the interplay between competition, ecological drift, and immigration determines not only how much community composition varies, but also which community states are most likely to be observed. Our results provide an analytical bridge between neutral and competition theory and a framework for interpreting variation in community composition.

ecology↗

bioRxiv2026

Floristic composition, phenology, and conservation value of four peat bogs in Bucovina, with the presence of Betula nana

This paper presents a comparative analysis of the floristic composition and site characteristics of four peat bogs in Bucovina, Romania: Poiana Stampei, Romanesti, Saru Dornei, and Gaina-Lucina. The research was based on phytosociological releves on 25 msq plots and direct field phenological observations, on six field visits from May to August 2026. Vegetation was characterised using the Braun Blanquet method, and floristic similarity between sites was assessed with the Sorensen and Bray Curtis indices. All four plots shared a common core of taxa characteristic of peatland vegetation: Sphagnum spp., Carex rostrata, Drosera rotundifolia, Eriophorum vaginatum, and Vaccinium species. Species richness was 13 taxa at Poiana Stampei, Romanesti, and Saru Dornei, and 12 at Gaina-Lucina. Romanesti and Saru Dornei showed the highest floristic similarity (descriptive values, not statistically tested, given a single releve per site), while Gaina-Lucina differed most markedly, not through species richness, which was similar across sites, but through species identity and through the presence of Betula nana, a glacial relict absent from the other sites. The results provide a descriptive basis for future research on the floristic composition and conservation of these habitats.

ecology↗

bioRxiv2026

Long-Term Surveillance Reveals Establishment of Aedes albopictus in Eastern Nebraska, USA

Aedes albopictus (Skuse), the Asian tiger mosquito, is a highly competent arboviral vector whose range has expanded substantially across the United States over the past four decades. Despite predictive models placing Nebraska within the species' climatically suitable range, its establishment status in the state has remained poorly characterized. Here, we report results from a nine-year mosquito surveillance program (2017-2025) conducted across 44 Nebraska counties in collaboration with the Nebraska Department of Health and Human Services. Ae. albopictus was detected in five counties, with sustained, annually increasing populations documented in Richardson, Douglas, and Lancaster counties. Richardson County recorded continuous detections during 2017-2025, with proportional representation rising to 60.50% of collected mosquitoes by 2025. In Douglas and Lancaster counties, temporal advancement of first seasonal detection in 2024 and 2025 provide evidence consistent with successful overwintering rather than annual reintroduction. A cumulative degree-day model predicted adult emergence in mid-May across all county-year combinations, consistently preceding trap deployment by two to seven weeks and revealing a systematic early-season surveillance gap. Generalized linear mixed-effects models indicated that trap-level detection persistence, rather than urban location, was the primary predictor of yearly Ae. albopictus positivity, suggesting that current invasion dynamics are driven by focal source populations. These findings provide strong evidence for the establishment of Ae. albopictus in eastern Nebraska and highlight the need for earlier seasonal surveillance and standardized criteria to define establishment in northward-expanding vector populations.

ecology↗