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Accueil du site → Doctorat → Afrique du Sud → 2020 → The relative importance of species richness and functional diversity for ecosystem functions performed by dung beetles (Coleoptera : Scarabaeidae) in South Africa.

Stellenbosch University (2020)

The relative importance of species richness and functional diversity for ecosystem functions performed by dung beetles (Coleoptera : Scarabaeidae) in South Africa.

Simba, Lavhelesani Dembe

Titre : The relative importance of species richness and functional diversity for ecosystem functions performed by dung beetles (Coleoptera : Scarabaeidae) in South Africa.

Auteur : Simba, Lavhelesani Dembe

Université de soutenance : Stellenbosch University

Grade : Doctoral Degrees (Conservation Ecology and Entomology) 2020

Résumé partiel
The ongoing and accelerating loss of biodiversity due to anthropogenic activities has highlighted the effects of declining biodiversity on ecosystem functioning. In rangelands, livestock grazing along with variation in soil texture and climatic conditions can have significant impacts of biodiversity through alteration of habitat structure. In the semi-arid Karoo, South Africa, rangelands are extensive, and much of this ecosystem has been disturbed by livestock. This study aimed to determine how variation in land use (rangeland for livestock or protected area) and rainfall (100 to 520 mm.year-1 in the Nama Karoo and 20 to 290 mm.year-1 in the Succulent Karoo) influence the functionally important dung beetle diversity (i.e. species richness, abundance, functional diversity and body size, and their assemblage composition, and the ecosystem functions they provide in the semi-arid Karoo. Here, I investigate the relative importance of long-term (mean annual precipitation), medium-term (yearly difference from mean) and short-term (recent rains) on dung beetle species richness, abundance and assemblage composition. First, I assessed whether variation in land use, herbivore stocking rates, vegetation cover, soil texture and rainfall affect dung beetle communities and functional diversity. Dung beetle abundance and functional diversity showed contrasting responses between protected areas (PAs) and livestock farms, with PAs having a significantly greater abundance of dung beetles and lower functional diversity. Neither species richness nor body size was influenced by land use, although richness and abundance increased with higher herbivore stocking rates and rainfall. Species richness was best predicted by short-term rainfall and abundance by long-term rainfall. I further assessed whether variation in land use and rainfall affect dung beetle community composition. Dung beetle species composition varied between farms and PAs, and also varied with MAP, stocking rates, vegetation cover and rainfall season. I Identified 15 indicator species that explained this variation in dung beetle species composition which were associated with the different environmental variables, furthermore, four of these species were associated with two environmental variables. The response of dung beetle species to environmental variables was influenced by their functional traits, particularly reproduction capacity and dispersal ability. There was greater reproduction capacity for dung beetles in the PAs than on farms. Greater dispersal ability was also associated with PAs as well as the summer rainfall region and greater vegetation cover.

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