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Stellenbosch University (2021)

The importance of heuweltjies for arthropod biodiversity in the succulent Karoo

Davids, Liaam

Titre : The importance of heuweltjies for arthropod biodiversity in the succulent Karoo

Auteur : Davids, Liaam

Université de soutenance : Stellenbosch University

Grade : Master Degrees (Conservation Ecology and Entomology) 2021

Résumé partiel
The Succulent Karoo biome of South Africa is home to unique patches of vegetation which are distinct from the surrounding homogenous matrix, locally known as heuweltjies. Heuweltjies are ubiquitous features of this landscape and support a variety of flora and fauna, however, whether and how they affect arthropod biodiversity in the landscape is poorly understood. Arthropods are vital for ecosystem functioning in resource limited environments. Therefore, understanding the importance of heuweltjies for arthropod biodiversity will allow us to better understand the role that heuweltjies play in conserving biodiversity and promoting landscape heterogeneity in this arid environment. The aims of this study were to determine whether heuweltjies promoted epigaeic (ground-dwelling) and foliage-dwelling arthropod abundance and diversity (measured as alpha- and beta-diversity) under drought conditions in the Prince Albert area, Western Cape, South Africa and how heuweltjie size, isolation and quality influenced this role. Both epigaeic and foliage-dwelling arthropod species richness and abundance were greater on heuweltjies than the surrounding matrix. Additionally, both heuweltjie and matrix plots contained distinct arthropod communities even at a relatively small spatial scale, within sites (25 -50 m) and between sites (1 – 20 km). Epigaeic arthropod assemblage differences were driven by species turnover (replacement of species) between the matrix and heuweltjie, whereas foliage-dwelling arthropod communities were driven by turnover and the differences in species richness (nestedness) with higher species richness found on the heuweltjies. This suggests that the heuweltjies are promoting arthropod diversity locally, most likely through the provision of habitat heterogeneity and additional niches

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