The effects of heuweltjies and Microhodotermes viator (Isoptera: Hodotermitidae) on invertebrate assemblages and species turnover in the succulent Karoo, Western Cape
Bachelor Thesis
2014
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University of Cape Town
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Abstract
Species turnover is a measure of a diversity that attempts to quantify the change in species composition along a spatial, temporal or environmental gradient. One such environmental gradient that has been shown to affect species turnover is local edaphic variation. This is seen in the Western Cape Province of South Africa, where the unique edaphic character of large earth mounds, known as heuweltjies, support distinct plant communities. The aim of this study is to assess whether these mounds, and the termite Microhodotermes viator commonly associated with them, also support distinct invertebrate communities, thereby contributing to invertebrate species turnover in the region. Pitfall and emergence traps were set on heuweltjies and in the surrounding matrix in the Karoo Desert National Botanical Gardens, Worcester, Western Cape Province. On- and off-mound community contrasts were assessed by means of a cluster analysis, and species turnover was measured using the Jaccard distance. Invertebrates were more abundant on the heuweltjies, which also had distinct communities when compared to the matrix. Spiders (Aranaea) were more abundant on the heuweltjies, as were in the invertebrates emerging from the frass, suggesting a trophic cascade. Invertebrates commonly associated with M. viator were found more commonly on the heuweltjies. The Jaccard distances indicated that environmental homogenisation of the heuweltjies resulted in homogenisation of the on-mound invertebrate communities. Heuweltjie soil enrichment was most similar to that of termite frass when compared to the matrix, supporting a termite origin for the heuweltjies.
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Cornell, G. 2014. The effects of heuweltjies and Microhodotermes viator (Isoptera: Hodotermitidae) on invertebrate assemblages and species turnover in the succulent Karoo, Western Cape. University of Cape Town.