Masters Degrees (Conservation Ecology and Entomology)

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Browsing Masters Degrees (Conservation Ecology and Entomology) by Author "Benade, P. C."

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    Invaded range and competitive ability of the newly invasive Polistes dominula compared to that of its native congener species in the Western Cape, South Africa
    (Stellenbosch : Stellenbosch University, 2016-03) Benade, P. C.; Roets, F.; Veldtman, Ruan; Samways, Michael J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: The European paper wasp Polistes dominula (Christ)(Hymenoptera: Vespidae: Polistinae) established itself as a prolific invader across the globe and has been recorded and studied on all continents, except those with extremely low temperatures. In the invaded ranges it can displace native wasp species. This invader was first recorded in the Western Cape Province of South Africa in 2008 with little subsequent attention given to it after this initial record. In 2012 it was recorded in Stellenbosch, some 28 kilometres from where it was first seen. It is now fairly common in the region which prompted investigations into its ecology and effect on native biodiversity. In this study the current invaded range and habitat preferences of P. dominula in the Western Cape of South Africa was determined. It was found to have increased its range into numerous towns within the Western Cape Province. However, P. dominula seemed for the most part to be confined to the Cape Metropolitan area. The Cape Fold Mountain belt to the east and Atlantic Ocean to the west apparently creating a hinderance to its dispersal. Even so, P. dominula was later also found outside of this area with human mediated distribution thought to be the main driving factor. This because, as demonstrated in this study, P. dominula prefer human altered environments. To successfully invade and persist in a new range, P. dominula may possess a few advantageous characteristics over native species including release from enemies, greater colony productivity, longer activity season and a smaller body size. Here I investigated these factors by comparing P. dominula and the South African native congener species Polistes marginalis where these occur in sympatry. Over a period of 12 months (June 2013 to July 2014) foraging wasp activity of both species was recorded and compared. At the onset of winter and when wasp activity ceased, nests from both species were collected in order to determine enemy release, colony productivity and body size. Activity of the invasive P. dominula started earlier than the native P. marginalis allowing it to have greater abundance than the native species at the onset of P. marginalis activity. Nests of P. dominula also contained more cells than that of P. marginalis denoting greater colony productivity. Body size was not found to be significantly different to that of the native and therefore was not deemed to give P. dominula any advantage. Suprisingly, P. dominula had a greater paratisation rate than that P. marginalis, refuting predictions under the enemy release hypothesis. Polistes dominula is a prolific invader of newly acquired ranges in South Africa. It has already surpassed the natural barrier that once was the Cape Fold Moutain Range and the possibility exists that it could now invade more inland locations towards the east. It also outperforms the native species on several aspects that may lead to an ability to outcompete native congener species. Its effect on native arthropod taxa that forms part of its diet and on plant pollination has yet to be determined, but all evidence suggests that this species should be controlled as much as possible in order to prevent negative impacts on native biodiversity. These programmes should be focussed in urban areas where these wasps proliferate.