Browsing by Author "Colville, Jonathan"

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    The effects of heuweltjies and Microhodotermes viator (Isoptera: Hodotermitidae) on invertebrate assemblages and species turnover in the succulent Karoo, Western Cape
    (2014) Cornell, Gabriel Lyle; Picker, Mike; Colville, Jonathan
    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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    Monkey beetles on the beat: urban monkey beetles reveal opportunities for pollinator habitat management in a South African city
    (2022) Brom, Peta; Underhill, Leslie; Winter, Kevin; Colville, Jonathan
    Against a backdrop of global declines in pollinators, evidence suggests that some guilds thrive in urban landscapes and relatively small interventions can provide habitat support in otherwise inhospitable urban landscapes. Despite this knowledge, there is a paucity of research on urban pollinators in Africa. This gap is noteworthy because Africa is a megadiverse region and southern Africa has three global biodiversity hotspots. This thesis is a first step towards filling the Africa gap. Its ought to do so by investigating urban monkey beetles (Coleoptera: Scarabaeidae: Hopliini) in two ways. Firstly, it relates Hopliini community structure to urban environmental gradients and local habitat composition. This was achieved by using pan traps to sample pollinators at 145 sites during two austral spring seasons in greater Cape Town in 2018 and 2019. The findings are that there were three divergent responses to urban landscape dynamics. 1) Those which exploited the urban environment. 2) Those which did not respond to an urban intensity gradient, but did respond to flower‐richness, 3) Those which preferred larger, less disturbed sites at the edge of the city. Secondly, ways that the management of Public Open Space (POS) and road verges can better support the connectivity of habitats containing endemic geophytes and spring annuals were considered. These flower populations provide breeding and foraging resources to Hopliini and other pollinators. They are an especially important resource to the group who are unable to move through or exploit the urban environment without them (Group 2 above). A mowing suspension was investigated to determine how long the indigenous spring show would take to complete the reproductive cycle and reach seed set. The study took a phenological approach to estimating the duration of the suspension. The findings indicate that mowing should be suspended for spring geophyte patches from the first week of August until after the first week of November. The charismatic Baeometra uniflora can be used as an indicator species for when the season has concluded. Methods of strategic landscaping and interplanting are discussed, noting that the peak flowering season in spring is followed by a lesser abundant summer show.
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    Taxonomy and Life History of Gall Midges (Diptera, Cecidomyiidae) on Drosanthemum and Malephora (Aizoaceae) in South Africa
    (2021) Van Munster, Stephany; Dorchin, Netta; Colville, Jonathan; Hoffmann, John Hugh
    South Africa is known for its highly endemic and remarkably species-rich fauna and flora. The Greater Cape Floristic Region, consisting of the Cape Floristic Region and the Succulent Karoo Region, is home to South Africa's second most diverse plant family, the Aizoaceae. While the Aizoaceae are relatively well studied, there has been little work done on their associated insect fauna. Preliminary observations in recent years revealed a diverse community of gall midges on these plants. This study aimed to investigate the gall midges associated with two speciose genera of Aizoaceae and it is the first of its kind in South Africa. I report five new species of gall midges, three belonging to Asphondylia Loew and two to Lasioptera Meigen. These species are described from several species within the Aizoaceae genera Drosanthemum Schwantes and Malephora N.E.Br., and additional host records were recorded from Lampranthus N.E.Br., Carpobrotus N.E.br., Acrodon N.E.Br., Cephalophyllum Haw. and Jordaaniella H.E.K. Hartmann. The gall midges are described from adults, pupae and larvae and information is provided on their galls, life history and distribution. Morphological attributes of the gall midges support the description of five distinct species. Furthermore, morphological characters of the Lasioptera species described here do not fit entirely with those of the genus, suggesting that a new genus should be established for them. These results provide a mere snapshot of the gall midge diversity that is to be found on Aizoaceae in southern Africa, and much work is still to be done on the Cecidomyiidae of South Africa as a whole. Further targeted sampling may reveal greater distribution ranges and additional host plants for the five species described here, as well as many more undescribed species across the Aizoaceae.