Page 103 - University of Pretoria RESEARCH REVIEW 2016
P. 103

As global temperatures rise, the
threat of invasive insect species is expected to increase as insects expand their range into temperate areas.
In this context, the ability of flies
to withstand desiccation is likely to contribute to their invasive potential.
Dr Chris Weldon leads a research group in the Department of Zoology and Entomology, dedicated to the study of flies of economic significance – the FliES research group. He and his team work on
the behaviour, ecology and physiology of diverse
fly species, including fruit flies, blow flies and mosquitoes, among others. Their objective is to optimise the management of flies by understanding their biology.
Mediterranean fruit fly, Ceratitis capitata.
    His recent research has addressed how three pest fruit fly species cope with dry conditions. He found that the Mediterranean fruit fly, a species from Africa but now a global pest of fruit production, is highly resistant to desiccation due to low water loss rates and the ability to release water by breaking down fats stored in its body. The marula fruit fly, Ceratitis cosyra, which develops in marulas but is also a major pest of mango production, was also highly resistant to water loss, but its distribution is limited by the availability of its fruit hosts. The Natal fly, Ceratitis rosa, is not particularly resistant to desiccation and suffers high rates of water loss during dry, warm conditions, which explains its restricted distribution to humid coastal regions. These results suggest that C. capitata and C. cosyra are unlikely to be greatly affected by the warming, drying conditions expected in southern Africa as a result of climate change.
A recently discovered new fruit fly species, the Oriental fruit fly (Bactrocera dorsalis), was first detected in Kenya and has now spread through most of sub-Saharan Africa. Its presence is particularly alarming because it targets fruits as well as vegetables. Dr Weldon’s research group
is researching this species to obtain a better understanding of its dispersal and the susceptibility of commercial food and vegetable production to this pest.
Other than their importance in agriculture, flies are also useful in crime investigations.
Postgraduate research under Dr Weldon’s supervision
has focused on the use of blowflies as evidence in forensic investigations, as the presence and developmental stage of blowfly species on a corpse can provide information on the approximate time of death. For her Master’s research, Zanthé Kotzé found that estimates of post-mortem interval must take larval aggregation size into consideration because larger groups of larvae accumulate metabolic heat and develop faster as a consequence. Nina Parry established in her Honours research that there were differences in the distribution and abundance of carrion-associated flies in different habitat types in the City of Tshwane, which may prove useful in determining whether a body has been moved post-mortem.
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André Coetzer

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