Faculty of Natural and Agricultural Sciences
Department of Zoology and Entomology
Selected Highlights from Research Findings
A phytoplasma has been recorded in 2006 for the first time from grapevine in South Africa. Aster yellows (AY) phytoplasma (16Srl group) has been spreading in two regions in the Western Cape. It is currently classified as a quarantine organism in South africa. The disease has been recorded from a broad host range, including woody, vegetable and ornamental plants in other countries. Economic losses caused by infection of economically important cultivated plants can be severe. Identification of the vector(s) is essential if disease spread is to be managed. A first vector, the leafhopper Mgenia fuscovaria has been identified in controlled transmission experiments since the initiation of the project in 2009. Field trial data suggest that the time of AY infection in the field coincides with large numbers of M. fuscovaria being present in the field. The idenfification of a vector is of great benefit for the grapevine industry as it allows for the implementation of target control measures. Only a few vectors of phytoplasmas infecting grapevine are known to date and identifying vectors has proved difficult in other countries. For example, in Germany a vector was identified only after 17 years. The project managed to identify a vector of Aster yellows on grapevine within a year. This is the first report of a vector of AY in South Africa and of M. fuscovaria as a vector of AY.
Contact person: Dr K Krüger.
Continued stability (1994-2009), and perhaps increase, of the southern elephant seal population at Marion Island after a precipitous population decline since the 1970s. Renewed impetus in demographic and foraging ecology studies of this species. Increased research on Marion Island fur seal population ecology, in an attempt to better understand top-predator interspecific interactions. Initiation of dedicated killer whale foraging and demography study at Marion Island. Successful grant applications to this end. Photogrammetric method for estimating mass of large mammals (developed with elephant seals), applied successfully to a variety of large terrestrial large African mammals.
Contact person: Dr PJN de Bruyn.
Hidden beneath the sands of the Kalahari desert is the social Damaraland mole-rat which has developed a remarkable caste system. In the life of these animals, some smaller and not necessarily younger mole-rats develop into frequent workers, while larger and not necessarily older individuals become infrequent workers. With a relaxation of ecological constraints such as a period of good rainfall these infrequent workers disperse and become reproductively activated. In addition, the females from the infrequent worker caste on attaining reproductive status become more elongated and their skull dimensions different to that of philopatric female litter mates - such that a morphological caste is established. This finding adds to the growing body of literature that suggests that Damaraland mole-rats exhibit a morphological caste in the primary reproductive division of labour. Evolution 64: 3190-3197
Contact person: Prof NC Bennett.
Termites are considered to be major ecosystem engineers in tropical environments. However, they are often neglected and under studied, especially in grassy systems. The interaction between termites and fire ecology is one example of this. Given the importance of both fires and termites in savanna systems, it is critical for an improved ecological understanding of savanna biodiversity that the interaction between them is better understood. In this paper, we highlight the lack of published literature on fire ecology and invertebrates in austral systems, with particular focus on termites. We review the six studies conducted in savannas spanning the southern hemisphere which investigate this interaction, summarizing their findings and limitations. We suggest areas of future research related to fire and termites which will improve our ecological understanding of savannas and the dynamics that structure these systems.
Contact person: Prof BJ Van Rensburg.
The continuous expansion of large-scale agriculture threatens natural habitats and the pollination services that they offer. Creating patches of high plant diversity within farmland is commonly suggested as a measure to benefit pollinators. However, farmers are more likely to remove weeds. By combining pollinator exclusion experiments with analysis of honeybee behaviour and flower visitation webs, we found that the presence of weeds allowed pollinators to persist within sunflower fields. Weed diversity increased flower visitor diversity, compensating for the negative effects of isolation from natural habitat. Although honeybees were abundant on sunflowers, other flower visitors enhanced honeybee movement and so increased pollination. Conservation of natural patches combined with promoting flowering plants within crops can contribute towards sustainable agriculture.
Contact person: Prof SW Nicolson.
Continued stability (1994-2009), and perhaps increase, of the elephant seal population at Marion Island after a precipitous population decline since the 1970s. A major grant from NRF and the DST within SANAP was allocated to continue investigating the population dynamics and foraging ecology of seals at the Prince Edward Islands (2009-2013). Continued recovery and re-deployment of Satellite-linked CTD (Conductivity, Temperature, Depth) recorders on southern elephant seals at Marion Island within the International Polar Year (IPY) collaborative projects 'Marine Mammals as Oceanographic Platforms, Pole to Pole' (MEOP, IPY project no. 153) which enabled us to describe the at-sea foraging areas of southern elephant seals. Successful survey of the Prince Edward Island fur seal populations and the 27th anniversary of the continuous southern elephant seal mark-recapture programme at Marion Island (1983-2010).
Contact person: Prof MN Bester.
1. We wrote a review of biological atlas datasets, which include atlases such as the Southern African Bird Atlas project. The review focused on the use of these datasets in conservation and how the atlases and their use can be improved. The review was published in Diversity and Distributions 16, 363-375. 2. We found models appeared to be unaffected by geographical bias in occurrence records used to train models that were used to predict potential distributions in the invaded ranges of invasive plants. The findings were published in Journal of Biogeography 37, 1797-1810.
Contact person: Dr MP Robertson.
Our research focus on the development of sub-continental scale conservation management options for elephants continued and was boosted by the first ever quantification of behaviourally-mediated density dependence in savanna elephants. We showed that under natural conditions roaming distances of breeding herds increased with density (numbers per unit areas), while the survival of weaned calves decreased with increasing roaming distances. Provisioning of artificial water sources and fencing of conservation areas negated this dependence and this may explain some of the anomalous elephant population growth rates observed in these parks. Implementation of advice emanating from these findings provides a new and attractive approach to conservation management.
Contact person: Prof RJ van Aarde.
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