Browsing by Author "Dignon, Niki"

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    Quantifying bird damage to wine grapes in the Western Cape of South Africa : a questionnaire-based approach
    (2013) Dignon, Niki; Amar, Arjun
    Bird-wine grape damage is a globally acknowledged problem that has been the subject of considerable research in many wine growing regions. However, despite the Western Cape of South Africa being a major wine grape growing region, very little research has quantified bird damage in this region and very little is known about the extent of the problem. This research aimed to quantify bird damage to wine grapes in four grape growing regions of the Western Cape, through questionnaires. It also aimed to determine the factors that might explain the patterns of damage observed. 102 questionnaires were sent to the wine farms, and 52 were returned. Of the respondents, 71% reported bird grape damage. The amount of damage per wine farm ranged between 0% and 15% of the total rows of vines across a farm. When exploring the factors associated with whether a wine farm experienced bird damage, it was found that the border habitat of a farm was a significant factor. The composition of the border habitat greatly influenced the probability of bird damage. The PCA showed that tall trees, Fynbos and residential areas specifically increased the probability of bird damage. Within farms that experienced damage, it was found that in different vineyard blocks the areas closer to the edge of a vineyard and to trees were significantly more susceptible to bird damage. The most common reported damage-causing bird species were Red-Winged Starlings (Onycognathus morio) and White-Eyes (Zosterops lateralis). Damage was reported to occur mostly one month before harvest and at harvest time. This research provides a baseline for understanding the nature of bird damage in these regions and will aid future quantitative studies aimed at the management of the problem.
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    The Reproductive biology of Erica pudens
    (2013) Dignon, Niki; Midgley, Jeremy J
    Erica is the largest genus in the Cape Florisitic Region (CFR) boasting a diverse range of floral morphology and pollination systems. Even though it is such a diverse genus, there is minimal research examining the pollination biology of specific species. This research inspects the pollination biology of Erica pudens. To do this we carried out pollinator exclusions, hand pollination experiments, rodent trapping, camera observations and pollen/ovule counts. This research also establishes whether E. pudens is another example of convergent evolution in Erica by establishing its phylogenetic position. E. pudens possesses floral characteristics that are consistent with the rodent-pollination syndrome. These characteristics include tightly-packed, pendulous inflorescences with a prostrate habit, found close to the floor, with a dull flower colour and winter flowering times. This research also found that E. pudens offers a high volume of nectar per floral head (up to 20.9μl) with a comparably high sugar concentration (23.7%). Even though these characteristics suggested rodent-pollination, there was no other evidence that conclusively demonstrated this. Only three rodents were captured, and few pollen tetrads were found in the faeces of the two Rhabdomys pumilio individuals (average of 13 and 1 respectively). There was very little footage captured of rodent activity around E. pudens flowers and none to demonstrate the foraging activities of a potential pollinator. The exclusion of pollinators showed no significant difference in swollen ovule dimensions between bagged flowers and caged flowers. Breeding experiments showed no significant difference between self-pollinated flowers and cross-pollinated flowers. These results suggested no need for a pollinator and the ability of E. pudens to undergo self-pollination. This could be an example of pollinator failure (due to small rodent populations) and the consequent evolution of self-pollination. The phylogenetic studies showed that E. pudens was another example of convergent evolution within Erica.