Browsing by Author "Yekwayo, Inam"

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    Diversity value of Afromontane forest patches within KwaZulu-Natal timber production areas
    (Stellenbosch : Stellenbosch University, 2016-03) Yekwayo, Inam; Pryke, James S.; Roets, Francois; Samways, Michael J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Natural forests are important habitats for many species. In the KwaZulu-Natal Midlands of South Africa these forests naturally exist as small isolated forest patches within a grassland matrix. Recently, much of the extensive grassland matrix has been converted to exotic pine plantations. It remains unclear how this has affected the ecologically important forest arthropods. The overall aim of this study is to determine the state of arthropod diversity in natural forest patches within a timber production landscape, and how best to conserve this diversity. The specific objectives of this study are to: 1) determine the impact of natural forest interpatch distance and forest patch size on epigaeic arthropod diversity; 2) compare arthropod species richness, abundance and composition among natural forests, pine plantations and grasslands; 3) determine how each arthropod functional guild/taxon (detritivores, predators, herbivores, ants and mites) responds to pine plantations, natural forests and grassland, and assess whether exotic pine plantations are able to function as habitat extensions of natural forests compared to the natural reference of grassland. Natural forest patches and surrounding habitats were sampled for epigaeic arthropods using pitfall traps, Berlese-Tullgren funnels, and active searches. Large and small patches had similar species richness, while assemblages differed significantly. Greater ant richness was recorded in patches with closer interpatch distances, while the opposite was observed for mites. Interaction between patch size and interpatch distance led to large-close patches supporting ant, beetle and spider composition that is different from small-close patches. Additionally, small-distant and small-close patches supported different beetle and ant composition. However, large-close and large-distant patches supported similar overall assemblages. Natural forests surrounded by grassland maintain arthropod diversity better than those surrounded by pines. There were greater differences in assemblages between natural forest-grassland boundaries than between natural forest-pine boundaries, indicating edge effects between pines and natural forests. Furthermore, grassland supported higher ant richness, while the greatest richness of mites and detritivores was in natural forests. Natural forests and their surrounding habitats varied in assemblages among functional guilds, although natural forests and pines were similar in mite, herbivore and predator assemblages. Interestingly, some grassland associated species were often found in adjacent natural forests. Many natural forests associated species were also present in the surrounding pines, yet pine blocks negatively influenced natural forest associated mite species. All pine associated species were able to occupy adjacent natural forests. Small patches had higher arthropod diversity than expected, although large and close patches are of greatest conservation priority in this landscape. Nevertheless, effective maintenance of all forest patches must incorporate surrounding natural vegetation. Although pines had a negative impact on species richness, they were also important habitat for some forest species, even though this is associated with loss of grassland species. I show that pines are not true extensions of natural forests, as they do not support all natural forest arthropod species. This study highlights the important role that natural forests play in the conservation of native arthropod biodiversity in a production landscape, and by extension in maintaining ecosystem processes across this landscape.
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    Only multi-taxon studies show the full range of arthropod responses to fire
    (Public Library of Science, 2018-04-03) Yekwayo, Inam; Pryke, James S.; Gaigher, Rene; Samways, Michael J.
    Fire is a major driver in many ecosystems. Yet, little is known about how different ground-living arthropods survive fire. Using three sampling methods, and time-since-fire (last fire event: 3 months, 1 year, and 7 years), we investigate how ground-living arthropod diversity responds to fire, and how species richness, diversity, abundance, and composition of the four dominant taxa: ants, beetles, cockroaches and mites, respond. We did this in the naturally fire-prone Mediterranean-type scrubland vegetation (fynbos) of the Cape Floristic Region. Surprisingly, overall species richness and diversity was the same for all time-since-fire categories. However, when each dominant taxon was analysed separately, effect of fire on species richness and abundance varied among taxa. This emphasizes that many taxa must be investigated to really understand fire-driven events. We also highlight the importance of using different diversity measures, as fire did not influence species richness and abundance of particular taxa, while it affected others, overall greatly affecting assemblages of all taxa. Rockiness affected species richness, abundance and composition of a few taxa. We found that all time-since-fire categories supported distinctive assemblages. Some indicator species occurred across all time-since-fire categories, while others were restricted to a single time-since-fire category, showing that there is a wide range of responses to fire between taxa. Details of local landscape structure, abiotic and biotic, and frequency and intensity of fire add complexity to the fire-arthropod interaction. Overall, we show that the relationship between fire and arthropods is phylogenetically constrained, having been honed by many millennia of fire events, and highly complex. Present-day species manifest a variety of adaptations for surviving the great natural selective force of fire.