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Masters Degrees (Entomology)

Permanent URI for this collectionhttps://hdl.handle.net/10413/7535

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Browsing Masters Degrees (Entomology) by Subject "Ants."

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    Ant communities along an elevational transect, the Udzungwa Mountains in Tanzania.
    (2020) Kunene, Caroline.; Munyai, Thinandavha Caswell.; Foord, Stefan Hendrik.
    Understanding biodiversity patterns and the processes that structure them along environmental gradients has been a topic of major ecological interest. Although relatively well-known, alpha diversity is still poorly understood. It is therefore crucial to investigate alpha diversity patterns as they reveal how diversified species are within a site and identifies processes underlying the co-occurrence of species at a local scale. The patterns and processes related to beta diversity, however, have lagged even more behind. Beta diversity describes the variation in species composition between sites. It reveals whether species turnover or richness differences cause variation in community composition between sites. Together, alpha and beta diversity may provide baseline information for conservation planning, especially in African Tropics. African tropical rainforests, although very diverse, are some of the most threatened and understudied ecosystems of the world. Similarly, although the primary aim in ecology has been to document biodiversity patterns and the processes that structure them, those of invertebrates have lagged behind. As a result, very little is known about African tropical invertebrate patterns and the mechanisms that drive them. The current study, therefore aims (1) describe ant diversity patterns and community assemblages along the Udzungwa mountains, (2) to describe the extent of compositional differences between sites (beta diversity) and (3) to reveal the assembly mechanisms that drive these differences along an altitudinal gradient, Udzungwa Mountains, Tanzania. A standardized pitfall survey was conducted across five elevational transects, each at a distance of 0.1, 1, 20 and 174 km from the first one. Three target elevations which correspond to the three forest types of this mountain (lowland (300-800 m.a.s.l), sub-montane (800-1400), montane (1400-1500)) were selected. A total of 31 776 ant specimens were collected. They belong to five subfamilies, 34 genera and 101 species. Species richness declined with increasing elevation. Three species assemblages corresponding to the three forest types were observed across the mountains. The lowland assemblage was very distinct, while the sub-montane and montane assemblages were closely related. Results show that distance (km) and elevational distance (m.a.s.l) influence variation in community composition (beta diversity). Beta diversity increases with geographic and elevational distance, although more noticeable with elevation. The standardised effect sizes (SES) models suggest that species turnover increases with distance and elevation, while richness differences decrease with distance and elevation. Species turnover plays a significant role in structuring ant communities with increasing elevation while neither species turnover nor richness differences play a significant role in structuring ant communities with increasing geographical distance. The overall findings of this study, therefore, suggest that ants of the Udzungwa mountains are niche conservative, beta diversity is affected by distance and elevation and that species replacement structures ant communities with increasing elevation, while biotic interactions structure ant communities with increasing distance. Therefore, temperature is very important in structuring ant communities along the Udzungwa mountains and complementarity between sites is maximized by choosing sites that are at different elevations.
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    Ant diversity and composition in a reforested landscape of Buffelsdraai Landfill Conservancy, KwaZulu-Natal.
    (2019) Xolo, Sbongiseni.; Munyai, Thinandavha Caswell.; Slotow, Robert Hugh.; Foord, Stefan Hendrik.
    Restoration of degraded and reclaimed landscapes provide a useful framework to evaluate the recovery of biodiversity loss. A reforestation project was initiated in 2008 by eThekwini Municipality in Buffelsdraai Landfill Conservancy, aiming to offset carbon emissions over a 20-year period and increase climate change adaptation through biodiversity and ecosystem services restoration. The project offered an opportunity to evaluate to what extent reforestation for carbon sequestration can have co-benefits for biodiversity. The current study monitors the recovery of habitat restoration practices (planting of indigenous forest trees) in Buffelsdraai Landfill Conservancy, eThekwini Municipality, KwaZulu-Natal Province, in South Africa. The main aim of the study was to evaluate how biodiversity recovers following forest restoration. The study used ants (Formicidae: Hymenoptera) as a model organism as they comprise a significant component of invertebrate diversity and a keystone taxon in the terrestrial ecosystems. The study objectives were to provide ant checklist in a reforested landscape and to describe ant diversity patterns along a gradient of restoration and to identify the environmental variables which drive the diversity patterns along a reforestation gradient. Using a standardized pitfall survey, ants were sampled across eight sites, each replicated four times, which included sugarcane (unrestored), grassland and scarp forest (natural reference sites), short-term (0-2 year), medium-term (3-5 years) and long-term (6-8 years) restored sites. Ant sampling was conducted in April-May 2017 (early dry season) and December 2017 (wet season). Environmental (habitat structure) and soil surveys were conducted at each plot. A total of 27 439 ant specimens comprising of 96 species in 31 genera, and six subfamilies were collected. Sample coverage estimator was larger than 0.97, indicating that inventory completion approximated most of the ant assemblages found in the study area. Myrmicinae, Ponerinae and Formicinae were the most abundant and species-rich subfamilies, with Tetramorium, Pheidole and Monomorium as the most species-rich genera. The most numerically dominant species were Pheidole megacephala species group and Anoplolepis custodiens. Ant species richness and activities were significantly highest in the restored and grassland sites and low in forest site, and lowest in unrestored sugarcane. Species richness responded with a hump-shaped response as patterns of species richness significantly decreased with increasing bare-ground cover. High species diversity and composition was associated with open habitats with grass layer. Forest had the most distinct assemblages. Leaf litter, vegetation structure, canopy cover and bare-ground cover, were the four predictor variables which had major influences on ant assemblage structure. Four forest indicator taxa were identified (Pheidole UKZN_11 (megacephala gp.), Tetramorium UKZN_04 (squaminode gp.); Tetramorium UKZN_28 (setigerum gp.) and Leptogenys attenuate), and one indicator for grassland (Lepisiota capensis). No indicators were found for sugarcane sites. Solenopsis UKZN_01 and Pheidole UKZN_09 were potential indicator for restored sites. The restoration sites were transitioning from sugarcane plantation, and were drawing most of their colonisation from grasslands at this stage. This study shows that open woodlands are ideal habitats for maximising species diversity, as they provide a complex habitat for many species, and the availability of local natural grassland as a source of invertebrates assists restoring functioning, even if we expect the community to transition to forest species as regrowth progresses.
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    Ant diversity, assemblage composition and other arthropod activities in relation to the invader Parthenium hysterophorus L. (Asteraceae) and its biological control agent.
    (2022) Hlabisa, Fanelesibonge Samkele.; Munyai, Thinandavha Caswell.; Strathie, Lorraine W.
    Invasive alien plants have the potential to alter ecosystem function. While a growing number of studies have focused on the effects of invading plants on native biodiversity and the underlying community dynamics, there is still a lack of studies that detail the impact of invasive plants, such as Parthenium hysterophorus L. (Asteraceae), at higher trophic levels. This study investigated whether P. hysterophorus and its biological control agent, the stem-boring weevil Listronotus setosipennis (Hustache) Coleoptera: Curculionidae, affected ant diversity, assemblages and arthropod activities in the KwaZulu-Natal and Mpumalanga provinces of South Africa. The objectives of this study were to assess the impacts of P. hysterophorus invasion and presence of L. setosipennis on the diversity and assemblage composition of ants, a dominant terrestrial group. Additionally, whether vegetative variables in habitats invaded by P. hysterophorus affected ant assemblages, was examined. Lastly, the study investigated the impacts of the presence and absence of L. setosipennis on other arthropod activities. To study ant diversity and assemblage composition, ants were collected using pitfall traps, over five sampling periods from December 2019 to March 2020, in nine locations around KwaZulu- Natal and Mpumalanga provinces. At each site, three treatments were sampled; viz. P. hysterophorus invaded habitat, P. hysterophorus invaded habitat with L. setosipennis present, and habitat without P. hysterophorus. Species richness and abundance were compared between treatments using ANOVA and the Post-hoc Turkey test. Assemblage composition was analyzed using non-metric multidimensional scaling (NMDS). A Canonical Correspondence Analysis (CCA) was also used to correlate the best environmental variable with ant diversity and assemblage composition. Some 16 463 ant specimens that were collected were identified from four subfamilies, 27 genera, and 55 species. Results indicated that the presence of P. hysterophorus and its biological control agent L. setosipennis did not significantly alter ant diversity, as indicated by species richness and abundance, and assemblage composition, although some differences occurred across locations. The results also showed that vegetative variables (P. hysterophorus height, flowering and cover) did not significantly influence ant assemblages. A separate experiment at six locations in KwaZulu-Natal and Mpumalanga provinces, arthropod activities on P. hysterophorus plants were studied during timed observations at 07h00, 10h00 and 12h00 during monthly sampling from December 2020 to March 2021. Although some arthropod groups were less common visitors to P. hysterophorus than others, this study showed that the presence of L. setosipennis had no significant effect on overall arthropod activities. However, results demonstrated greater activity for some arthropod groups, specifically Hymenopterans, in both treatments, accounting for 60% of all arthropods recorded. Other studies have reported either a positive or negative impact on arthropods by invasive alien plants. These plants may provide a better food resource for native insects and other arthropods, causing them to be attracted to them. However, invasive alien plants have also been linked to a decline in invertebrate species diversity or changes in the composition of populations. This study contributed to growing knowledge on the impacts of invasive alien plants and on terrestrial arthropods, the most prominent group of invertebrates, that are also known to be significant indicators of biological change.