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Thesis (M. Sc. (Botany)) -- University of Limpopo, 2022 / Nature reserves are reservoirs for biodiversity. Their very purpose is to preserve indigenous fauna and flora and thus protect associated ecosystem services. The Schuinsdraai Nature Reserve of rural Sekhukhune District, Limpopo Province, is the focus of this study. Sekhukhune District is predominantly rural, with limited economic opportunities but rich mineral resources, the mining of which negatively impacts biodiversity. The Sekhukhune Centre of floristic endemism falls within this district and the nature reserve is thus an important factor in safeguarding a representative section of this floristic center. The veld type present in the reserve is central sandy bushveld. Although mining is prohibited within the reserve, invasive alien plants or (IAPs) pose as high a threat to biodiversity as does mining. The spread of IAPs in nature reserves is harder to control than mining which is prohibited outright whereas IAP spread is automatic and insidious. The management of IAPs is of concern to the government of South Africa and is an ongoing process. Rural areas and the nature reserves within them, such as the Schuinsdraai Nature Reserve, are often under studied or under managed with regards to IAPs. This study supplements the available but scarce data on IAPs for Schuinsdraai Nature Reserve. The Schuinsdraai Nature Reserve is dominated by the Central Sandy Bushveld vegetation type. Rainfall is on average 470 mm per year and mean annual temperature varies from 24 ˚C in the summer, to 14 ˚C in the winter. The topography includes mountains, hills, plains, and the Flag Boshielo Dam. The aims of the study were to establish the presence and extent of IAPs in the Schuinsdraai Nature Reserve and to determine whether the IAPs present negatively affect the biodiversity. Road-side inspections, road surveys and line transects were used to investigate presence and extent of IAPs. Modified Braun-Blanquet quadrates were used to compare the effect of the most prevalent IAPs on the plant biodiversity in the Schuinsdraai Nature Reserve. Quadrates were positioned in areas heavily infested by species of IAPs and these areas compared with untransformed areas within 10 m of the infested quadrates. Species richness, species evenness and v biodiversity indices were calculated for transformed (control) areas compared with infested areas. Roadside inspections and road surveys indicated the presence of IAPs. They revealed that most IAPs were present on the eastern side of the nature reserve closest to areas most visited by tourists. Roads and the movement of people therefore affect the spread of IAPs within the Schuinsdraai Nature Reserve. The four most prevalent species identified from roadside inspections and road surveys were: Opuntia stricta, Cylindropuntia fulgida, Cereus jamacaru and Boerhavia diffusa. Opuntia stricta had the greatest negative effect and was also the most prevalent IAP on the Schuinsdraai Nature Reserve. The number of IAPs per transect observed in the area where access was unlimited was significantly higher than where access was limited. Opuntia stricta was the IAPs exhibiting the most significant (.00057) impact on species richness and species diversity and, where funds are limited, these should be targeted for eradication rather than other IAPs. From the results obtained, management recommendations were tabled including the most important, which is to clearly demarcate areas where public movement should be restricted, and meticulously patrol areas which are open to the public and remove IAP’s immediately. In conclusion, IAPs are present and do cause deleterious effects on species richness, diversity and evenness within the Schuinsdraai Nature Reserve, however, the strict management of anthropogenic influences should be implemented to control their spread and increase.

This dissertation consists of two topics. Chapter 1 explores the relationship between firm transparency and managerial behaviors of the U.S. Property-Casualty (P&C) insurers. Using data between 1996 and 2015, we test whether credit rating agencies (CRAs) provide useful information to monitor insurers’ loss reserve management behaviors as watchdogs. In addition, we investigate how insurers recognize the rating difference given by different CRAs. We find that holding a rating does not necessarily affect insurers’ reserve management behaviors. However, loss reserve estimation tends to be more accurate as more ratings are given to an insurer. Such findings suggest that multiple CRAs stimulate insurers to accurately estimate their reserves through the enhanced monitoring function. We also find a marginal impact of rating difference on an insurer’s loss reserve estimation. Firms with rating difference tend to underestimate their loss reserves. Nevertheless, this does not considerably deteriorate the reserve forecast accuracy. Although the Sarbanes–Oxley Act (SOX) aims at regulating publicly traded firms, it seems to affect over the market. Our empirical results show that insurers’ reserve estimation accuracy is improved after the enactment of the SOX. Moreover, the enactment of SOX alleviates an under-reserving behavior of firms with rating difference. Chapter 2 investigates the derivative practice of the U.S. life insurers. Over the last two decades, derivatives have been used extensively as a risk management tool in the financial market. In the U.S. insurance market, life insurers have accounted for over 95% of total derivative transactions, a proportion much higher than that in other countries. However, there are only a few prior studies examining the practical use of derivatives in the U.S. life insurance market. In addition, several limitations exist in terms of data they used (single-year, outdated, and inaccurate). In this study, we compile accurate derivative transaction data by taking a close look at the underlying asset and the traded market. We then examine the determinants of derivative (swap in particular) participation and the extent of transactions using samples from 2001 to 2015 which includes major events such as the U.S. financial crisis and the Dodd-Frank Act. We find that the determinants of derivative/swap participation are different from those of transaction volumes. We also find that the impact of the financial crisis on derivative usage is very limited in the life insurance market. However, the enactment of the Dodd-Frank Act not only reduces the likelihood of swap participation but also stagnates the growth of the swap transaction volumes, while the total derivative transaction volumes are significantly increased. Such findings indicate that the costs of the new regulation outweigh its benefits, due to the inefficient and inadequate regulatory changes. / Business Administration/Risk Management and Insurance

Aging is characterized by an increase in inter-individual variability in cognitive capacity. Slight decrements in learning and memory emerge; however, age-related shifts in attentional function remain controversial. In pathological aging, however, attentional dysfunction is prominent and the circuitry critical to signal detection and thus attention as a whole, the corticopetal cholinergic system, exhibits substantial disruption and deterioration. One contributing factor to cholinergic dysfunction is the loss of neurotrophic support, specifically nerve growth factor’s high-affinity receptor tropomyosin-related kinase A (trkA). Previous cross-sectional studies demonstrated that reduced trkA receptor levels selectively impaired attentional capacity in aged rats. However, it remains unclear if reduced trkA receptors in the basal forebrain (BF) interact with aging to elicit these attentional deficits. Thus developmental suppression of trkA receptors on attentional capacity and BF cholinergic markers was examined, with the expectation that attentional deficits would emerge earlier in trkA-suppressed rats and cholinergic integrity would be altered. Despite persistent trkA suppression and reduced cholinergic cell size in 6-week-old rats, aged rats that were maintained on a cognitive task throughout life exhibited comparable attentional capacity and stable cholinergic markers compared to controls. Thus, activation of a compensatory mechanism may have stabilized the attentional network. Due to continuous performance on the attentional task, lifelong cognitive engagement may have served to bolster cholinergic integrity and stabilize attentional function. To examine the role of compensatory mechanisms in aging and their interactions with the attentional network, a consistently observed neural activation pattern in aging, termed the anterior-to-posterior shift in aging (PASA), was evaluated. PASA is characterized by enhanced frontal and reduced visual neural activity. Thus, the necessity of cholinergic afferents to the maintenance of PASA was investigated, as well as the role of PASA in stabilizing cognitive function in aging. If cholinergic afferents, specifically those innervating the prefrontal and posterior parietal cortices (PFC; PC), were crucial to PASA then partial cholinergic pruning of the PFC was expected to disrupt PASA and produce attentional deficits. Prefrontal infusion produced attentional deficits in aged rats regardless of infusion type, and elicited a corresponding age-related shift in neural activity, with decreases in visual and increases in parietal cortical activation in aged rats. Partial parietal cholinergic deafferentation impaired performance in both young and aged rats and altered prefrontal cortical recruitment, which was correlated with attentional performance in young rats. Increased recruitment of the attentional network was associated with worse performance in aged rats. Thus, prefrontal and parietal cholinergic afferents are not critical to PASA and increased activation may be representative of reduced neural efficiency rather than compensation. Moreover, aged rats rely heavily on the prefrontal cortex for attentional function, and aberrant prefrontal activity, via generalized damage or disruption of parietal cholinergic inputs, is associated with attentional impairments. Together these findings suggest that enhanced vulnerability of attentional capacity due to prefrontal disruption arises in aging; however, activation of compensatory mechanisms, such as lifelong cognitive activity, may bolster cholinergic integrity and stabilize cognitive function in aging. / Psychology