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- ItemDisentangling the relationships among abundance, invasiveness and invasibility in trait space(Springer Nature, 2023-06-09) Hui, Cang; Pysek, Petr; Richardson, David M.Identifying conditions and traits that allow an introduced species to grow and spread, from being initially rare to becoming abundant (defined as invasiveness), is the crux of invasion ecology. Invasiveness and abundance are related but not the same, and we need to differentiate these concepts. Predicting both species abundance and invasiveness and their relationship in an invaded community is highly contextual, being contingent on the community trait profile and its invasibility. We operationalised a three-pronged invasion framework that considers traits, environmental context, and propagule pressure. Specifically, we measure the invasiveness of an alien species by combining three components (performance reflecting environmental suitability, product of species richness and the covariance between interaction strength and species abundance, and community-level interaction pressure); the expected population growth rate of alien species simply reflects the total effect of propagule pressure and the product of their population size and invasiveness. The invasibility of a community reflects the size of opportunity niches (the integral of positive invasiveness in the trait space) under the given abiotic conditions of the environment. Both species abundance and the surface of invasiveness over the trait space can be dynamic and variable. Whether an introduced species with functional traits similar to those of an abundant species in the community exhibits high or low invasiveness depends largely on the kernel functions of performance and interaction strength with respect to traits and environmental conditions. Knowledge of the covariance between interaction strength and species abundance and these kernel functions, thus, holds the key to accurate prediction of invasion dynamics.
- ItemAn Evaluation of High‑Risk HPV in Squamous Cell Carcinomas of the Lip in a South African Cohort(Springer Nature, 2024-05-06) Harbor, Sharon N.; Schneider, Johann W.; Solomons, Nadine; Sanderson, Micheline; Afrogheh, Amir H.Background To determine the prevalence of HR-HPV in a series of lip SCC from South African patients, using currently accepted HPV-testing methodologies and to define the clinical and histomorphologic features of HPV-associated lip SCC. Methods Fifty SCC of lip and 50 control cases were tested for HR-HPV using p16 and HR-HPV DNA PCR. p16-equivocal/positive and HPV DNA PCR-positive SCC were further evaluated for the expression of HPV-16 and HPV-18 mRNA transcripts using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) to confirm transcriptionally active HPV. Results p16 was positive in 22% (n = 11) and equivocal in 4% (n = 2) of the SCC. One p16-positive case showed positivity for both HPV-16 DNA and HPV-16 E6/E7 mRNA transcripts (HPV prevalence rate of 2%). The HPV-positive case was non-keratinizing and occurred in an 80-year-old female. The two p16-equivocal cases were HR-HPV DNA positive and mRNA PCR negative. p16 was found to have a positive predictive value of 9%. Conclusion Findings from our cohort of lip SCC suggest that HR-HPV may have an insignificant role in the pathogenesis of SCC at this site. Due to its low ppv, p16 is insufficient to establish HR-HPV infection in SCC of the lip. The combination of p16 and DNA PCR appears to correlate with the presence of transcriptionally active virus. HPV E6/E7 mRNA detection is the gold standard for identifying HR-HPV. mRNA testing is not widely available in sub-Saharan Africa due to technical and financial constraints; however, the test appears to be of great value in p16-equivocal lip SCC.
- ItemGenetic diversity of Listeria monocytogenes from the fish products, the fish food processing environment and clinical origin in the Western Cape, South Africa using whole genome sequencing(2023-12) Lambrechts, Karlene; Rip, Diane; Gouws, Pieter
- ItemThe impact of weevil predation on seed viability and agronomic performance of cowpeas, Vigna unguiculata L. (Walp)(2023-03) Dlamini, Welile; Wilson, Ida; Pieterse, Petrus; Swanepoel, Pieter
- ItemAn Exploration of Lower Limb Prosthetics Service Delivery in Namibia in Comparison to Global Standards(2023-03) Likando, Christopher; Mji, Gubela; Visagie, Surona