Impact of Seriphium plumosum densification on Mesic Highveld Grassland biodiversity in South Africa.

Mesic Highveld Grassland is important for biodiversity conservation, but is threatened by bush densification from Seriphium plumosum. This indigenous densifier spreads rapidly and outcompetes other herbaceous species, changing the species composition and structure of grasslands. This study looks at three different densities of S. plumosum and how these affect grassland biodiversity within Telperion, Mpumalanga, South Africa. An intermediate density of S. plumosum (1500 individuals (ind) ha-1) resulted in the highest plant species diversity (H = 2.26), a low density (24 ind ha-1) was moderately diverse (H = 1.96) and a high density (9500 ind ha-1) was least diverse (H = 1.78). There were differences between the three densities in terms of plant species diversity, with the intermediate density being significantly more diverse (p < 0.01) than both the low and high densities. Findings indicate that there was a significant difference between the sites in terms of ecological successional status (p < 0.01). The presence of S. plumosum at low densities can be considered an integral part of the environment. It is important that in areas where S. plumosum occurs, it should be monitored. If this species is not in balance within its environment and it starts becoming dense, it will negatively affect the biodiversity, species composition and structure of the habitat.

Climate induced stress and mortality in vervet monkeys.

As the effects of global climate change become more apparent, animal species will become increasingly affected by extreme climate and its effect on the environment. There is a pressing need to understand animal physiological and behavioural responses to climatic stressors. We used the reactive scope model as a framework to investigate the influence of drought conditions on vervet monkey (Chlorocebus pygerythrus) behaviour, physiological stress and survival across 2.5 years in South Africa. Data were collected on climatic, environmental and behavioural variables and physiological stress via faecal glucocorticoid metabolites (fGCMs). There was a meaningful interaction between water availability and resource abundance: when food availability was high but standing water was unavailable, fGCM concentrations were higher compared to when food was abundant and water was available. Vervet monkeys adapted their behaviour during a drought period by spending a greater proportion of time resting at the expense of feeding, moving and social behaviour. As food availability decreased, vervet mortality increased. Peak mortality occurred when food availability was at its lowest and there was no standing water. A survival analysis revealed that higher fGCM concentrations were associated with an increased probability of mortality. Our results suggest that with continued climate change, the increasing prevalence of drought will negatively affect vervet abundance and distribution in our population. Our study contributes to knowledge of the limits and scope of behavioural and physiological plasticity among vervet monkeys in the face of rapid environmental change.

Home range utilization by chacma baboon (Papio ursinus) troops on Suikerbosrand Nature Reserve, South Africa.

Rapid urbanization coupled with decreasing areas of natural habitat are causing baboon populations to become scattered and isolated, often resulting in increased levels of human-baboon conflict. To implement baboon-human conflict management strategies, it is essential to formulate realistic conservation policies that deal with all stakeholder concerns and ensure the conservation of viable baboon populations. A study was initiated in response to complaints of perceived excessive baboon numbers and associated lack of food resources on Suikerbosrand Nature Reserve in South Africa. Data obtained from GPS tracking collars fitted to one baboon from each of 10 identified troops were analyzed to determine home range size and utilization. The spatial representation of home ranges generated from this study will allow reserve management to identify areas of potential high and low human-baboon conflict and will contribute to the development of a formal baboon management plan to reduce human-baboon conflict on and around the reserve. Home ranges were unevenly distributed and had a mean size of 26.72 km2 ± 13.91 SD in the cold/dry season and 26.54 km2 ± 12.76 SD in the warm/wet season. Troop home ranges overlapped to some degree and five troops utilized areas outside the reserve. Although no significant relationship between troop size and home range was found, there was a positive relationship between troop size and daily distance travelled. All troops had significantly longer mean daily distances during the warm/wet season than during the cold/dry season (P ≤ 0.02).

Response to Comment on "Worldwide evidence of a unimodal relationship between productivity and plant species richness".

Tredennick et al. criticize one of our statistical analyses and emphasize the low explanatory power of models relating productivity to diversity. These criticisms do not detract from our key findings, including evidence consistent with the unimodal constraint relationship predicted by the humped-back model and evidence of scale sensitivities in the form and strength of the relationship.

Prevalence of hyperinsulinemia associated with body mass index, genetic predisposition, and lifestyle in college freshmen students.

OBJECTIVE: College lifestyle places an individual at greater risk for the development of insulin resistance (IR) and disease. The aim of this study was to establish a baseline measurement of insulin, and other variables influencing IR in college freshmen. PARTICIPANTS: Twenty-two men and women, 18 to 19 years of age, during first month of college. METHODS: Following 12-hour fast, subjects reported to the laboratory for determination of body mass index (BMI) and completion of questionnaire determining ethnicity, family history, and patterns of diet, exercise, and stress. Blood samples were obtained and analyzed for glucose and insulin. RESULTS: Mean insulin value for men (14.9 ± 1.86 µU/mL) was normal, and that for women (17.3 ± 1.74 µU/mL) was slightly elevated. When subjects were grouped by BMI, genetic predisposition, and summated lifestyle risk, fasting insulin values were significantly different. Eight of 22 subjects were hyperinsulinemic (insulin >19 µU/mL). CONCLUSION: Hyperinsulinemia is prevalent in this population and merits further investigation and intervention.