Towards an understanding of plant rarity in Kwazulu-Natal, South Africa

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2014.The persistence of rare plants is an important dimension in the conservation of biodiversity. Consequently an improved understanding of the nature and determinants of plant rarity and its relation with vulnerability to extinction could provide a basis for “proactive conservation” instead of the present day tendency for conservation actions to be “reactive”. In this dissertation I explore the relation between plant rarity and anthropogenic pressures (land transformation and use), biophysical factors, and plant traits in KwaZulu-Natal Province. Rarity was defined as the product of plant species abundance (population size) and its distribution (extent of occurrence). A number of a priori hypotheses regarding plant rarity were developed from the literature and these were then tested on a sample of plant species from KwaZulu-Natal. Species were selected in a stratified random manner to include species from different levels of threat and rarity or commonness. As the interest of this study was KwaZulu-Natal, only KwaZulu-Natal records were used for the analysis. Although the study suffered from a paucity of data particularly on the biological traits and behaviour of each species I was able to explore rarity in terms of seed dispersal distance, stress tolerance, habitat specificity and ecological niche width. I also explored potential island effects based on a species affinity to isolated erosional land surfaces and the anthropogenic effects of utilization and land transformation. To get an initial insight into relations, rarity was compared with each explanatory variable independently prior to using a multiple regression analysis approach aimed at understanding the potential interactive effects of suitable variables on rarity. Three different analytical techniques were used to provide a more robust understanding of the variable associations. These included Regression tree analysis (CART Salford Systems Inc., USA) and two generalized linear regression approaches; Generalized Linear Modelling (GLM) and Generalized Additive Modelling (GAM). All three multiple regression methods indicated that niche width had the strongest influence on rarity. Although Land Surface was shown to be the second strongest variable this, according to the GLM and GAM analyses, was due to a positive correlation between species with no affinity to land surface and species commonness. Visual representation of the regression tree analysis showed inconsistent partitioning of this variable throughout the tree indicating that land surfaces are not good predictors of rarity. Although the relation between Rarity Index and Habitat Transformation is not linear it was shown to be significant (p <0.1(p=0.0549)) after “smoothing” in GAM analysis. A smoothing curve on the bivariate analysis and the regression tree analysis indicated that species start to become rare after approximately 36% of their habitat is transformed. While GLM and GAM showed little or no relation between life history, dispersal distance, habitat specificity and rarity, the regression tree selected habitat specificity as the third most important splitter in the tree and dispersal distance was selected as a primary splitter for species with a niche width of greater than four. These differences observed in the three multiple regression analyses highlight the value of using more than one method to explore relations in ecological data. Considering all three analyses Niche Width is the strongest determinant of Rarity in KwaZulu-Natal, followed by Habitat Transformation and then Habitat Specificity. This improved understanding of the determinants of rarity will enhance our ability to prioritise plant species for conservation action. Key Words: ecological niche width, habitat specificity, habitat transformation, rarity, seed dispersal distance, stress tolerance, human use

Conduire le changement en bibliothèque

Comment conduire le changement de manière efficace dans le contexte très particulier introduit par les révolutions du numérique et des réseaux dans les bibliothèques ? Comment assurer le bon fonctionnement d’un équipement lorsque le rythme des changements à conduire s’accélère ? Ce volume apporte des éléments de réponses pratiques, tirées de réalisations concrètes et propose une réflexion plus générale sur les modalités du management en bibliothèque, centrée sur la notion émergente, dans les institutions publiques, d’organisation apprenante

The Worksite Health Promotion Capacity Instrument (WHPCI): development, validation and approaches for determining companies' levels of health promotion capacity

<p>Abstract</p> <p>Background</p> <p>The Worksite Health Promotion Capacity Instrument (WHPCI) was developed to assess two key factors for effective worksite health promotion: collective willingness and the systematic implementation of health promotion activities in companies. This study evaluates the diagnostic qualities of the WHPCI based on its subscales Health Promotion Willingness and Health Promotion Management, which can be used to place companies into four different categories based on their level of health promotion capacity.</p> <p>Methods</p> <p>Psychometric evaluation was conducted using exploratory factor and reliability analyses with data taken from a random sample of managers from n = 522 German information and communication technology (ICT) companies. Receiver operating characteristic (ROC) analyses were conducted to determine further diagnostic qualities of the instrument and to establish the cut-off scores used to determine each company's level of health promotion capacity.</p> <p>Results</p> <p>The instrument's subscales, Health Promotion Willingness and Health Promotion Management, are based on one-dimensional constructs, each with very good reliability (Cronbach's alpha = 0.83/0.91). ROC analyses demonstrated satisfactory diagnostic accuracy with an area under the curve (AUC) of 0.76 (SE = 0.021; 95% CI 0.72-0.80) for the Health Promotion Willingness scale and 0.81 (SE = 0.021; 95% CI 0.77-0.86) for the Health Promotion Management scale. A cut-off score with good sensitivity (71%/76%) and specificity (69%/75%) was determined for each scale. Both scales were found to have good predictive power and exhibited good efficiency.</p> <p>Conclusions</p> <p>Our findings indicate preliminary evidence for the validity and reliability of both subscales of the WHPCI. The goodness of each cut-off score suggests that the scales are appropriate for determining companies' levels of health promotion capacity. Support in implementing (systematic) worksite health promotion can then be tailored to each company's needs based on their current capacity level.</p

Active sexual reproduction but no sign of genetic diversity in range-edge populations of Vanilla roscheri Rchb. f. (Orchidaceae) in South Africa

International audienceIn South Africa, the wild leafless Vanilla roscheri Rchb. f. (Orchidaceae) is distributed only on the banks of the Lake Sibaya in KwaZulu-Natal Coastal Forest in the iSimangaliso Wetland Park. It is the southernmost vanilloid orchid on the African continent and a species of high conservation priority with little understanding of its reproductive biology and levels of genetic diversity. Mating systems and pollination ecology of the species were assessed by in situ experiments, in addition to genotyping plants at 16 microsatellite markers. Allogamous but self-compatible, V. roscheri depends on pollinators to achieve sexual reproduction. Its natural fruit set (26.3 %) is the highest reported for a non-spontaneously self-pollinating Vanilla species. It was associated with numerous flower visitors including two female allodapine bees (Allodapula variegata and Allodape rufogastra, Xylocopinae), captured with pollinia stored on the hind legs, and one female anthophorine bee. On the other hand, we report an absence of genetic diversity and homozygosity of the South-African populations of V. roscheri for all the genetic markers. Given the preferential outbreeding, the high natural fruit set and the pollinator/visitor richness of V. roscheri in Sibaya, a high level of genetic diversity was expected, but this was not the case. We detected a counterintuitive situation between the results of reproductive biology and genetics, making sense once the population situation on the margins of the species distribution is included. The null diversity expressed through the homozygous monomorphic markers is a consequence of the range-edge localization of the populations, which may have been subjected to severe bottlenecks (due to long distance colonization or fragmentation) along with inbreeding, in the past. The analysis highlights the complementarity of the approaches for which the implications in terms of conservation of the species in South Africa are discussed

Analysis of COX2 mutants reveals cytochrome oxidase subassemblies in yeast

Cytochrome oxidase catalyses the reduction of oxygen to water. The mitochondrial enzyme contains up to 13 subunits, 11 in yeast, of which three, Cox1p, Cox2p and Cox3p, are mitochondrially encoded. The assembly pathway of this complex is still poorly understood. Its study in yeast has been so far impeded by the rapid turnover of unassembled subunits of the enzyme. In the present study, immunoblot analysis of blue native gels of yeast wild-type and Cox2p mutants revealed five cytochrome oxidase complexes or subcomplexes: a, b, c, d and f; a is likely to be the fully assembled enzyme; b lacks Cox6ap; d contains Cox7p and/or Cox7ap; f represents unassembled Cox1p; and c, observed only in the Cox2p mutants, contains Cox1p, Cox3p, Cox5p and Cox6p and lacks the other subunits. The identification of these novel cytochrome oxidase subcomplexes should encourage the reexamination of other yeast mutants