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Alien phytogeographic regions of southern Africa: numerical classification, possible drivers, and regional threats.

ABSTRACT: The distributions of naturalised alien plant species that have invaded natural or semi-natural habitat are often geographically restricted by the environmental conditions in their new range, implying that alien species with similar environmental requirements and tolerances may form assemblages and characterise particular areas. The aim of this study was to use objective numerical techniques to reveal any possible alien phytogeographic regions (i.e. geographic areas with characteristic alien plant assemblages) in southern Africa. Quarter degree resolution presence records of naturalised alien plant species of South Africa, Lesotho, Swaziland, Namibia and Botswana were analysed through a divisive hierarchical classification technique, and the output was plotted on maps for further interpretation. The analyses revealed two main alien phytogeographic regions that could be subdivided into eight lower level phytogeographic regions. Along with knowledge of the environmental requirements of the characteristic species and supported by further statistical analyses, we hypothesised on the main drivers of alien phytogeographic regions, and suggest that environmental features such as climate and associated biomes were most important, followed by human activities that modify climatic and vegetation features, such as irrigation and agriculture. Most of the characteristic species are not currently well-known as invasive plant species, but many may have potential to become troublesome in the future. Considering the possibility of biotic homogenization, these findings have implications for predicting the characteristics of the plant assemblages of the future. However, the relatively low quality of the dataset necessitates further more in-depth studies with improved data before the findings could be directly beneficial for management.

SUBMITTER: Hugo S

PROVIDER: S-EPMC3344867 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Alien phytogeographic regions of southern Africa: numerical classification, possible drivers, and regional threats.

Hugo Sanet S Van Rensburg Berndt J BJ Van Wyk Abraham E AE Steenkamp Yolande Y

PloS one 20120504 5

The distributions of naturalised alien plant species that have invaded natural or semi-natural habitat are often geographically restricted by the environmental conditions in their new range, implying that alien species with similar environmental requirements and tolerances may form assemblages and characterise particular areas. The aim of this study was to use objective numerical techniques to reveal any possible alien phytogeographic regions (i.e. geographic areas with characteristic alien plan ...[more]

PMID: 22574145

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Project description:Growing evidence suggests that chemicals in disparate structural classes activate specific subsets of PPARγ’s transcriptional programs to generate adipocytes with distinct phenotypes. Our objectives were to 1) establish a novel classification method to predict PPARγ-interacting and modifying chemicals and 2) create taxonomy labels to group chemicals based on their effects on PPARγ’s transcriptome and downstream metabolic functions. We tested the hypothesis that an environmental ligand highly ranked by the taxonomy, but that segregated from the therapeutic ligands, would induce white but not brite adipogensis. 3T3-L1 cells were differentiated in the presence of 76 chemicals (negative controls, synthetic nuclear receptor ligands known to influence adipocyte biology, suspected environmental PPARγ ligands). Differentiation was assessed by measuring lipid accumulation. mRNA expression was determined by highly multiplexed RNA-Seq and validated by RT-qPCR. A novel classification model was developed using an amended random forest procedure. A subset of environmental contaminants identified as strong PPARγ agonists were characterized further for lipid handling, mitochondrial biogenesis and cellular respiration in 3T3-L1 cells and primary human preadipocytes. The 76 chemicals generated a spectrum of adipogenic differentiation. We used lipid accumulation and RNA sequencing data to develop a classification system that 1) identified PPARγ agonists and 2) sorted agonists into likely white or brite adipocyte inducers. Expression of Cidec, was the most efficacious indicator for strong PPARγ activation. Two known environmental PPARγ ligands, tetrabromobisphenol A, and triphenyl phosphate, which sorted distinctly from therapeutic ligands, induced white but not brite adipocyte genes and induced fatty acid uptake but not mitochondrial biogenesis in 3T3-L1 cells. The highly ranked agonists, tonalid and quinoxyfen, also induced white adipogenesis in 3T3-L1 cells and primary human preadipocytes. A novel classification procedure accurately identified environmental chemicals as PPARγ-modifying chemicals distinct from known PPARγ-modifying therapeutics.

Dataset Information

Alien phytogeographic regions of southern Africa: numerical classification, possible drivers, and regional threats.

Publications

Alien phytogeographic regions of southern Africa: numerical classification, possible drivers, and regional threats.

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