Browsing by Author "Potts, Alistair"

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    Heuweltjies : a window into the palaeoclimate and palaeovegetation of the Western Cape?
    (2006) Potts, Alistair; Midgley, Jeremy; Harris, Chris
    Late Pleistocene terrestrial climate information in the Western Cape. South Africa may be preserved in oxygen and carbon isotope ratios in paedogenic calcrete that bas Conned in zeuweltjies (large circular earth mounds). He11weltjles are common landscape features and their potential as palaeoclimatic archives is not known, simply because it has never been investigated. Samples were taken from three depth-profiles down a single hemvcltjie near Worcester. Carbon and oxygen isotope ratios were detennincd. In total, fifty-four samples were analysed. The o13C values vary from -7.4%. to -4.9%0 relative to PDB. whereas 15180 vary from 28.05'160 to 30.91%0 relative to SMOW.
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    Morphological and molecular analyses for the characterization of Aspalanthus linearis (Fabaceae: rooibos)
    (2006) Potts, Alistair; Verboom, George Anthony; Hoffmann, Timm
    I investigated the infraspecific diversity among individuals of Aspalathus linearis from five localities in the Cederberg Fynbos region using morphological traits and two DNA- based methods: inter-simple sequence repeats (ISSR) and a plastid marker. A principle component analysis (PCA) based on seven morphological variables grouped the samples into three different growth forms, specifically an erect-form, a prostrate-form and a shrub-form. The genetic variability of four plastid markers and one nuclear marker was determined for seven individuals selected from the populations. The trnL'UAAF-trnFGAA plastid marker was used to amplify the remaining samples and revealed four haplotypes, with a basal haplotype fixed in both the prostrate form and a single population of the erect form, a unique haplotype fixed in the shrub form, and a mix of two other haplotypes in the remaining erect forms. The congruence between haplotypes and regeneration strategy suggests a longstanding pattern of restricted gene flow. However, a small sample size associated with the plastid marker data limits or reduces the certainty of these findings.