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  • Publication
    Métadonnées seulement
    Can biochemical phenotype, obtained from herbarium samples, help taxonomic decisions? – A case study using Gentianaceae
    (2019-11-12)
    With the emergence of metabolomics, small quantities of plant material can be used to generate chemical fingerprints with high throughput for comparative analyses without the need for tedious and in-depth classical phytochemical investigation of large amounts of plant material. Here, we tested the hypothesis that herbarium samples themselves could be used as suitable material for untargeted metabolomic analysis and taxon discrimination based on biochemical phenotypes. We employed mass-spectrometrybased metabolite profiling to classify given species of chemotaxonomical relevance from the Gentianaceae family based on their biochemical phenotypic differences. Our dataset consisted of 605 accessions each with 910 mass spectral features, representing 59 species from 23 genera that extend over 6 tribes of the family. We found that minute amounts of herbarium specimens (less than 50 mg) were sufficient to obtain comprehensive fingerprints for all investigated individuals. Morphologically or genetically distinct species were differentiated using metabolite profiles, confirming taxon distinctions and validating the utility of this method for identification and differentiation. Overall, our results suggest that metabolite profiling of herbarium specimens may be suitable for taxonomic studies and also opens new ground for detailed investigations of their specialised metabolite contents.
  • Publication
    Métadonnées seulement
    Sebaea solaris (Gentianaceae), a new species from theWestern cape of South Africa
    Sebaea solaris (Gentianaceae) is here described as a new species from the Overberg region, Western Cape, South Africa. This new species is at first glance very distinct from all others in the genus mainly due to its relative large yellow flowers of c. 2.5 cmdiameterwith oblanceolate to obdeltoid erose corolla lobes. The petal ornamentation with several orange lines indicating the flower centre (versus two lines per petal for a few other Sebaea species) and a conspicuous undulated calyx wing are also unique in the genus. Furthermore, the position of large secondary stigmas above the middle of the style (versus at the base of the style for its morphologically closest relative: S. exacoides) possibly indicates differences in pollination strategies.
  • Publication
    Métadonnées seulement
    Back to Gondwanaland: can ancient vicariance explain (some) Indian Ocean disjunct plant distributions?
    Oceans, or other wide expanses of inhospitable environment, interrupt present day distributions of many plant groups. Using molecular dating techniques, generally incorporating fossil evidence, we can estimate when such distributions originated. Numerous dating analyses have recently precipitated a paradigm shift in the general explanations for the phenomenon, away from older geological causes, such as continental drift, in favour of more recent, long-distance dispersal (LDD). For example, the ‘Gondwanan vicariance’ scenario has been dismissed in various studies of Indian Ocean disjunct distributions. We used the gentian tribe Exaceae to reassess this scenario using molecular dating with minimum (fossil), maximum (geological), secondary (from wider analyses) and hypothesis-driven age constraints. Our results indicate that ancient vicariance cannot be ruled out as an explanation for the early origins of Exaceae across Africa, Madagascar and the Indian subcontinent unless a strong assumption is made about the maximum age of Gentianales. However, both the Gondwanan scenario and the available evidence suggest that there were also several, more recent, intercontinental dispersals during the diversification of the group.
  • Publication
    Métadonnées seulement
    Exochaenium clavatum subsp. stella-palustre (Gentianaceae—Exaceae), a new subspecies from Zambia
    Exochaenium clavatum subsp. stella-palustre is here described as a new subspecies from Zambia. It is characterized by its relatively small size (20 cm tall), leaves massed at the base of the stem and oriented downwards, a single, bright yellow flower, and a calyx wing broadest at the middle. Furthermore, this new taxon was collected in a dambo, in contrast to the inundated lakeshores where E. clavatum subsp. clavatum typically occurs. A key distinguishing the two subspecies is provided.
  • Publication
    Métadonnées seulement
    Taxonomy and Classification
    (New York: Springer, 2013)
  • Publication
    Métadonnées seulement
    Novel microsatellite loci for Sebaea aurea (Gentianaceae) and cross-amplification in related species
    • Premise of the study: Microsatellite loci were developed in Sebaea aurea (Gentianaceae) to investigate the functional role of diplostigmaty (i.e., the presence of additional stigmas along the style). • Methods and Results: One hundred seventy-four and 180 microsatellite loci were isolated through 454 shotgun sequencing of genomic and microsatellite-enriched DNA libraries, respectively. Sixteen polymorphic microsatellite loci were characterized, and 12 of them were selected to genotype individuals from two populations. Microsatellite amplifi cation was conducted in two multiplex groups, each containing six microsatellite loci. Cross-species amplifi cation was tested in seven other species of Sebaea . The 12 novel microsatellite loci amplifi ed only in the two most closely related species to S. aurea (i.e., S. ambigua and S. minutifl ora ) and were also polymorphic in these two species. • Conclusions: These results demonstrate the usefulness of this set of newly developed microsatellite loci to investigate the mating system and population genetic structure in S. aurea and related species.
  • Publication
    Métadonnées seulement
    Diplostigmaty in plants: a novel mechanism that provide reproductive assurance
    Differentiation of female sexual organs in flowering plants is rare and contrasts with the wide range of male reproductive strategies. An unusual example involves diplostigmaty, the possession of spatially and temporally distinct stigmas in Sebaea (Gentianaceae). Here, the single pistil within a flower has an apical stigma, as occurs in most flowering plants, but also a secondary stigma that occurs midway down the style, which is physically discrete and receptive several days after the apical stigma. We examined the function of diplostigmaty in Sebaea aurea, an insect-pollinated species of the Western Cape of South Africa. Floral manipulations and measurements of fertility and mating patterns provided evidence that basal stigmas function to enable autonomous delayed self-pollination, without limiting opportunities for outcrossing and thus avoiding the costs of seed discounting. We suggest that delayed selfing serves as a mechanism of reproductive assurance in populations with low plant density. The possession of dimorphic stigma function provides a novel example of a flexible mixed-mating strategy in plants that is responsive to changing demographic conditions.