Taxonomy and genetic structure of Meru oak populations, Vitex keniensis Turrill and Vitex fischeri Gürke, in East Africa

J.O. Ahenda

    Research output: Thesisinternal PhD, WU

    Abstract

    <p><em>Vitex keniensis</em> Turrill (Verbenaceae), the Meru oak, is a popular but threatened indigenous forest tree species in East Africa valued for high quality timber, fast growth, edible fruits, medicine, bee forage (honey). The tree has a high agroforestry potential. However, efforts to promote its propagation and conservation is hampered by lack of information on its biological and ecological characteristics. The taxonomic distinction between its populations in Mt. Kenya and Nyambene hills and those of <em>V. fischeri</em> in Lake Victoria and Mt. Elgon regions has been unclear. The research project investigated the taxonomy and compared the mating systems and genetic structure of the four populations of <em>V. keniensis</em> and <em>V. fischeri</em> .</p><p>The <em>Vitex</em> populations showed similarity in their leaf, flower, seed and seedling morphology, phenological pattern, polyploidy (2n=96) and autotetraploidy, homogamy, partial self-incompatibility, bee-pollination, inter-population reproductive compatibility and low inter-population variation 3.5%. These observations differed from the expected pattern of their geographical distance, ecological gradient and the current taxonomic grouping. The low population divergence could be attributed to common ancestry and possibly lack of divergence. <em>V. keniensis</em> and <em>V. fischeri</em> should be considered conspecific. The name <em>V. fischeri</em> has priority, the well-known name, <em>V. keniensis</em> (Meru oak) therefore falls into synonymy, thus <em>Vitex fischeri</em> (= <em>V. keniensis</em> ).</p><p>The bulk of genetic variation is within the populations (96.5%), therefore sampling from any of the four populations can capture a sufficiently large gene pool of the species for improvement breeding and conservation. It is a bee-pollinated, autotetraploid, therefore a minimum of a hundred dispersed mature trees at least 300 m apart can be preserved in-situ, and their propagules used for ex-situ conservation, breeding and propagation stock (living gene-bank).</p>
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • van der Maesen, L.J.G., Promotor
    • Hoekstra, R.F., Promotor, External person
    • Oballa, P.O., Promotor, External person
    Award date15 Sep 1999
    Place of PublicationS.l.
    Publisher
    Print ISBNs9789058081049
    Publication statusPublished - 1999

    Keywords

    • vitex
    • forest trees
    • taxonomy
    • morphology
    • genetic factors
    • genetic variation
    • endangered species
    • protection
    • afforestation
    • phytogeography
    • east africa

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