Browsing by Author "Van der Niet, Timotheus"

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    Can and do Ericas self pollinate?
    (2011) Arendse, Brittany; Van der Niet, Timotheus; Midgley, Jeremy J
    Within the Cape Floristic Region many lineages are characterised by large floral diversity. The genus Erica is one of these lineages, making up -7% of the CFR. Surprisingly, even though pollinators have been suggested to be a driving force of floral morphology, the role of pollinators in the floral diversification and speciation of this genus is not yet well understood. Therefore the aim of this paper was to establish if Erica species can and do self-pollinate. Two Erica species, E. plukenetii and E. urnaviridis, were obtained from Kirstenbosch nursery, where hand-pollinations were performed on 15-20 flowers of each of three treatments (self-pollination, crosspollination and autogamous self-pollination. Additionally pollen tube analyses were performed on seven Erica species, which were collected from the Constantia Mountain. In E. plukenetii, self-incompatibility seems to be the predominant breeding system. It appears that, like E. urna-viridis, most of the other species analysed, via pollen tube analyses, have the potential to self-pollinate. However, more experiments are required to establish if these species are truly self-compatible. Autogamy, on the other hand, does not appear to set seed in the species studied. Therefore it would be fair to say that some ericas can self-pollinate but none actually do self-pollinate. These results indicate that ericas have a strong dependence on pollinators for seed set and in the past speciation may have occurred due to adaptation to different pollinators, when opllinators were scarce.
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    Intraspecific variation in Erica coccinea
    (2013) Malan, Michelle; Midgley, Jeremy J; Van der Niet, Timotheus
    The genus Erica is the most specious in the Cape Floristic Region, with a large range of habitats, pollination syndromes and fire survival strategies. Erica coccinea, like many other Cape Erica species, has high intraspecific variability between populations. In addition to variability in floral characteristics such as colour, this species includes two distinct regeneration forms: a resprouter form which survives fire by resprouting from dormant buds in a swollen lignotuber, and a seeder form which does not survive fire, but whose populations regenerate from fire-triggered seed germination. Previous studies have shown that these two regeneration forms are genetically determined and this dissertation investigates further the differences in floral morphology, phenology, fecundity and genetic relatedness across 29 populations. Results show patterns of seeder individuals investing more effort into nectar and seed production than resprouters and differences in flower colour and flowering phenology between the two fire life history strategies. A PST-FST analysis, comparing genetic variability to variability in floral traits shows a strong selective force working on anther length in the seeder form. A complete separation of flowering phenology between seeder and resprouter individuals in 'mixed' populations where the two forms co-occur leads to speculation that this might be a case of incipient speciation.