Browsing by Author "Donaldson, John Sidney"

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    Adaptation to the host-plant, and the evolution of host specialization, in 'cycad weevils' (Coleoptera: Brentidae)
    (1991) Donaldson, John Sidney; Moran, V C; Hoffmann John
    This thesis deals with host relationships in an enigmatic and seemingly primitive group of weevils belonging to the genus Antliarhinus (Coleoptera: Brentidae). These beetles occur only on species of the cycad genus Encephalartos and appear to retain an ancient association with cycads, a group of plants that were widespread in the Mesozoic era (ca. 200 MYA) before the rise of the angiosperms and which are now represented by 11 genera with relict distributions in the tropics and sub-tropics. The primary aim of this research was to determine the possible causes of narrow host specialization in Antliarhinus zamiae (Thunberg) and A. signatus Gyllenhal, two species which develop exclusively on the ovules of their cycad hosts.
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    The role of cone volatiles and thermogenesis in the pollination of Encephalartos cycads with particular reference to E.villosus
    (2011) Suinyuy, Terence Nkwanwir; Donaldson, John Sidney
    Pollination systems of cycads usually involve obligate mutualisms in which the cycad taxa depend on between one and three insect pollinators. Generally, the pollination periods of many cycad taxa are characterised by odour emissions in pollen shedding (male) and receptive (female) cones usually accompanied by heat production. The emission of cone odours and heat production coincide with periods of insect activity on the cones...