Browsing by Subject "Zamiaceae"

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    Insect pollination in the African cycad Encephalartos frederici-guilielmi Lehm
    (2009) Suinyuy, T N; Donaldson, J S; Johnson, S D
    Studies of the pollination ecology of the South African cycad, Encephalartos friderici-guilielmi Lehm, were carried out to determine the role played by insects and to identify the key pollinators. Surveys of insects on the male and female cones at the time of pollination indicated that three beetle species were present in sufficient numbers during pollination to be potential pollinators, i.e. an undescribed Erotylidae sp. (Cucujoidea), Metacucujus encephalarti (Cucujoidea), and Porthetes hispidus (Curculionidae). Pollen laden specimens of all three species were found on female cones with mean pollen loads ranging between 391 and 1019 pollen grains per beetle. In behavioural experiments, individuals of P. hispidus and M. encephalarti deposited fluorescent dye on the micropyles of receptive ovules. Enclosure of pollen laden specimens of P. hispidus, M. encephalarti, or Erotylidae sp. nov. on female cones resulted in seed set that was statistically similar to open controls and significantly higher than insect exclusion treatments. These data support the conclusion that E. friderici-guilielmi is insect pollinated and provide further evidence for the role of cucujoid (Erotylidae, Boganiidae) and curculionoid (Porthetes) beetles in the pollination of Encephalartos spp.
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    Scent chemistry and patterns of thermogenesis in male and female cones of the African cycad Encephalartos natalensis (Zamiaceae)
    (2010) Suinyuy, Terence; Donaldson, John; Johnson, S D
    Most, if not all, extant cycads are pollinated by insects which use the cones as larval brood sites. These interactions appear to be mediated by cone volatiles, and, in some species, by patterns of thermogenesis. We investigated the chemical composition of volatile emissions and patterns of thermogenesis in cones of the South African cycad Encephalartos natalensis, using a gas chromatograph–mass spectrometer (GC–MS) and miniature temperature data loggers (ibuttons), respectively. This was done during various developmental stages (before and during receptivity and pollen release) for both female and male cones. A total of 31 compounds were identified in headspace samples; 17 of which were common to both sexes, 12 found only in male cones, and two found only in female cones. The major volatiles in pollen and female cones are (3E)-1,3-octadiene (averaging 54.25% and 15.82% of total emissions), (3E,5Z)-1,3,5-octatriene (averaging 13.37% and 47.66%), and α-pinene (averaging 16.29% and 12.24%). Female cones were not thermogenic before and during receptivity whereas pollen cones were thermogenic during pollen shedding. Thermogenesis of male cones occurred between 1400 h and 1530 h on successive afternoons, reaching an average of c. 10.5 °C above ambient temperature. Volatile emissions and thermogenesis occurred in association with insect activity on the cones suggesting that they both play a role in regulating insect behaviour.