Melanie Schneemilch

Publications (3)4.56 Total impact

• Article: Pollen tetrad segregation and pollen ovule ratios in six species of Acrotriche (Styphelioideae: Ericaceae)

  Melanie Schneemilch, Michael Kokkinn
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  ABSTRACT: Pollen morphology can be useful in the determination of phylogeny and mating systems of plants. Pollen ovule ratios can give an indication of the mating system of plant species, and there are a number of theories as to reductions in response to pollination strategies. Pollen tetrad segregation occurs when a number of pollen grains within a tetrad abort; this process has evolved a number of times in the family Ericaceae. Pollen ovule ratios along with the total number of tetrads, number of viable grains and proportions of each of the tetrad types were investigated in six species of Acrotriche (Styphelioideae: Ericaceae). Pollen ovule ratios were used in comparison with related species to give indications of mating systems and to examine theories regarding reductions in pollen production. The study species can be arranged into distinct groupings based on the proportions of tetrad types that correlate with floral morphology and may be indicative of phylogentic associations. KeywordsTetrad segregation–Heterodynamospory–Variable sterility–Pollen ovule ratios–Stypheliodeae–Secondary pollen presentation
  Plant Systematics and Evolution 05/2012; 296(3):149-156. · 1.34 Impact Factor
• Article: Flowering timing prediction in Australian native understorey species (Acrotriche R.Br Ericaceae) using meteorological data.

  Melanie Schneemilch, Michael Kokkinn, Craig R Williams
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  ABSTRACT: The aim of this study was to determine the climatic influences on floral development for five members of the Australian native plant genus Acrotriche R.Br (Ericaceae). An observed period of summer floral dormancy suggests temperature is involved in flowering regulation in these species. Models were developed to determine temperature requirements associated with the likelihood of flowering occurring on any one day. To this end, the timing of flowering and meteorological data were collated for several sites, and multivariate logistic regressions performed to identify variables with a significant influence on flowering timing. The resultant models described a large amount of variation in flowering presence/absence, with (r2) values ranging from 0.72 to 0.79. Temperature was identified as influential on both floral development and flowering timing in each of the study species. The positive influence of short photoperiods on flowering in three of the winter flowering species was not surprising. However, the reporting here ofa significant association between interdiurnal temperature and flowering in one species is novel. The predictive power of the models was validated through a jackknife sequential recalculation approach, revealing strong positive and negative predictive ability for flowering for four of the five species. Applications of the models include assisting in determination of the suitability of areas for vegetation restoration and identifying the possible effects of climate change on flowering in the study species.
  International Journal of Bioclimatology Biometeorology 01/2012; 56(1):95-105. · 2.25 Impact Factor
• Article: Floral visitation in the Australian native shrub genus Acrotriche R.Br (Ericaceae): an abundance of ants (Formicidae)

  Melanie Schneemilch, Craig Williams, Michael Kokkinn
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  ABSTRACT: The genus Acrotriche is a group of predominantly winter flowering Australian native plants with small flowers that use a unique method of secondary pollen presentation. The mating system of one species has been determined as requiring transfer of pollen from one plant to another to enable effective pollination and floral conformity in other species suggests similar breeding systems. Previous authors have suggested non-flying mammal pollination for members of the genus based on floral traits and reports of floral consumption; however, this hypothesis does not stand up to scrutiny. Acrotriche floral traits can also be interpreted as indicative of crawling invertebrate pollination. The identification of floral visitors and their potential for pollination has not been conducted previously for any Acrotriche species. To identify potential pollinators, the floral visitors to six different species of Acrotriche were observed throughout an entire 24 h period at a range of sites throughout South Australia. Ants were identified as the most common and abundant floral visitors for all Acrotriche species. Ant pollination is considered rare due to the negative effects that ant secretions can have on pollen viability. To determine these effects in relation to Acrotriche, pollen germination experiments were undertaken after contact with the integument of several ant species. Reductions in pollen viability varied between plants and ant species but in all experiments viable pollen remained after ant contact. These results, along with observed behaviour of ant visitors, indicate that ants may contribute to pollination in Acrotriche.
  Australian Journal of Entomology 01/2011; 50(2):130 - 138. · 0.97 Impact Factor