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Reproductive ecology of five species of Australian Alpine Ranunculus

C. Pickering

Published 1994 in Journal and proceedings of the Royal Society of New South Wales

ABSTRACT

This study examines current hypotheses in plant reproductive ecology concerning proximate and ultimate factors that may affect two critical stages of reproduction: seed production and flowering. Based on the results obtained from testing these hypotheses, models are proposed for the overall reproductive strategies of the species examined (alpine Ranunculus) and other herbaceous perennials. The initial stage in testing these hypotheses involved characterising the breeding systems and flowering phenology of Ranunculus muelleri, R. dissectifolius, R. graniticola, R. millanii, and R. niphophilus over two flowering seasons at two sites in the Australian alpine region. All five species are facultatively xenogamous. Flowers appear to promote outcrossing by partial protogyny. Ranunculus dissectifolius and R. graniticola are partially self-compatible, and R. muelleri, R. millanii and R. niphophilus are fully self-compatible. The transfer of pollen within a flower by thrips or mechanical means occurred in all species and for most species seed set was not limited by within flower pollen transfer. The five species differed in plant size, number of flowers, number of anthers, ovules and seed per flower and per plant, the date on which plants commenced flowering, duration of flowering, asynchrony of flower production, and synchrony with conspecifics. Limitation of seed set by fertilization was investigated by the experimental manipulation of flowers in the field. Seed set was not limited by fertilization in R. graniticola; was only limited at one time during the flowering season in R. millanii; was slightly limited by the amount of pollen transferred by pollinators in R. muelleri and R. niphophilus; and was significantly limited by fertilization only in R. dissectifolius. The last was due either to pollinators transferring too few pollen grains, or not enough outcross pollen. For all species, seed set averaged below 60% even when outcross pollen was provided in abundance. Limitation of seed set by availability of resources in the field was investigated in R. muelleri, R. dissectifolius, R. graniticola and R. niphophilus by adding nutrients; by removing all but the first flower on a plant; or by removing half the leaves from plants in the field. Nutrient addition had no effect on seed set in any of the species. Removal of flowers increased seed set of the first flower only on R. dissectifolius plants. Leaf removal reduced the seed set by the first flower only on R. dissectifolius plants. It had no effect on seed set for plants for any of the four species. These results indicate that immediate resource availability is, in general, not limiting seed set in these four specie . The effect of plant size on various aspects of reproduction was examined in R. muelleri, R. dissectifolius, R. graniticola and R. niphophilus. All the results indicate that the main factor controlling the amount of seed produced by these Ranunculus species was the size of the plant, with the number of seed produced by a plant being proportional to the number of leaves. In these species bigger plants produced more

PUBLICATION RECORD

  • Publication year

    1994

  • Venue

    Journal and proceedings of the Royal Society of New South Wales

  • Publication date

    1994-06-01

  • Fields of study

    Biology, Environmental Science

  • Identifiers
    DOI 10.25911/5D6F9B2B94C10
  • External record

    Open on Semantic Scholar

  • Source metadata

    Semantic Scholar

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