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The effect of maternal phenology on offspring characters in the herbaceous plant Campanula americana

Authors


Laura F. Galloway, Department of Biology, University of Virginia, Charlottesville VA, 22904-4328, USA (tel. +1 434 982 5010, fax +1 434 982 5626, e-mail: lgalloway @virginia.edu).

Summary

  • 1An individual's phenotype may influence the expression of traits in its offspring. I tested whether maternal flowering phenology influenced offspring germination and thus life history schedule in two populations of Campanula americana. Autumn-germinating C. americana grow as annuals whereas individuals that germinate in the spring are biennials.
  • 2Under near-natural conditions, early-season flowers produced seeds that were more likely to germinate in the autumn than late-season flowers, but spring germination was equally likely for all seeds.
  • 3Seed mass (two of three years) and percentage and timing of germination under constant environmental conditions (all three years) did not vary across the reproductive season. External environmental factors are therefore more likely to contribute to seasonal changes in the probability of germinating in the autumn than are the characteristics of the seeds.
  • 4The frequency of annual offspring varied among maternal plants. The association between the time a flower was open and offspring germination season suggests that evolution of life history schedule may be accomplished by altering maternal flowering phenology.
  • 5The association between the time of a flower's anthesis and its fruit maturation was weaker in two years when water was limiting. Limited water also resulted in earlier seed maturation, and consequently a greater proportion of a population's seed being produced during the period when autumn germination was likely. This, in combination with differences between populations, suggests that the magnitude of maternal phenological effects varies across years and populations.

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