Thesis

Sex allocation in Lloydia serotina, an androdioecious alpine lily

According to sex allocation theory and evolutionarily stable strategy models, several characteristics, including a greater than twofold increase in male fitness, are required for functional androdioecy. Lloydia serotina (Liliaceae ), a morphologically androdioecious alpine lily, exhibits most of these characteristics: populations contain many more hermaphrodites than males and both sexes produce viable pollen. Pollen production is roughly equal between sexes, however, so the increase in fitness in males is not due to pollen production. To determine whether alternative variables could account for enhanced fitness in males, populations of L. serotina were studied in Olympic National Park and Niwot Ridge Biosphere Reserve using both observational and manipulative experiments. Bulb size was significantly larger in males than in both hermaphrodite and non-flowering plants, suggesting the possibility that males flower more frequently. Manipulative experiments comparing resource allocation patterns suggested that males allocate more of their post-maintenance energy to clonal reproduction early in the growing season. Thus, trade-offs in vegetative versus sexual reproduction may increase fitness in males when pollen production cannot. Males may be maintained in populations of L. serotina because they devote resources not used for female function to vegetative reproduction while retaining full male function, thus increasing the males' fitness component. These factors may create the necessary twofold increase in fitness in males required to maintain them over evolutionary time.

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