The Evolution and Maintenance of Mixed Mating Systems
Chang, Shu-Mei .
Maintenance of females in a gynodioecious geranium, Geranium maculatum.
Gynodioecy is a breeding system in which female and hermaphroditic plants of the same species coexist in a population. Mixed mating is facilitated in gynodioecious species because females can only outcross while hermaphrodites can both self and outcross. Females in gynodioecious populations are generally considered to be at a disadvantage compared to hermaphrodites because females can only reproduce through seeds, have smaller flowers and are therefore less attractive to pollinators, and are more likely to be pollen limited when pollinators are scarce. Theories predict that, in order to coexist with hermaphrodites, females need to produce more and/or better seeds, a phenomenon often referred to as female compensation. I carried out field studies using populations of a gynodioecious wild geranium, Geranium maculatum, that support this view. In addition, I have used field and greenhouse experiments to test three mechanisms proposed to be responsible for female compensation: resource re-allocation, physiological difference and inbreeding depression. I found little evidence for the resource reallocation and physiological difference hypotheses. In contrast, differential rates of inbreeding (selfing and/or biparental inbreeding) coupled with inbreeding depression are likely to be an important factor contributing to female compensation in this species. Results from these experiments will be reported and discussed in the context of maintaining a mixed mating system in Geranium maculatum.
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1 - Dept of Plant Biology, University of Georgia, Athens, GA, 30602, USA
mixed mating systems.
Presentation Type: Symposium or Colloquium Presentation
Location: Stevens 5/Hilton
Date: Monday, July 9th, 2007
Time: 10:15 AM