Smith-Huerta, Nancy , Freeman, Charlotte , Huerta, Alfredo .
Pollen-ovule ratios vary with breeding system in the California wildflower Clarkia tembloriensis (Onagraceae).
Pollen-ovule ratios are known to vary with mating system, with selfing taxa possessing smaller ratios than outcrossers. Sex allocation theory predicts that there are tradeoffs between investments in reproductive male and female functions. The nature of these tradeoffs is predicted to vary with the breeding system of a plant. Selfing taxa are predicted to have relatively small and stable pollen-ovule ratios across populations. However, outcrossing taxa are predicted to have greater variability and higher pollen-ovule ratios (Mazer et al., 2007. Evolution 61:83-98). Populations of the California wildflower Clarkia tembloriensis, provide an excellent opportunity to test these predictions since the species consists of populations which vary in flower size and breeding system. Populations of this species fall into three types; Plants with 1) Large, strongly protandrous outcrossing flowers, 2) Small protandrous outcrossing flowers, and 3) Small selfing non-protandrous selfing flowers. Pollen-ovule ratios and seed set were determined for four of these populations which vary with respect to these characters. Ovule numbers were significantly greater in the protandrous outcrossing flowers (both small and large flowers) than in small selfing flowers. Pollen numbers were greatest in the large-flowered protandrous outcrossing flowers, less in the small-flowered protandrous outcrossing flowers, and least in the small-flowered selfers . Pollen-Ovule ratios were highest for the large-flowered outcrossers, less for the small-flowered outcrossers, and least for the selfing population. Seed set was greatest for the large-flowered outcrossers, less for the small-flowered outcrossers, and least for the small-flowered selfers. The variation in pollen-ovule ratios observed between the different outcrossing populations in this study supported the predictions made by sexual allocation theory as stated above.
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1 - Miami University, Department Of Botany, 316 Pearson Hall, Department Of Botany, Oxford, OH, 45056, USA
2 - Miami University, Department of Botany, Oxford, OH, 45056
3 - Miami University, Department Of Botany, Oxford, OH, 45056, USA
Presentation Type: Poster:Posters for Topics
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM