The Evolution and Maintenance of Mixed Mating Systems
Karron, Jeffrey , Mitchell, Randy , Holmquist, Karsten .
Pollinator visitation history strongly influences among-flower variation in selfing rates and mate number.
Species with mixed-mating systems often show marked variation in mating patterns within and among populations. Such variation may even be present among flowers on an individual floral display. We tested the hypothesis that among-flower variation in selfing rates and mate number reflects the visitation history of individual flowers. On multi-flower displays pollinators often probe several flowers consecutively on a plant. Although the first flower probed is likely to receive substantial outcross pollen, if pollen carryover is limited receipt of self pollen would increase rapidly for later flowers. In experimental arrays of Mimulus ringens (monkeyflower), selfing rates increased significantly with successive probes on multi-flowered plants. The first flower probed typically had a selfing rate of 0-20%. By contrast, the fourth flower probed typically had a selfing rate of 80-100%. This is the first direct demonstration that consecutive geitonogamous probes increase selfing rates. The number of outcross mates also varies markedly among Mimulus ringens fruits, ranging from 0 to 9 fathers. We hypothesized that sequential probes increase the number of sires per fruit by depositing pollen from donors not represented in the initial probe. We compared the extent of multiple paternity in flowers probed a single time and flowers probed three or more times. Flowers receiving a single probe averaged 3.12 outcross sires per fruit, indicating that single probes deposit pollen from several donors. Multiple paternity was even higher following multiple probes, averaging 4.92 outcross sires per fruit. These results indicate that the unique visitation history of individual flowers may dramatically influence mating patterns and is likely to play an important role in the evolution of mixed mating systems.
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1 - University of Wisconsin Milwaukee, Department of Biological Sciences, Lapham Hall, Po Box 413, Milwaukee, Wisconsin, 53201, USA
2 - University of Akron, Department of Biology, Akron, Ohio, 44320-3908, USA
3 - University of Wisconsin, USDA Vegetable Crops Research Unit, 1575 Linden Drive, Madison, WI, 53706
Presentation Type: Symposium or Colloquium Presentation
Location: Stevens 5/Hilton
Date: Monday, July 9th, 2007
Time: 11:15 AM