Sawyer, Neil W. .
Reproductive Ecology of Trillium recurvatum Beck (Trilliaceae).
Trillium recurvatum Beck is a long-lived perennial that is at its northernmost distributional range in southern Wisconsin, and is listed as Special Concern. The breeding system and reproductive ecology of this purple, sessile-flowered Trillium have not been previously studied. To test the hypothesis that pollen limitation, rather than its limited distributional range or habitat loss, is a primary, contributing factor to the rarity of T. recurvatum, its breeding system and reproductive ecology were studied. Pollinator activity, pollen to ovule ratios, fruit- and seed-set, and breeding system dynamics via field crossing studies were assessed. Observations of insect visitations revealed a single, effective pollinator, Coleomegilla maculata De Greer. The estimated pollen to ovule ratio was 3,255 to 1, strongly suggesting obligate out-crossing. Seeds were small, weighing less than any species in the genus. Fruit-set in hand-pollinated, out-crossed flowers was significantly greater than in open-pollinated controls, demonstrating pollen limitation. Autogamous crosses yielded no fruit-set, demonstrating self-incompatibility. Seed-set was greater in open-pollinated controls than in manipulated flowers, indicating high pollen load depositions. This study demonstrates that pollen limitation is present in T. recurvatum but loss of habitat, habitat fragmentation, and effects of distributional range limitation may not be discounted as forces influencing its rarity.
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1 - University of Wisconsin Whitewater, Biological Sciences, 800 West Main Street, Whitewater, Wisconsin, 53190, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 1:30 PM