Walsh, Ryan , Michaels, Helen .
The Effects of Pollinator Limitation and Granivory on the Deceptive Orchid, Cypripedium candidum Muhl ex Willd. (Orchidaceae).
For many species of conservation significance, multiple factors limit reproduction. This research examines the contributions of pollinator attraction, pollen receipt, and granivory as limiting factors to reproduction in the White Lady's Slipper Orchid, Cypripedium candidum Muhl ex Willd. Cypripedium spp. require visitation by a suitable pollinator as the relatively complex floral anatomy prevents intra-flower selfing. However, C. candidum may produce 1-9 or more flowering stems that may be geitonogamously selfed. Increased floral display size may facilitate competition for pollinators, it may also lead to increased granivore attraction. Pollen limitation, granivory and reproductive trade-offs were examined in a field experiment in an unusually large population (n > 6000). Pairs of plants (n=36) were matched by number of flowering stems (1-6) and received either supplemental hand outcross or natural pollination. Capsule maturation, mass of seeds, and granivory rates were scored. Pollen supplementation significantly (p<0.0001) increased the percent of flowers setting mature fruit, with 87% fruit set for flowers receiving added pollen compared to only 46% for those only receiving natural pollinator service. Taller inflorescences had significantly higher initial and final fruit set (p = 0.028 and p = 0.049 respectively), although other measures of plant size (numbers of stems, leaves, and flowers) had no effect on female function. Total seed set was also limited by seed predation, with 73% of the capsules affected, while shorter stems were significantly (p=0.0017) more likely to be predated. Number of fruits and number of flowers had no effect on the probability of predation. Taller flowering stems had a significantly higher pollinia removal (p=0.001) while number of flowers and numbers of stems had no effect on pollinia removal. This study demonstrates evidence of pollinator limitation while highlighting the effects of plant height, display size and granivory on reproductive fitness in a highly modified deceptive breeding system.
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1 - Bowling Green State University, Department of Biological Sciences, Bowling Green, OH, 43403, USA
2 - BOWLING GREEN STATE UNIVERSTITY, Department Of Biological Sciences, Life Science Building, Bowling Green, OH, 43403, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Delaware D/Hyatt
Date: Wednesday, July 11th, 2012
Time: 2:30 PM