Klips, Robert , Lin, Chia-Hua .
Pollinator visitation of co-flowering prairie milkweeds and a method to assess the effect of clone size on outcross pollination rates.
Sullivant’s milkweed (Asclepias sullivantii; Apocynaceae) is an uncommon perennial herb with a high fidelity to prairies that often occurs along with the widespread common milkweed (A. syriaca) in disturbed prairie remnants. Both are self-incompatible clonal plants generally regarded as being adapted for pollination by a diverse array of hymenopteran and lepidopteran generalist flower visitors. Their flowering periods broadly overlap. Self-incompatible milkweeds have a late-acting incompatibility mechanism that can preclude fertilization by outcross pollinia received after self pollinia. Therefore, milkweeds may be especially susceptible to the “clonal paradox,” wherein multi-stemmed large clones experience a reduction in per-stem reproductive output owing to the delivery of a preponderance of self pollen from the same clone through short-distance pollinator foraging. Using digital video cameras trained on fully flowering umbels of both species for 15-minute intervals throughout the blooming season, we assayed visitation to both species by foraging large bees. We developed a method using microsatellite markers to determine whether clone size might influence the proportion of self pollinia carried by foraging pollinators. We screened a total of 18 previously published Asclepias microsatellite primers that could be used to differentiate clones using DNA extracted from leaf tissues and individual pollinia. Visitation rates and pollinator assemblages varied markedly for the two milkweed species.
For A. syriaca (14 intervals analyzed), the average number of visits during the 15-minute periods was 8.0 (SD 4.23, range 1-18), of which 53.1% of visits were by Apis mellifera, 39.8% by Bombus, and 7.1% by Xylocopa virginica. The Asclepias sullivantii umbels (15 intervals analyzed) had a much higher total visitation rate of 44.6 visits (SD 16.35, range 21-81) which were much more honeybee-dominated, having proportions of 99.0% Apis and less than 1.0% Bombus and Xylocopa. Among the 18 microsatellite primers surveyed, 6 were found to be highly polymorphic (multilocus probability of random identity <0.002) and amenable to PCR amplification in multiplex combination, yielding loci sufficiently different in length to be resolved together using a capillary sequencer. Thereby, individual pollinia can, despite their having a low genome copy-number content, be genotyped in one reaction using a simple high throughput extraction protocol.
Log in to add this item to your schedule
1 - Ohio State University, Evolution, Ecology And Organismal Biology, 1465 MT VERNON AVE, MARION, OH, 43302, USA
2 - Ohio State University , Evolution, Ecology and Organismal Biology, 318 W 12th Avenue , Columbus, OH, 43212, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Delaware D/Hyatt
Date: Wednesday, July 11th, 2012
Time: 3:00 PM