Abstract Detail

Ecological Section

Cane, James [1], Schiffhauer, Dan [2].

Refining estimates of pollinator efficiencies calculated from delivered stigmatic loads: a cranberry model.

Forbs pollinated by bees typically attract guilds of diverse species. They often differ in pollination efficacy, measured as mean pollen deposition o­n stigmas, fruit set, or seed set, that results from single floral visits. Raw counts of stigmatic pollen loads do not directly correspond to fruit and seed set, however. To refine estimates of pollinator efficacy using stigmatic pollen loads, a model system was developed using the American cranberry. In the greenhouse, individual floral stigmas were manually loaded with known counts of pollen grains; subsequent berry size and fruit and seed set were later scored. Fruiting and seed set responses were regressed o­n to stigmatic pollen load. Four bee species were then compared for delivered stigmatic pollen loads, comparing raw counts of deposited pollen with predicted fruit and seed set. Differences waned between several bee species when compared for predicted fruit or seed set, because some species delivered pollen loads in excess of asymptotic needs. Others were found to be adequate pollinators, for although they typically delivered few pollen grains, we found that o­nly a few pollen grains are in fact needed to set fully sized fruits. Shortcuts to estimate these thresholds and asymptotes for fruit and seed set response to stigmatic load are explored.

1 - USDA-ARS, Bee Biology and Systematics Laboratory, Utah State University, Logan, Utah, 84322-5310, USA
2 - Ocean Spray Cranberries Inc., Marucci Blueberry/Cranberry Research Center, Chatsworth, New Jersey, 08019, USA

Keywords:
pollination
Ericaceae
seed mass
fruit set
stigmatic loading
Vaccinium
bees
guild
pollinator efficacy.

Presentation Type: Paper
Session: 17-2
Location: Wasatch (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 1:30 PM
Abstract ID:156