PARENT SESSION
Oral Session # 34: Plant Ecology II: Pollination and Dispersal.
Presiding: A McEuen
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 202.
Nectar sugar composition and quantities in insect-pollinated Midwestern spring herbs.
Dailey, Theresa*,1, Scott, Peter1, Liu, Xiao-Chuan1, 1 Indiana State University, Terre Haute, IN
ABSTRACT- To compare the nectar resources offered to flies and small, solitary bees by native flowers and exotic weeds, we studied the woodland flowers Erigenia bulbosa, Claytonia virginica, and Cardamine concatenata and the agricultural weeds Stellaria media and Barbarea vulgaris. One-day nectar accumulations in covered, unvisited flowers were analyzed via high performance liquid chromatography (HPLC) to determine sugar identity. Sugar quantities were determined from HPLC data and large additional samples (40 flowers per species per day) were analyzed by spectrophotometry. Fructose, present in 85-100% of all samples, was the most commonly found sugar in all species, and was used in making standards for spectrophotometry. Glucose and/or sucrose were found in each species, but never consistently. Despite the tiny quantities and multi-step measurement process, we obtained repeatable mean nectar sugar accumulations for each species. Erigenia bulbosa and Stellaria media (means = 24 and 32 micrograms) offered the smallest amounts of sugar, while Cardamine concatenata (mean = 172 micrograms) offered the largest. Claytonia virginica and Barbarea vulgaris offered similar amounts of sugar (means = 78 and 80 micrograms). Thus, both habitats had a low-reward and a moderate-reward flower. The most rewarding flower was a woodland species, but it was less common than the other 4 species. This suggests that per-flower nectar rewards in midwestern woodlands and adjacent agricultural fields may be similar in spring.
Key words: flower, nectar