HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Data Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ivey, C. T. Articles by Wyatt, R. Search for Related Content PubMed Articles by Ivey, C. T. Articles by Wyatt, R. Agricola Articles by Ivey, C. T. Articles by Wyatt, R.

Variation in pollinator effectiveness in swamp milkweed, Asclepias incarnata (Apocynaceae)¹

²Blandy Experimental Farm, University of Virginia, 400 Blandy Farm Lane, Boyce, Virginia 22620 USA; ³6387 Brookstone Boulevard, Columbus, Georgia 31904 USA; ⁴Highlands Biological Station, P.O. Box 580, Highlands, North Carolina 28741 USA

The contribution of a pollinator toward plant fitness (i.e., its "effectiveness") can determine its importance for the plant's evolutionary ecology. We compared pollinators in a population of Asclepias incarnata (Apocynaceae) for several components of pollinator effectiveness over two flowering seasons to evaluate their importance to plant reproduction. Insects of the order Hymenoptera predominate in A. incarnata pollination, but there appears to be no specialization for pollination within this order. Pollinators varied significantly in nearly every component of effectiveness that we measured, including pollen load, removal and deposition of pollen, pollination efficiency (deposition/removal), flower-handling time, and potential for geitonogamy (fractional pollen deposition). The visitation rate of pollinators also varied significantly between years and through time within years. Pollination success and percentage fruit-set of unmanipulated plants in the population also varied significantly between years, and pollination success varied among sample times within years. Most components of effectiveness were weakly correlated, suggesting that the contributions of visitor species toward pollination varied among effectiveness components. Mean flower-handling time, however, was strongly correlated with several components, including pollen removal and deposition, pollination efficiency, and fractional pollen deposition. These findings highlight the significance of pollination variability for plant reproduction and suggest that time-dependent foraging behaviors may play an important role in determining pollinator effectiveness.

Key Words: Apocynaceae • Asclepias incarnata • flower-handling time • fractional pollen deposition • geitonogamy • generalization • plant reproductive success • pollination • pollinator effectiveness • specialization

This article has been cited by other articles:

				Y. Matsuki, R. Tateno, M. Shibata, and Y. Isagi Pollination efficiencies of flower-visiting insects as determined by direct genetic analysis of pollen origin Am. J. Botany, August 1, 2008; 95(8): 925 - 930. [Abstract] [Full Text] [PDF]

				H. J. Young, D. W. Dunning, and K. W. v. Hasseln Foraging behavior affects pollen removal and deposition in Impatiens capensis (Balsaminaceae) Am. J. Botany, July 1, 2007; 94(7): 1267 - 1271. [Abstract] [Full Text] [PDF]

				J. J. Fumero-Caban and E. J. Melendez-Ackerman Relative pollination effectiveness of floral visitors of Pitcairnia angustifolia (Bromeliaceae) Am. J. Botany, March 1, 2007; 94(3): 419 - 424. [Abstract] [Full Text] [PDF]

				H. F. Sahli and J. K. Conner Visitation, effectiveness, and efficiency of 15 genera of visitors to wild radish, Raphanus raphanistrum (Brassicaceae) Am. J. Botany, February 1, 2007; 94(2): 203 - 209. [Abstract] [Full Text] [PDF]

				J. D. Karron, R. J. Mitchell, and J. M. Bell Multiple pollinator visits to Mimulus ringens (Phrymaceae) flowers increase mate number and seed set within fruits Am. J. Botany, September 1, 2006; 93(9): 1306 - 1312. [Abstract] [Full Text] [PDF]

				L. S. ADLER and R. E. IRWIN Comparison of Pollen Transfer Dynamics by Multiple Floral Visitors: Experiments with Pollen and Fluorescent Dye Ann. Bot., January 1, 2006; 97(1): 141 - 150. [Abstract] [Full Text] [PDF]

				I. Dohzono, K. Suzuki, and J. Murata Temporal changes in calyx tube length of Clematis stans (Ranunculaceae): a strategy for pollination by two bumble bee species with different proboscis lengths Am. J. Botany, December 1, 2004; 91(12): 2051 - 2059. [Abstract] [Full Text] [PDF]