Davila, Yvonne C , Wardle, Glenda M .
Does geographic, annual and diurnal variation in pollinator visitation define a generalist-pollinated plant?
Insects pollinate up to 90% of angiosperm species worldwide, with many plants relying on several pollinators (generalists). Variation in pollinator types among and within flowering seasons, and throughout the day often occurs. In widespread plant species, the taxonomic composition of the pollinator assemblage may vary among populations across the geographic range. In addtion, populations and plants within populations may not be equally generalist, receiving pollination services from various pollinator types. Few studies have addressed how spatial and temporal variation in pollinators may affect mating in plants, particularly generalist pollination systems. We assessed the diurnal and nocturnal insects visiting Trachymene incisa (Apiaceae), a widespread Australian herb, to determine spatial and temporal variation in insect visitation rates and assemblage composition. In addition, we explore how this variation may relate to reproductive output. Most insect visits were recorded between 0900h and 1630h. Native bees, flies and ants were common visitors, with butterflies and beetles less common. Visitation rates varied significantly throughout the day, with a peak during midday. A significant population by year interaction was driven by an increase in insect visitation at Myall Lakes and a decrease in insect visitation at Tomago over consecutive years. The insect assemblage also varied among populations and years, the most notable being a shift from predominantly ant visits in 2003 to mostly bee and fly visits in 2004 at Agnes Banks. The proportion of seeding umbels per plant, percentage seed set per umbel and percentage final emergence of seedlings also varied among populations in 2003. The Apiaceae are considered to be highly generalist in terms of pollination, although variation in pollinators is likely to affect reproductive output. This study also highlights that the pollinators of a generalist-pollinated plant species cannot be completely determined from observations at a single time of the day, population or year.
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1 - The University of Sydney, Institute of Wildlife Research and School of Biological Sciences, Heydon-Laurence Building, A08, The University of Sydney, Sydney, New South Wales, 2006, Australia
spatial and temporal variation.
Presentation Type: Oral Paper
Location: Salon A - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 3:00 PM