Fears of a Decline in Bee Pollination Confirmed
ScienceDaily (Sep. 7, 2010) — Widespread reports of a decline in the population of bees and other flower-visiting animals have aroused fear and speculation that pollination is also likely on the decline. A recent University of Toronto study provides the first long-term evidence of a downward trend in pollination, while also pointing to climate change as a possible contributor.
A recent study provides the first long-term evidence of a downward trend in pollination. (Credit: iStockphoto)
"Bee numbers may have declined at our research site, but we suspect that a climate-driven mismatch between the times when flowers open and when bees emerge from hibernation is a more important factor," says James Thomson, a scientist with U of T's Department of Ecology and Evolutionary Biology.
Thomson's 17-year examination of the wild lily in the Rocky Mountains of Colorado is one of the longest-term studies of pollination ever done. It reveals a progressive decline in pollination over the years, with particularly noteworthy pollination deficits early in the season. The study will be published inPhilosophical Transactions of the Royal Society B: Biological Sciences on September 6.
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Flowering phenology, fruiting success and progressive deterioration of pollination in an early-flowering geophyte
James D. Thomson1,2,3,*
-Author Affiliations
1Department of Ecology and Evolutionary Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
2Rocky Mountain Biological Laboratory, PO Box 519, Crested Butte, CO 81224, USA
3Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794, USA
*james.thomson@utoronto.ca
Abstract
Spatio-temporal patterns of snowmelt and flowering times affect fruiting success in Erythronium grandiflorum Pursh (Liliaceae) in subalpine western Colorado, USA. From 1990 to 1995, I measured the consistency across years of snowmelt patterns and flowering times along a permanent transect. In most years since 1993, I have monitored fruit set in temporal cohorts (early- to late-flowering groups of plants) at one site. To assess ‘pollination limitation’, I have also conducted supplemental hand-pollination experiments at various times through the blooming season. The onset of blooming is determined by snowmelt, with the earliest years starting a month before the latest years owing to variation in winter snowpack accumulation. Fruit set is diminished or prevented entirely by killing frosts in some years, most frequently but not exclusively for the earlier cohorts. When frosts do not limit fruit set, pollination limitation is frequent, especially in the earlier cohorts. Pollination limitation is strongest for middle cohorts: it tends to be negated by frost in early cohorts and ameliorated by continuing emergence of bumble-bee queens in later cohorts. This lily appears to be poorly synchronized with its pollinators. Across the years of the study, pollination limitation appears to be increasing, perhaps because the synchronization is getting worse.
Bombus climate change Erythronium frost phenological synchrony pollinator decline
Footnotes
One contribution of 11 to a Theme Issue ‘The role of phenology in ecology and evolution’.
© 2010 The Royal Society
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