Patterns of widespread decline in North American bumble bees

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Bumble bees (Bombus) are vitally important pollinators of wild plants and agricultural crops worldwide. Fragmentary observations, however, have suggested population declines in several North American species. Despite rising concern over these observations in the United States, highlighted in a recent National Academy of Sciences report, a national assessment of the geographic scope and possible causal factors of bumble bee decline is lacking. Here, the authors report results of a three-year interdisciplinary study of changing distributions, population genetic structure, and levels of pathogen infection in bumble bee populations across the United States. They compare current and historical distributions of eight species, compiling a database of >73,000 museum records for comparison with data from intensive nationwide surveys of >16,000 specimens. They show that the relative abundances of four species have declined by up to 96% and that their surveyed geographic ranges have contracted by 23–87%, some within the last 20 years. Also shown is that declining populations have significantly higher infection levels of the microsporidian pathogen Nosema bombi and lower genetic diversity compared with co-occurring populations of the stable (nondeclining) species. Higher pathogen prevalence and reduced genetic diversity are, thus, realistic predictors of these alarming patterns of decline in North America, although cause and effect remain uncertain. Six pages of supporting information explain methods used for the three-year study: contemporary field surveys of U.S. bumble bees, U.S. bumble bee natural history collection database, statistical niche models, comparisons of historical and contemporary collections, pathogen screening, and genetic analysis. One figure and 9 tables can be downloaded to illustrate and tabulate findings.

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ELECTRONIC FILE - Zoology: Invertebrates

SWAP (2/19/2016) citation :
Cameron SA, Lozier JD, Strange JP, Koch JB, Cordes N, Solter LF, Griswold TL. 2011. Patterns of widespread decline in North American bumble bees. [accessed 2015 Jun 1]; Proceedings of the National Academy of Sciences. 108(2):662–667. http://www.pnas.org/content/108/2/662.full.pdf+html.

Generic citation: Cameron, S. A., J. D. Lozier, J. P. Strange, J. B. Koch, N. Cordes, L. F. Solter, T. L. Griswold. 2011. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Sciences of the United States of America 108(2):662-667. Available at: http://www.pnas.org/content/108/2/662.full.pdf+html, with supporting information at: http://www.pnas.org/content/suppl/2011/01/03/1014743108.DCSupplemental).