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Species turnover promotes the importance of bee diversity for crop pollination at regional scales

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Science  16 Feb 2018:
Vol. 359, Issue 6377, pp. 791-793
DOI: 10.1126/science.aao2117
  • Fig. 1 How the number of bee species needed to provide pollination changes with increasing spatial extent.

    (A) A typical graph from a biodiversity-function experiment shows that a certain number of species (x) is needed to achieve a given level of function (w) within one community. (B) By contrast, studying ecosystem services at large scales requires analyses across communities. The threshold level of function w is now implicit, and the cumulative number of species required to achieve function level w at all n communities is plotted as a function of increasing spatial extent. In this example, x species are needed to provide function level w in one community, and y species are needed to provide function level w in each of n communities across an entire landscape. (C) Commercial crop fields of watermelon (green triangles), cranberry (red circles), and blueberry (blue squares) in New Jersey and Pennsylvania, USA, where bee biodiversity and crop pollination were measured. (D) Cumulative number of bee species required to maintain thresholds of 25% (orange), 50% (black), and 75% (purple) of the mean observed level of pollination, at each of n sites (16). Horizontal dashed lines indicate the total number of bee species observed in each study. Error bars represent 1 SD over all possible starting sites for expanding the spatial extent. For all three crops combined, each x-axis increment represents the addition of one site per crop.

  • Fig. 2 How species turnover and dominance determine the number of species required for ecosystem services.

    (A) Conceptual diagram showing how observations (black; as in Fig. 1D) could be compared with a null model (red) that assumes each species in a community contributes the same amount of ecosystem services. D represents the effect of dominance in the absence of turnover (i.e., at only one site). T denotes the effect of turnover in the absence of dominance. T|D represents the effect of turnover in the presence of dominance, thus matching data as observed in the field. D|T is the effect of dominance in the presence of turnover (i.e., the number of additional species that would be needed in the absence of dominance). (B) Same as (A), but showing how the relative contribution of T|D increases with increasing spatial scale (blue arrows), whereas that of D|T may not (green arrows). (C) Observed data from this study (black) plotted against the null model (red), as in (A). Green and blue arrows are as in (B); horizontal dashed lines are conceptually the same as those in (A) and (B) (i.e., the lines show baseline values at number of sites = 1). Data were plotted for the 50% threshold.

Supplementary Materials

  • Species turnover promotes the importance of bee diversity for crop pollination at regional scales

    Rachael Winfree, James R. Reilly, Ignasi Bartomeus, Daniel P. Cariveau, Neal M. Williams, Jason Gibbs

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods 
    • Figs. S1 to S5
    • Tables S1 and S2
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