Non-bee insects are important contributors to global crop pollination

Wild andmanaged bees arewell documented as effective pollinators of global crops of economic importance. However, the contributions by pollinators other than bees have been little explored despite their potential to contribute to crop production and stability in the face of environmental change. Non-bee pollinators include flies, beetles, moths, butterflies, wasps, ants, birds, and bats, among others. Here we focus on non-bee insects and synthesize 39 field studies from five continents that directly measured the crop pollination services provided by non-bees, honey bees, and other bees to compare the relative contributions of these taxa. Non-bees performed 25-50% of the total number of flower visits. Although non-bees were less effective pollinators than bees per flower visit, they made more visits; thus these two factors compensated for each other, resulting in pollination services rendered by non-bees that were similar to those provided by bees. In the subset of studies that measured fruit set, fruit set increased with non-bee insect visits independently of bee visitation rates, indicating that non-bee insects provide a unique benefit that is not provided by bees. We also show that non-bee insects are not as reliant as bees on the presence of remnant natural or seminatural habitat in the surrounding landscape. These results strongly suggest that non-bee insect pollinators play a significant role in global crop production and respond differently than bees to landscape structure, probably making their crop pollination services more robust to changes in land use. Non-bee insects provide a valuable service and provide potential insurance against bee population declines.Peer Reviewe

Oxidized and reduced Azotobacter vinelandii ferredoxin I at 1.4 A resolution: conformational change of surface residues without significant change in the [3Fe-4S]+/0 cluster

The refined structure of reduced Azotobacter vinelandii 7Fe ferredoxin FdI at 100 K and 1.4 A resolution is reported, permitting comparison of [3Fe-4S]+ and [3Fe-4S]0 clusters in the same protein at near atomic resolution. The reduced state of the [3Fe-4S]0 cluster is established by single-crystal EPR following data collection. Redundant structures are refined to establish the reproducibility and accuracy of the results for both oxidation states. The structure of the [4Fe-4S]2+ cluster in four independently determined FdI structures is the same within the range of derived standard uncertainties, providing an internal control on the experimental methods and the refinement results. The structures of the [3Fe-4S]+ and [3Fe-4S]0 clusters are also the same within experimental error, indicating that the protein may be enforcing an entatic state upon this cluster, facilitating electron-transfer reactions. The structure of the FdI [3Fe-4S]0 cluster allows direct comparison with the structure of a well-characterized [Fe3S4]0 synthetic analogue compound. The [3Fe-4S]0 cluster displays significant distortions with respect to the [Fe3S4]0 analogue, further suggesting that the observed [3Fe-4S]+/0 geometry in FdI may represent an entatic state. Comparison of oxidized and reduced FdI reveals conformational changes at the protein surface in response to reduction of the [3Fe-4S]+/0 cluster. The carboxyl group of Asp15 rotates ∼90°, Lys84, a residue hydrogen bonded to Asp15, adopts a single conformation, and additional H2O molecules become ordered. These structural changes imply a mechanism for H+ transfer to the [3Fe-4S]0 cluster in agreement with electrochemical and spectroscopic results