Wild and managed bees are well 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.unmanaged pollinator | insect pollinator | fly | bee | beetle

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Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield–related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

It has been debated whether pollination success in nonrewarding plants that flower in association with nectar‐producing plants will be diminished by competition for pollinator visits or, alternatively, enhanced through increased local abundance of pollinators (the magnet species effect). We experimentally evaluated these effects using the nonrewarding bumblebee‐pollinated orchid Anacamptis morio and associated nectar‐producing plants at a site in Sweden. Pollination success (estimated as pollen receipt and pollen removal) in A. morio was significantly greater for individuals translocated to patches of nectar‐producing plants (Geum rivale and Allium schoenoprasum) than for individuals placed outside (∼20 m away) such patches. These results provide support for the existence of a facilitative magnet species effect in the interaction between certain nectar plants and A. morio. To determine the spatial scale of these interactions, we correlated the visitation rate to flowers of A. morio with the density of sympatric nectar plants in 1‐m2 and 100‐m2 plots centered around groups of translocated plants, and at the level of whole meadows (∼0.5–2 ha). Visitation rate to flowers of A. morio was not correlated with the 1‐m2 patch density of G. rivale and A. schoenoprasum, but showed a significant positive relationship with density of these nectar plants in 100‐m2 plots. In addition, visitation to flowers of A. morio was strongly and positively related to the density of A. schoenoprasum at the level of the meadow. Choice experiments showed that bees foraging on the purple flowers of A. schoenoprasum (a particularly effective magnet species) visit the purple flowers of A. morio more readily (47.6% of choices) than bees foraging on the yellow flowers of Lotus corniculatus (17% of choices). Overall similarity in flower color and shape may increase the probability that a pollinator will temporarily shift from a nectar‐producing “magnet” plant to a nonrewarding plant. We discuss the possibility of a mimicry continuum between those orchids that exploit instinctive food‐seeking behavior of pollinators and those that show an adaptive resemblance to nectar‐producing plants.

NILSSON, L. A., 1983. Processes of isolation and introgressive interplay between Platanthera bifolia L. Rich, and P. chlorantha (Custer; Reichb. (Orchidaceae). Platanthera bifolia and P. chlorantha are highly specialized for pollination by crepuscular and nocturnal Lepidoptera. The plants are largely sympatric, have overlapping flowering‐times, and are completely interfertile. Principal differences exist in floral fragrance and column morphology. Isolation is effected by a set of integrated morphological, ethological, and seasonal mechanisms. Odour‐based constancy by moths, differences in column structure, attachment of pollinaria, spurlength, nectar availability, and flowering‐peaks reduce interspecific pollen transfer. The plants form a functional species pair in relation to their pollination environment and locally share the same main pollinator species. Hybrids, which infrequently occur in areas of sympatry, emit a blend of the species‐specific fragrance compounds and have intermediate column structure. They are frequently visited by‐moths but suffer a serious reduction in seed production due to imperfect interaction vis‐à‐vis the pollen vectors. Hybrid viscidia, in an intermediate position on the column, are touched by moths' scaly and hairy palps and get insufficient attachment, evidently causing hybrids to act solely as female recipient. First backcross individuals largely join the functional range of either species which promotes rapid introgression. The two gene‐pools interplay, although always at a low level. Patterns of introgressive hybridization were exemplified.