Elevational Distribution of Insect Pollinators

Abstract

-Based on data from a wide range of locations, including two elevationally distinct sites in Utah, a generalized distribution pattern in the relative importance of various insect taxa as pollinators along elevational gradients emerged. In terms of relative species richness, hymenopterans are generally the dominant pollinators in lowland communities, but yield dominance at higher elevations to lepidopterans or, more often, to dipterans, which usually dominate the pollinator fauna at the highest elevations. Coleopterans are seldom of major significance as pollinators and generally decline in relative species richness as elevation increases. The observed trends for hymenopterans, dipterans and coleopterans have analogous counterparts among foliage insects, suggesting that the distributional patterns are a consequence of life history and thermoregulatory factors rather than selective pressures exerted by changes in flower structure along an elevational gradient. A lack of a generalized distribution pattern among lepidopteran pollinators may indicate that the thermoregulatory factors are less important in determining the elevational distribution of that taxon.