Predicting bee community responses to land-use changes: Effects of geographic and taxonomic biases

Land-use change and intensification threaten bee populations worldwide, imperilling pollination services. Global models are needed to better characterise, project, and mitigate bees' responses to these human impacts. The available data are, however, geographically and taxonomically unrepresentative; most data are from North America and Western Europe, overrepresenting bumblebees and raising concerns that model results may not be generalizable to other regions and taxa. To assess whether the geographic and taxonomic biases of data could undermine effectiveness of models for conservation policy, we have collated from the published literature a global dataset of bee diversity at sites facing land-use change and intensification, and assess whether bee responses to these pressures vary across 11 regions (Western, Northern, Eastern and Southern Europe; North, Central and South America; Australia and New Zealand; South East Asia; Middle and Southern Africa) and between bumblebees and other bees. Our analyses highlight strong regionally-based responses of total abundance, species richness and Simpson's diversity to land use, caused by variation in the sensitivity of species and potentially in the nature of threats. These results suggest that global extrapolation of models based on geographically and taxonomically restricted data may underestimate the true uncertainty, increasing the risk of ecological surprises

Ozone impedes the ability of a herbivore to find its host

Plant-emitted hydrocarbons mediate several key interactions between plants and insects. They enhance the ability of pollinators and herbivores to locate suitable host plants, and parasitoids to locate herbivores. While plant volatiles provide strong chemical signals, these signals are potentially degraded by exposure to pollutants such as ozone, which has increased in the troposphere and is projected to continue to increase over the coming decades. Despite the potential broad ecological significance of reduced plant signaling effectiveness, few studies have examined behavioral responses of insects to their hosts in polluted environments. Here, we use a laboratory study to test the effect of ozone concentration gradients on the ability of the striped cucumber beetle ( Acalymma vittatum ) to locate flowers of its host plant, Cucurbita foetidissima . Y-tube experiments showed that ozone mixing ratios below 80 parts per billion (ppb) resulted in beetles moving toward their host plant, but levels above 80 ppb resulted in beetles moving randomly with respect to host location. There was no evidence that beetles avoided polluted air directly. The results show that ozone pollution has great potential to perniciously alter key interactions between plants and animals

The effect of inbreeding on the total number of bee visits to octets while controlling for mean floral display size and mean corolla width for the duration of Experiment 1.

<p>Means represent least squares means from repeated measures ANCOVAs using SAS proc mixed after the effect of display size and corolla width had been removed. After statistically controlling for these two important visual cues, bumble bees still discriminate against inbred plants. Means with different letters are significantly different from one another using Tukey-Kramer multiple comparison test. Error bars indicate upper 95% confidence limits.</p

The effect of inbreeding on A) bee visitation to octets and B) probes into flowers for Experiment 1.

<p>Means represent least squares means from repeated measures ANOVAs using SAS proc mixed. Inbreeding reduced visitation and probing by bumble bees. Means with different letters are significantly different from one another using Tukey-Kramer multiple comparison test. Error bars indicate upper 95% confidence limits.</p