From agroecosystems to natural ecosystems: Assessing wild bee population status and health in a changing world

Both natural ecosystems and fruit and vegetable production in agriculture are dependent on the pollination services provided by wild, native bees. Abiotic and biotic stressors, including climate change, land-use change, and infectious disease, are expected to affect bee population turnover and reduce their densities. However, most research assessing bee population status or health in response to stress is conducted using managed species, and the extent to which these stressors impact wild populations is largely unknown. Thus, identifying alternative model species that represent more native bees’ life histories, in addition to implementing diverse tools and techniques for evaluating populations and their health, is critical for predicting native bee response to stress. First, we discuss using Xenoglossa pruinosa as a model species to assess wild, solitary bee health in highly-managed agricultural contexts. We evaluated X. pruinosa responses to temperature and parasite pressure in squash agroecosystems, and reveal that heat and parasite intensity reduce variation in thermal tolerance. Second, we discuss status assessments for wild populations in unmanaged natural systems using single nucleotide polymorphism (SNP) data. We evaluated population turnover and densities for three bumble bee species in the Madrean sky islands over 10 years, and found that one species, Bombus centralis, is exhibiting high levels of relatedness over time. Overall, we suggest that a wider breadth of species is used in stress-response studies to increase representation of the diversity of native bee traits. We also advocate for long-term monitoring and the use of genetic tools to evaluate the status of sensitive populations.