Phenology of reproduction in bumble bee colonies

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In recent years, many plant and animal populations have changed the timing of life cycle events. Early season events, like flowering of fruit trees and emergence of butterflies, are occurring earlier than they did in the past, and late season events, like fall migration of birds and changing leaf colors, are happening later than they did in the past. These changes in phenology (the timing of life cycle events) are considered one of the most conspicuous effects of climate change on plant and animal populations. This research project will investigate the ways in which the phenology of bumble bee colonies is changing through time. Although we tend to treat bumble bees as a single species, there are actually more than 40 species of bumble bees in the United States, and these species might respond in different ways to climate change. Understanding these changes is especially important because bumble bees are one of the most important groups of pollinators of wild and crop plants. If bumble bee life cycles change, or if bumble bee species decline, there are likely to be negative consequences for food security, as well as cascading declines in wild plant communities. The researchers will organize workshops for scientists and conservation specialists and share the methods they will develop for studying bumble bees. The project will engage the general public with activities for pollinator gardening and pollinator conservation.This project will compare the phenology of two bumble bee species. Bombus impatiens, the common eastern bumble bee, has a long-life cycle that lasts from early spring to late fall. Bombus griseocollis, the brown-belted bumble bee, has a short life cycle ending in mid-summer. In the 1970’s and 1980’s, theoretical ecologists developed models about why bumble bees switch to reproduction when they do. This research will test these models by monitoring the phenology of both species in relation to among-year variation in temperature and the availability and timing of flowers that bumble bees can forage on (which is likely to depend on temperature and drought). The researchers will also use citizen scientist data to evaluate latitudinal and temporal changes in phenology of different bumble bee species in geographic regions and time periods with different growing season lengths. The project will test predictions of the classical theories of bumble bee colony reproduction, including the prediction that species with longer life cycles during the year are more sensitive to variation among years. This project will provide new knowledge about nesting and hibernation habitat needs of bumble bees as an important contribution to conservation efforts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.