Meeting Abstract

P3.35  Friday, Jan. 6  Seasonal variation in body size of native bees: thermal constraint or resource limitation? BELL, C.B.*; DILLON, M.E.; University of Wyoming, Laramie; University of Wyoming, Laramie cbell@uwyo.edu

Body size has profound implications for the physiology and ecology of insect pollinators, and strongly affects their role within pollinator networks. Several considerations suggest that size distributions of insect pollinators may change seasonally, with potential impacts on pollination services. However, with few exceptions, we have little data on seasonal changes in size distributions of pollinator species or communities. We measured body sizes of native bees sampled weekly throughout the growing season at sites in southeastern Wyoming. Given the scaling of metabolic rates and heat loss with body size, larger bees should be able to warm up more quickly and therefore have larger activity windows in the cooler conditions of early spring. Thermoregulatory considerations therefore predict larger bees earlier in the season. Alternatively, body size may be driven by resource partitioning within the nest which depends in part on seasonal availability of floral resources. We found that bees were small in early spring when temperatures were low and flowers were scarce and largest in mid-summer when temperatures increased and flowers were most abundant. These results suggest that floral resources rather than thermal constraints may drive seasonal changes in body size in these communities.