Meeting Abstract
The alfalfa leafcutting bee, Megachile rotundata, is an extensively managed solitary bee that may experience low temperature stress during metamorphosis. After diapause, pupae can be exposed to cold stress through spring cold snaps and agricultural practices that postpone development until crop conditions are favorable. Cold stress has been found to cause abnormalities in adult bees. However, the effects of low temperature stress on their reproductive fitness is unknown. The purpose of this study was to test the hypothesis that cold stress reduces fitness. Pupae were exposed to either constant or fluctuating cold stress for one week during metamorphosis, released into an alfalfa field after adult emergence, and compared to bees that were not interrupted. Twenty females and 10 males were released in 9 field tents (6.1m x 6.1m x 2.4m) placed in an alfalfa field and monitored for 3 weeks. Fitness and offspring characteristics were measured by the number of offspring, sex ratio, and diapause incidence. Bees exposed to constant cold stress had fewer offspring compared to controls or bees exposed to fluctuating temperatures. While the fluctuating treatment did not cause a reduction in fitness, offspring were more likely to enter diapause, suggesting mothers interpreted environmental conditions differently. This study is the first to show how field performance, fitness, and offspring characteristics, are affected by a stressor experienced before adult emergence in M. rotundata.
