First field-based estimates of bumblebee diapause survival rates showcase high survivorship in the wild

Bumblebee (Bombus spp.) queens overwintered in artificial settings tend to have low survival rates, raising concerns that diapause may be a particularly sensitive life cycle stage for this ecologically and economically valuable group of pollinators. However, it remains unclear whether lab-based estimates of diapause survival are comparable to survival rates of natural populations. In this study, we monitored the survival of Bombus impatiens queens overwintering in the field in Ipswich, MA, and conducted a meta-analysis of studies that estimate queen diapause survival in the lab to compare our field-based estimates of survival to those of lab-based studies. We found that queen B. impatiens had relatively high rates of overwintering survival after about six months (> 60%), especially when compared to estimates of six-month survival from lab studies (< 10%). We also observed a trend that broadly corroborates many lab studies of bumblebees, in that overwinter survival of queens was related to colony origin. In addition to providing the first estimate of diapause survival for bumblebee queens in nature, our study emphasizes the need to verify patterns observed in the lab to field-based studies.

Although protecting target species during sensitive life cycle stages is a fundamental goal of conservation ecology, it is first necessary to identify at what stages of the life cycle populations are most vulnerable. Our results suggest that, at least in some study systems, diapause survival of queen bumblebees in the field may be higher than suggested by lab studies.

The online version contains supplementary material available at 10.1007/s10841-023-00478-8.