The earlier the better? Nesting timing and reproductive success in subalpine cavity-nesting bees

1. Reproductive timing can affect an organism’s production of offspring and its offspring’s success, both of which contribute to its overall fitness. In seasonal environments, the timing of reproductive activity may be restricted to short periods of the year owing to numerous potential selective pressures such as variation in daylength, weather, food availability, predation, or competition.

2. We documented the relationships between reproductive timing and individual reproductive success (total reproductive output and offspring success) in subalpine populations of five cavity-nesting solitary bee species. We also examined the relationships between bee reproductive success and environmental variables that are likely ultimate drivers of bee phenology in subalpine environments (i.e., seasonality of floral resource abundance and temperature).

3. Over six years, we recorded solitary bee nesting timing, egg production, and offspring success using artificial nesting structures (“trap-nes...