Honeybees are an economically important pollinator whose populations face numerous threats, including parasites, disease, and pesticide exposure. However, because they are social, it can be difficult to predict how factors affecting the health or longevity of individuals will scale up to effects on the entire colony. Honeybees also have extraordinary phenotypic plasticity in their aging rate, with seasonal variation in both senescence and extrinsic mortality resulting in up to tenfold differences in worker life expectancy. Borrowing methods from population modelling, we develop a matrix model of colony demographics to ask how worker age-dependent and age-independent mortality affect colony fitness and how these effects differ by seasonal conditions.
Results/Conclusions
We find that there are seasonal differences in honeybee colony sensitivity to both senescent and extrinsic worker mortality. Surprisingly, we find that colonies are more sensitive to both sources of mortality under conditions of low resource availability. This suggests that colonies will be more sensitive to threats of all types during those conditions. Furthermore, this difference in colony sensitivity to worker mortality suggests that selection for low worker senescence should be higher during periods of resource dearth, partly explaining the observed pattern of seasonal differences in worker aging.