Disease and diet: what predicts colony longevity in an invasive Vespula population with occasional perenniality?
Kevin J. Loope, Kevin J. Loope , Erin E. Wilson Rankin
Department of Entomology, University of California, Riverside, USA; Department of Entomology, University of California, Riverside, USA ; Department of Entomology, University of California, Riverside, USA
In geographic regions with warm winters, invasive yellowjacket wasp colonies (genus Vespula) often exhibit polygyny (multiple queens) and persist for multiple years, though these phenomena are rare in the native range where colonies have an annual cycle. Although 5-20% of colonies survive into a second season in our study population of invasive Vespula pensylvanica in Hawaii Volcanoes National Park, and these perennial colonies are ecologically much more damaging than their annual counterparts, we know little about what explains variation in colony persistence through the winter. To address this gap, we tracked the longevity of wild colonies through the winters of 2016-17 (n=76) and 2017-18 (n=42). We found that colony-level Moku virus load, assessed in October when annual colonies are reproducing, negatively influenced colony longevity. However, neither proximity to feral honeybee hives, nor diet supplementation with dead honeybees and honey, influenced colony longevity in these years. Sampling large numbers of wild colonies allowed us to detect spatial patterns in disease loads across colonies, with positive spatial correlation of pathogen load for Moku virus, Arsenophonus bacteria, and trypanosomes. These patterns raise new questions about how the spatial arrangement of colonies and landscape features may influence pathogen transmission and colony longevity.