A spatially explicit model of pollinator-plant-pathogen interactions

Flowers have long been suggested to be infection hotspots for pollinator diseases, as, during their brief lifespan, they are visited and handled by many individuals from a diverse range of species. Evidence that floral hotspots are an important point of contagion is building, but few models currently allow us to characterise these novel plant-pathogen-pollinator systems where horizontal infections occur from concentrated, short-lived sites of contagion. Infection success is going to depend heavily upon the behaviour of individual pollinators, alongside the structure of the floral landscape that they are foraging within. Here, we describe an individual-based model that considers the impact of environmental heterogeneity and individual differences in movement on the spread of a disease that is spread via floral hotspots, considering a centrally nesting social pollinator (such as a social bee). The biggest effects we saw were associated with the likelihoods of leaving and staying in the nest and the distances travelled by the pollinators, and so it is likely that social pollinators, most of which are constrained to return to a central nest, could be strongly impacted by the schedules they use for allocating foraging behaviour. We also considered the impact of the pollinators being able to deposit and detect temporary scent-marks, which could inform an uninfected pollinator of a potentially infected site. Scent marks have a negative impact on pathogen transmission, and their effect may be dependent on both the longevity of the scent mark, the turnover of flowers in the environment, and the factors affecting pathogen viability and infectivity. Overall, although the structure of the landscape may have limited impact on pathogen spread, the behaviour of the pollinators is important, and needs further consideration within models of this pathogen system.