A Gravity Model for the Spread of a Pollinator-Borne Plant Pathogen

Abstract

Many pathogens of plants are transmitted by arthropod vectors whose movement between individual hosts is influenced by foraging behavior. Insect foraging has been shown to depend on both the quality of hosts and the distances between hosts. Given the spatial distribution of host plants and individual variation in quality, vector foraging patterns may therefore produce predictable variation in exposure to pathogens. We develop a "gravity" model to describe the spatial spread of a vector-borne plant pathogen from underlying models of insect foraging in response to host quality using the pollinator-borne smut fungus Microbotryum violaceum as a case study. We fit the model to spatially explicit time series of M. violaceum transmission in replicate experimental plots of the white campion Silene latifolia. The gravity model provides a better fit than a mean field model or a model with only distance-dependent transmission. The results highlight the importance of active vector foraging in generating spatial patterns of disease incidence and for pathogen-mediated selection for floral traits.

Identification and cloning of class II and III chitinases from alkaline floral nectar of Rhododendron irroratum, Ericaceae

“…Insects that visit flowers are non-sterile (Evans and Armstrong 2006), therefore as well as pollen, they can also transfer between flowers any microorganisms that they carry (Ferrari et al 2006). Furthermore, flowers can remain open for several days, during which time their metabolically rich nectar would potentially allow microbial growth in close proximity to the plant's reproductive tract.…”