The ecological dynamics and consequences of phytoplasma in a spring ephemeral

Ecologists have long sought to link within-population dynamics to patterns of species occurrence and persistence across the range. Theoretical models suggest pathogens have important implications for plant populations and perhaps even limit plant distributions, though more empirical evidence is needed, especially in wild plant populations. In the field, we characterized the infection dynamics of phytoplasma, a vectored and sterilizing bacterial pathogen, in wild populations of white trillium. We identified the bacterial strain and local vectors. We then leveraged community science data to reveal patterns and potential drivers of phytoplasma occurrence across the range of white trillium. Within populations, we found that phytoplasma infection presence was more likely in low host density plots, where insect vectors occupied a higher proportion of trillium, indicative of an encounter-dilution effect. Leafhoppers in the genus Empoasca are the likely vectors of Candidatus Phytoplasma pruni-related, group 16SrIII infections between trilliums. Phytoplasma was widely distributed across trilliums range, even at range edges, and probability of infection was significantly reduced by hotter summer temperatures and increased by proximity to cropland. Our results suggest vectored pathogens are sensitive to local host population densities and able to persist across both the core and edge of host ranges.