Search for: All records

Infectious disease is a major driver of biodiversity loss, but how disease threatens pollinator communities remains poorly understood. Here, we review the plant–pollinator–pathogen literature to identify mechanisms by which plant and pollinator traits and community composition influence pathogen transmission and assess consequences of transmission on plant and pollinator fitness. We find that plant and pollinator traits that increase floral contact can amplify transmission, but community-level factors such as plant and pollinator abundance are often correlated and can counteract one another. Although disease reduces pollinator fitness in some species, little research has assessed cascading effects on pollination, and taxonomic representation outside of honey bees and bumble bees remains poor. Major open challenges include (a) disentangling correlations between plant and pollinator abundance to understand how community composition impacts pathogen transmission and (b) distinguishing when pathogen transmission results in disease. Addressing these issues, as well as expanding taxonomic representation of pollinators, will deepen our understanding of how pathogens impact diverse pollinator communities. 

Summary Epiphytic microbes frequently affect plant phenotype and fitness, but their effects depend on microbe abundance and community composition. Filtering by plant traits and deterministic dispersal‐mediated processes can affect microbiome assembly, yet their relative contribution to predictable variation in microbiome is poorly understood.We compared the effects of host‐plant filtering and dispersal on nectar microbiome presence, abundance, and composition. We inoculated representative bacteria and yeast into 30 plants across four phenotypically distinct cultivars ofEpilobium canum. We compared the growth of inoculated communities to openly visited flowers from a subset of the same plants.There was clear evidence of host selection when we inoculated flowers with synthetic communities. However, plants with the highest microbial densities when inoculated did not have the highest microbial densities when openly visited. Instead, plants predictably varied in the presence of bacteria, which was correlated with pollen receipt and floral traits, suggesting a role for deterministic dispersal.These findings suggest that host filtering could drive plant microbiome assembly in tissues where species pools are large and dispersal is high. However, deterministic differences in microbial dispersal to hosts may be equally or more important when microbes rely on an animal vector, dispersal is low, or arrival order is important. 

ABSTRACT Variation in dispersal ability among taxa affects community assembly and biodiversity maintenance within metacommunities. Although fungi and bacteria frequently coexist, their relative dispersal abilities are poorly understood. Nectar-inhabiting microbial communities affect plant reproduction and pollinator behavior, and are excellent models for studying dispersal of bacteria and fungi in a metacommunity framework. Here, we assay dispersal ability of common nectar bacteria and fungi in an insect-based dispersal experiment. We then compare these results with the incidence and abundance of culturable flower-inhabiting bacteria and fungi within naturally occurring flowers across two coflowering communities in California across two flowering seasons. Our microbial dispersal experiment demonstrates that bacteria disperse via thrips among artificial habitat patches more readily than fungi. In the field, incidence and abundance of culturable bacteria and fungi were positively correlated, but bacteria were much more widespread. These patterns suggest shared dispersal routes or habitat requirements among culturable bacteria and fungi, but differences in dispersal or colonization frequency by thrips, common flower visitors. The finding that culturable bacteria are more common among nectar sampled here, in part due to superior thrips-mediated dispersal, may have relevance for microbial life history, community assembly of microbes, and plant–pollinator interactions.