Intraspecific variation in realized dispersal probability and host quality shape nectar microbiomes

Abstract

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 of Epilobium 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.

Nontarget impacts of neonicotinoids on nectar‐inhabiting microbes

“…Experimental flowers were selected and inoculated with a standardised microbe community containing 10 4 cells μL −1 of each of a subset of four species from the plate reader experiment (Table 1) in a 20% v/v glycerol, 20% m/v sucrose stock (4 × 10 4 total cells μL −1 ). Microbes were stored in pure culture aliquots at −80°C that were thawed and mixed the morning of each day of inoculations as in Francis et al (2023). All four microbes in the inoculum were confirmed to be successfully culturable on agar media and from trial flowers prior to experiments.…”

Lettuce seedlings rapidly assemble their microbiome from the environment through deterministic processes

“…Previous studies have focused on testing whether deterministic or stochastic processes dominate the assembly of the plant microbiome; however, results from previous studies have produced contrasting outcomes. There is evidence of deterministic processes driving the assembly of leaf and root microbiomes [9][10][11][12][13][14][15], but also evidence suggesting that stochastic processes are dominant [16][17][18][19][20][21]. Some studies suggest that the assembly of bacterial and fungal communities is often driven by contrasting processes, which may vary according to the plant organ [9,14,22,23].…”