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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.
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This content will become publicly available on May 1, 2026
Nectar peroxide: assessing variation among plant species, microbial tolerance, and effects on microbial community assembly
Nectar contains antimicrobial constituents including hydrogen peroxide, yet it is unclear how widespread nectar hydrogen peroxide might be among plant species or how effective it is against common nectar microbes.Here, we surveyed 45 flowering plant species across 23 families and reviewed the literature to assess the field‐realistic range of nectar hydrogen peroxide (Aim 1). We experimentally explored whether plant defense hormones increase nectar hydrogen peroxide (Aim 2). Further, we tested the hypotheses that variation in microbial tolerance to peroxide is predicted by the microbe isolation environment (Aim 3); increasing hydrogen peroxide in flowers alters microbial abundance and community assembly (Aim 4), and that the microbial community context affects microbial tolerance to peroxide (Aim 5).Peroxide in sampled plants ranged from undetectable toc3000 μM, with 50% of species containing less than 100 μM. Plant defensive hormones did not affect hydrogen peroxide in floral nectar, but enzymatically upregulated hydrogen peroxide significantly reduced microbial growth.Together, our results suggest that nectar peroxide is a common but not pervasive antimicrobial defense among nectar‐producing plants. Microbes vary in tolerance and detoxification ability, and co‐growth can facilitate the survival and growth of less tolerant species, suggesting a key role for community dynamics in the microbial colonization of nectar.
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- Award ID(s):
- 1846266
- PAR ID:
- 10616371
- Publisher / Repository:
- New Phytologist
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 246
- Issue:
- 3
- ISSN:
- 0028-646X
- Page Range / eLocation ID:
- 1361 to 1376
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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