Phyllosphere bacterial communities in milkweeds: composition diverge as the season progresses, and links to cardenolides and arthropods depend on host identity
Leaf bacterial communities shape plant defense and interactions with herbivores, yet how host filtering and stochastic processes assemble them remains unclear. We predicted that host identity, chemistry, and arthropods structure them, and that stochastic and deterministic contributions shift seasonally. Across one growing season we sampled leaf bacteria monthly and arthropods weekly on four…
The phyllosphere bacterial communities of milkweed plants undergo shifts in composition throughout the growing season, influenced by host identity, chemistry, and arthropod interactions, according to a study tracking four Asclepias species. Researchers collected leaf bacteria samples monthly and arthropod samples weekly, sequencing 16S rRNA genes to analyze turnover and contributing factors.
Host identity significantly impacted bacterial richness and composition, with A. tuberosa hosting the most diverse communities. As the season progressed, community similarity among plants increased due to homogenizing dispersal, but by mid-season, no single process dominated turnover, and by late season, dispersal limitation took over.
Initially, selection was episodic and not sustained, while arthropod associations were host-specific, particularly unfavorable on A. syriaca. The study revealed that phyllosphere assembly transitions from convergence to divergence within one season, with young leaves sourcing microbes from a shared pool and older plants' communities drifting apart.
Late herbivores encountered plant-specific microbial environments, suggesting that microbial mediation of herbivory is host-specific and seasonally contingent.
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