<b>Site-specific differences in the bilberry (</b> <i> <b>Vaccinium myrtillus</b> </i> <b>) phyllosphere microbiome across temperate and arctic locations</b>

The phyllosphere microbiome plays a crucial role in plant adaptation to environmental conditions, yet little is known about its variation across climate extremes. We profiled leaf-associated (epiphytic + endophytic) microbial communities of bilberry (Vaccinium myrtillus) from temperate (Jena, Germany) and Arctic (Tromsø, Norway) sites using shotgun metagenomics. Taxonomic and functional profiles revealed region-associated differences alongside a shared core microbiome. While alpha diversity did not differ significantly, ordination suggested a trend toward trend-associated compositional differences. Trait summaries indicated that taxa enriched in Tromsø commonly carried features linked to cold and oxidative-stress resilience, whereas Jena-enriched taxa tended toward faster growth and facultative metabolism. Despite the limited sample size and one site per region, these patterns are consistent with environment-associated filtering of phyllosphere communities. Our findings provide a descriptive baseline for targeted, hypothesis-driven tests of microbial functions relevant to plant resilience under shifting climates and suggest that V. myrtillus has potential as a model for studying climate-microbiome interactions in perennial plants.