Dormancy type, seed traits, and species identity shape seed-associated fungal community composition in tropical...

Seed germination is regulated in many plants by seed dormancy, while postdispersal survival is often determined by soilborne fungi that infect seeds. In tropical forests, seeds in each of three dormancy types (physical, physiologically dormant, or quiescent) often share similar physical and chemical traits. We hypothesized that variation in seed traits aligned with seed dormancy should shape seed-associated fungal communities, linking dormancy to seed survival. Seeds of 18 pioneer tree species were buried in each of five common garden plots in a lowland tropical forest in Panama for up to 36 months. Seeds were screened for viability and fungal infection at intervals throughout the experiment. Plant species with different dormancy types harbored distinct fungal communities. Dormancy type explained 6.5% of variation in fungal community composition after accounting for the far stronger signature of plant species identity (34%). Within dormancy types, differences in seed traits among species explained 49-56% of the variation in fungal communities, suggesting that seed traits drive niche partitioning beyond what is imposed by dormancy type alone. This study shows that variation in seed traits within a dormancy type filters seed-associated fungal communities, which likely shapes the demography of tropical forest trees by influencing seed survival and germination.