Priority effects of foliar fungal endophytes in leaf litter decomposition

PI: Gerald M. Cobián

Foliar endophytic fungi live inside plant leaves and are invisible to the unaided eye. These fungi can defend against pathogens and help plants retain water in arid environments, but many of their ecological roles remain unclear. We hypothesized that certain endophytes persist in leaves as dormant commensals, becoming active upon senescence to initiate decomposition and influence subsequent fungal community assembly via priority effects. We tested this through a 36-week field experiment using Quercus lobata leaf litter in mesh bags exposed to different fungal treatments. Using high-throughput sequencing, we tracked fungal community shifts and found that while distinct taxa were associated with each treatment, decomposition rates were similar. Site-level effects and stochastic processes played a larger role in shaping community composition than endophyte presence. Our findings suggest that endophytes exert weak priority effects under natural conditions and highlight the complexity of fungal interactions in litter decomposition.