LAUSR

Abstract Despite their importance in structuring plant communities, the identities and spatial distributions of the pathogens impacting wild plant communities are largely unknown. To advance our knowledge of plant-pathogen interactions in tropical forests, I identified likely fungal pathogens from forest sites across a rainfall gradient in Panama and compared the communities of fungi inhabiting a wetter, Atlantic and a drier, Pacific forest (∼45 km apart). Seedlings with symptoms of pathogen attack were collected and fungi were isolated from the symptomatic tissue. Based on internal transcribed spacer region sequences, I assigned the fungal isolates to operational taxonomic units (OTUs) and estimated their taxonomic placements. I observed 28 OTUs (defined by 95% sequence similarity); primarily, the genera Mycoleptodiscus, Glomerella, Bionectria, Diaporthe, and Calonectria. The wetter, Atlantic and drier, Pacific forest sites shared 29% of observed and 56% of non-singleton fungal OTUs, suggesting that, in these forests, the common fungal pathogens of seedlings are relatively widespread, habitat generalists.