Endophytic fungal diversity in whitebark pine: links between species assemblage, biogeography, and blister rust occurrence.

Whitebark pine is a threatened, keystone and foundational species in the northern Rocky Mountains that occurs in a narrow elevational zone and has experienced 40-90% population declines. These declines are due to an invasive fungal disease (white pine blister rust), mountain pine beetle, shifting fire regimes, and climate change. In this study I examined the foliar endophytic fungal communities of whitebark pine across three environmental gradients: mountain range isolation, disease stage, and elevational driven ecotype. Additionally, I examined the host specificity of these communities to another co-dominant subalpine conifer. Our results show that community composition similarity (beta diversity) was significantly driven by study site, disease stage, and ecotype. I found that species richness was greatest at the lowest elevations sampled in this study and that community composition varied significantly between the lowest elevation sites and the highest elevation sites. Results of the study suggest that these communities are highly host specific, and that the loss of whitebark pine will likely lead to the loss of its foliar fungal symbionts. Additionally, species' occurrence patterns and diversity trends of these communities suggest that elevational driven ecotype is a greater driver of community assemblage than mountain range isolation or disease infection state