EFFECTS OF COASTAL PROCESSES ON ENDOPHYTIC FUNGAL COMMUNITIES

Abstract

Coastal ecosystems are important for many biosphere processes relevant to human sustainability. These ecosystems support and depend on plants and algae that in turn interact closely with fungal endophytes. Endophytes often are important in enhancing host health and resilience to stress. How these endophytes respond to environmental stressors is not well understood. By studying communities of endophytes across environmental gradients we can gain insight into their ecological distributions and sensitivity to particular environmental factors. In this study I examined endophyte communities associated with a gradient from coastal conditions in a Pacific fog-desert environment to inland mountains in the semiarid area near Tucson, Arizona. Specifically, I collected marine macroalgae and plants at multiple sites in Cabrillo National Monument (Pacific coast) as well as congeneric plants that occur at the Santa Catalina Mountains (Mt. Lemmon, in Arizona). I anticipated that communities of endophytes would differ in the coastal vs. inland area. To gain insight into a factor potentially influencing such a difference, I conducted a salinity (NaCl) tolerance bioassay on a species that was found in both the tide pools at Cabrillo and at Mt. Lemmon. I found that the community composition of endophytes between Cabrillo and Mt. Lemmon differ markedly. Closely related plants host different species in each site, suggesting that there are strong environmental drivers of local endophyte composition. Aligned with this interpretation, I found that endophytes from macroalgae at Cabrillo had a higher salt tolerance than their counterparts from Mt. Lemmon, and that they likely need NaCl in their medium to grow optimally. Overall my results are consistent with a coastal ecosystem feature (salinity) influencing the composition of endophyte communities, suggesting a powerful impact of a coastal process on symbionts and highlighting how endophyte communities vary at a regional scale. Based on my study, I suggest the development of a less harsh protocol for endophyte isolation from marine macroalgae is warranted, and that an NGS-based study of coastal fog desert endophytes should be employed to look for unculturable fungi.