Pervasive Effects of Wildfire on Foliar Endophyte Communities in Montane Forest Trees

Plants in all terrestrial ecosystems form symbioses with endophytic fungi that inhabit their healthy tissues. How these foliar endophytes respond to wildfires has not been studied previously, but is important given the increasing frequency and intensity of severe wildfires in many ecosystems, and because endophytes can influence plant growth and responses to stress. The goal of this study was to examine effects of severe wildfires on endophyte communities in forest trees, with a focus on traditionally fire-dominated, montane ecosystems in the southwestern USA. We evaluated the abundance, diversity, and composition of endophytes in foliage of Juniperus deppeana (Cupressaceae) and Quercus spp. (Fagaceae) collected contemporaneously from areas affected by recent wildfire and paired areas not affected by recent fire. Study sites spanned four mountain ranges in central and southern Arizona. Our results revealed significant effects of fires on endophyte communities, including decreases in isolation frequency, increases in diversity, and shifts in community structure and taxonomic composition among endophytes of trees affected by recent fires. Responses to fire were similar in endophytes of each host in these fire-dominated ecosystems and reflect regional fire-return intervals, with endophytes after fire representing subsets of the regional mycoflora. Together, these findings contribute to an emerging perspective on the responses of diverse communities to severe fire, and highlight the importance of considering fire history when estimating endophyte diversity and community structure for focal biomes.