Plant–fungal interactions in arid and semi-arid ecosystems: Large-scale impacts from microscale processes

The roles of microbes in shaping plant communities have historically been underestimated. Recent improvements in our abilities to detect, identify, and monitor microbial inhabitants of plant tissues are increasing our appreciation of the complex microbial dynamics in arid and semi-arid ecosystems. Microbial endophytes can modify plants at genetic, physiologic, and ecologic levels. These modifications induce profound changes in how plants respond to their environments, with potential consequences in terms of spatial variation in vegetation dynamics. Microscale examination of Bouteloua eriopoda (black grama) and Atriplex canescens (fourwing saltbush) collected in the northern Chihuahuan Desert revealed diverse fungal communities associated with individual plants at the cellular and subcellular levels. To explore thresholds of plant fitness defined by microbial communities, endophytes from B. eriopoda were transferred to Sporobolus cryptandrus (sand dropseed), and endophytes from S. cryptandrus and A. canescens were transferred to B. eriopoda. Dramatic, whole-plant differences in morphology and biomass between treated and untreated plants were observed. Treated plants were generally larger, with greater reproductive potential than untreated controls. We hypothesize that these transformed plants will continue to out-perform their native counterparts, propagating changes from the plant–microbe interface to ecologically significant scales.