Mycorrhizas shape the evolution of plant adaptation to drought

SummaryPlant adaptation to drought facilitates major ecological transitions, and is likely to play a vital role under looming climate change. Mycorrhizas can influence the physiological capacity of plants to tolerate drought. Here, I show how mycorrhizal strategy and drought adaptation shape one another throughout the course of plant evolution.To characterize the evolutions of both plant characters, I applied a phylogenetic comparative method using data of 1,638 extant species globally distributed.The detected correlated evolution unveiled gains and losses of drought tolerance occurring at faster rates in lineages with an ecto- or ericoid mycorrhizal strategy, which were on average about 15 and 300 times quicker than that in lineages with the arbuscular mycorrhizal and naked root (non-mycorrhiza or facultatively arbuscular mycorrhiza) strategy, respectively. Among mycorrhiza shifts, the arbuscular mycorrhiza losses in drought sensitive lineages were more frequent than any symbiont switching or other mutualism breakdown.My study suggests that mycorrhizas play a key facilitator role in the evolutionary process of plant adaptation to critical changes in water availability across global climates.