The Increased Environmental Niche of Dual-Mycorrhizal Woody Species

The presence and distribution of mycorrhizal symbionts can influence plant distribution through specific host–mycorrhiza symbiosis interactions. However, generalist hosts also exist, such as dual–mycorrhizal plants that form symbiotic associations with both ectomycorrhizal fungi (EM) and arbuscular mycorrhizal fungi (AM). Little is known about the effect of dual mycorrhization status on the hosts' global distribution and acclimation to specific environments. This study investigates the potential advantage of dual associations of more than 400 woody genera spread at a global scale. We found that dual-host woody species occupy a broader geographical range and environmental niche space compared to those associating exclusively with either AM or EM. We show that the increased geographic range and expanded environmental niche space are independent of the phylogenetic architecture and evolutionary history of the woody genera. Our results highlight the advantage of generalist host–microbe symbioses between woody species and fungi to expand their range, and their potential role in colonising dry climates.