Insight into recent studies on the diversity of arbuscular mycorrhizal fungi in shaping plant community assembly and maintaining rare species

Arbuscular mycorrhiza (AM) is one of the oldest symbionts between plants and soil microorganisms, and about 80% terrestrial plant species can associate with AM fungi on earth.Because of the stable climate and poor soil phosphorus content in tropical and subtropical forests, this mutualistic symbiosis is much more common there.Previous studies have extensively investigated the diversity of AM fungi in tropical and subtropical forests, and have shown that AM fungi can promote plant recruitment and growth.However, this positive effect of AM fungi on plants (i.e., the positive plant-soil feedback) can weaken the contribution of the negative plant-soil feedback (caused by soil-borne pathogens) to maintaining tree species diversity, which appears to contradict with the surprisingly high tree diversity and high proportion of rare tree species in tropical and subtropical forests.Recently, a mounting number of empirical studies have found that the diversity of AM fungi varies significantly in different habitats and AM colonization depends on the identity of host species, thereby affecting the fitness of plants and further shaping the plant community structure.Through synthesizing the current research about the diversity of AM fungi in promoting plant coexistence and maintaining community diversity, we expect to put forward a promising study direction for testing the "rare species advantage" hypothesis, therefore improving the conservation of rare plant species.