Abstract: Mycorrhizal fungi represent a widespread group of fungi in nature that form symbiotic associations with most terrestrial plants, playing a crucial role in plant physiological processes and terrestrial ecosystem functioning. In these symbiotic relationships, mycorrhizal fungi receive photosynthesis-derived carbon from their host plants and, in turn, facilitate the host plants with regard to nutrient acquisition and stress tolerance. Recently, the rapid development of molecular biology and bioinformatics has significantly advanced our understanding of mycorrhizal physiology and ecology. To summarise the important progress in these fields, we reviewed the differences in the evolutionary history of arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) fungi, as well as their impacts on the physiological and ecological functions of host plants. We further discussed how these differences affect the nutrient cycling of global terrestrial ecosystems and the structure and function of plant communities. We showed that the origin and evolution of AM and EcM fungi is a process of long-term mutual adaptation and selection with terrestrial plants. During the evolution, mycorrhizal fungi have gradually refined their plant-dependent nutrient acquisition mechanisms, while plants have developed diverse growth strategies to optimize symbiosis with mycorrhizal fungi. In these mutually beneficial interactions, mycorrhizal fungi not only enhance the nutrient uptake and utilization in host plants and improve their tolerance to biotic and abiotic stresses, but also participate in global biogeochemical cycles. Thus, mycorrhizal fungi play a vital role in maintaining the balance and stability of biodiversity and terrestrial ecosystems. Finally, we proposed future research directions, including the response of mycorrhizal fungi to global change, their roles in multi-trophic associations and urban ecosystems, as well as their applications in production practices and diversity conservation, aiming to provide novel insights and approaches to address various ecological and social challenges.

Key words: Arbuscular mycorrhizal fungi, ectomycorrhizal fungi, morphological structure, biodiversity, ecosystem functioning, terrestrial ecosystem