Fungal communities associated with roots of two closely related Juglandaceae species with a disjunct distribution in the tropics

Diversity and distribution of tropical ectomycorrhizal fungi

The tropics were long considered to have few ectomycorrhizal fungi, presumably due to a paucity of ectomycorrhizal host plants relative to higher-latitude ecosystems. However, an increase in research in tropical regions over the past 30 years has greatly expanded knowledge about the occurrence of tropical ectomycorrhizal fungi. To assess their broad biogeographic and diversity patterns, we conducted a comprehensive review and quantitative data analysis of 49 studies with 80 individual data sets along with additional data from GlobalFungi to elucidate tropical diversity patterns and biogeography of ectomycorrhizal fungi across the four main tropical regions: the Afrotropics, the Neotropics, Southeast Asia, and Oceania. Generalized linear models were used to explore biotic and abiotic influences on the relative abundance of the 10 most frequently occurring lineages. We also reviewed the available literature and synthesized current knowledge about responses of fungi to anthropogenic disturbances, and their conservation status and threats. We found that /russula-lactarius and /tomentella-thelephora were the most abundant lineages in the Afrotropics, the Neotropics, and Southeast Asia, whereas /cortinarius was the most abundant lineage in Oceania, and that /russula-lactarius, /inocybe, and /tomentella-thelephora were the most species-rich lineages across all of the tropical regions. Based on these analyses, we highlight knowledge gaps for each tropical region. Increased sampling of tropical regions, collaborative efforts, and use of molecular methodologies are needed for a more comprehensive view of the ecology and diversity of tropical ectomycorrhizal fungi.

Ectomycorrhizal Assemblages of Invasive Quercus rubra L. and Non-Invasive Carya Nutt. Trees under Common Garden Conditions in Europe

Invasive tree species change biodiversity, nutrient cycles, and ecosystem services, and can turn native ecosystems into novel ecosystems determined by invaders. In the acclimatization and invasion of alien tree species, the crucial role is played by ectomycorrhizal (ECM) fungi. We tested ECM fungi associated with Quercus rubra and Carya trees that are alien to Europe. Quercus rubra is among the most invasive tree species in Europe, and the Carya species are not considered invasive. Both form ectomycorrhizal symbiosis, and in their native range in North America, coexist in oak-hickory forests. Six study stands were located in Kórnik Arboretum: three for Q. rubra and three for Carya trees. Ectomycorrhizal fungi were assessed by molecular identification of ECM roots. We identified 73 ECM fungal taxa of 23 ECM phylogenetic lineages. All identified ECM fungi were native to Europe. Similar richness but different composition of ECM taxa were found on Q. rubra and Carya roots. Phylogenetic lineages /tomentella-thelephora, /russula-lactarius, and /genea-humaria were most abundant on both Carya and Q. rubra roots. Lineages /tuber-helvella and /entoloma were abundant only on Carya, and lineages /pisolithus-scleroderma and /cortinarius were abundant only on Q. rubra roots. Analysis of similarities revealed a significant difference in ectomycorrhizal assemblages between invasive Q. rubra and non-invasive Carya. Highlights: (1) under common garden conditions, ECM taxa richness was similar on Q. rubra and Carya roots; (2) ECM taxa composition differed between invasive Q. rubra and non-invasive Carya; (3) high abundance of long-distance exploration type (lineages from Boletales) was on Q. rubra; and (4) high abundance of short-distance exploration type (e.g., /tuber-helvella) was on Carya.