Maintenance of host specialisation gradients in ectomycorrhizal symbionts

• Published in: The New phytologist Vol. 242; no. 4; pp. 1426 - 1435
• Main Authors: Voller, Fay, Ardanuy, Agnès, Taylor, Andy F. S., Johnson, David
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.05.2024; Wiley
• Subjects: Arbuscular mycorrhizas; Colonization; Ectomycorrhizas; Fungi; Genetics; heterorhizic roots; Host plants; host specialist; Isotopes; Life Sciences; Mycorrhizae - physiology; partner choice; Plant Roots - microbiology; Plant Roots - physiology; resource exchange; Specialization; Speciation; Symbionts; Symbiosis; Symbiosis - physiology; Tracers; resource exchange; host specialist; partner choice; heterorhizic roots; speciation; heterorhizic rootshost; specialist
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.19395

Summary Many fungi that form ectomycorrhizas exhibit a degree of host specialisation, and individual trees are frequently colonised by communities of mycorrhizal fungi comprising species that fall on a gradient of specialisation along genetic, functional and taxonomic axes of variation. By contrast, arbuscular mycorrhizal fungi exhibit little specialisation. Here, we propose that host tree root morphology is a key factor that gives host plants fine‐scale control over colonisation and therefore opportunities for driving specialisation and speciation of ectomycorrhizal fungi. A gradient in host specialisation is likely driven by four proximate mechanistic ‘filters’ comprising partner availability, signalling recognition, competition for colonisation, and symbiotic function (trade, rewards and sanctions), and the spatially restricted colonisation seen in heterorhizic roots enables these mechanisms, especially symbiotic function, to be more effective in driving the evolution of specialisation. We encourage manipulation experiments that integrate molecular genetics and isotope tracers to test these mechanisms, alongside mathematical simulations of eco‐evolutionary dynamics in mycorrhizal symbioses.