title: From mycoheterotrophy to mutualism: mycorrhizal specificity and functioning in Ophioglossum vulgatum sporophytes.
abstract: Mycorrhizal functioning in the fern Ophioglossum is complex and poorly understood. It is unknown whether mature O. vulgatum sporophytes form mutualistic associations with fungi of the Glomeromycota and with what specificity. Are green sporophytes able to 'repay' fungal carbon (C) invested in them by mycorrhizal partners during the initially heterotrophic gametophyte and early sporophyte stages of the lifecycle? We identified fungal partners of O. vulgatum sporophytes using molecular techniques and supplied them with (33) P-orthophosphate and O. vulgatum sporophytes with (14) CO2 . We traced the movement of fungal-acquired nutrients and plant-fixed C between symbionts and analysed natural abundance (13) C and (15) N isotope signatures to assess nutritional interactions. We found fungal specificity of O. vulgatum sporophytes towards a mycorrhizal fungus closely related to Glomus macrocarpum. Our radioisotope tracers revealed reciprocal C-for-phosphorus exchange between fern sporophytes and fungal partners, despite competition from surrounding vegetation. Monocultures of O. vulgatum were enriched in (13) C and (15) N, providing inconclusive evidence of mycoheterotrophy when experiencing competition from the surrounding plant community. We show mutualistic and specific symbiosis between a eusporangiate fern and fungi of the Glomeromycota. Our findings suggest a 'take now, pay later' strategy of mycorrhizal functioning through the lifecycle O. vulgatum, from mycoheterotrophic gametophyte to mutualistic aboveground sporophyte.
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: Katie J
authors.initials: KJ
authors.lastname: Field
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Leake
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Tille
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: Kate E
authors.initials: KE
authors.lastname: Allinson
authors.affiliation: Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK.|Jodrell Laboratory, Royal Botanic Gardens, Kew, TW9 3DS, UK.|Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK.
authors.forename: William R
authors.initials: WR
authors.lastname: Rimington
authors.affiliation: Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK.|Jodrell Laboratory, Royal Botanic Gardens, Kew, TW9 3DS, UK.
authors.forename: Martin I
authors.initials: MI
authors.lastname: Bidartondo
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beerling
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: Duncan D
authors.initials: DD
authors.lastname: Cameron
mesh_terms: D000704:Analysis of Variance; D005075:Biological Evolution; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D015169:Colony Count, Microbial; D029624:Ferns / Q000382:microbiology*; D055137:Glomeromycota / Q000254:growth & development / Q000502:physiology*; D052836:Heterotrophic Processes / Q000502:physiology*; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000254:growth & development / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D013045:Species Specificity; D013559:Symbiosis / Q000502:physiology*
chemical_list: D012987:Soil; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen
keywords: Ophioglossaceae; Ophioglossum vulgatum; competition; ferns; mycoheterotrophy; mycorrhiza; specificity; symbiosis