J Syst Evol ›› 2016, Vol. 54 ›› Issue (6): 666-678.DOI: 10.1111/jse.12227

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Pteridophyte fungal associations: Current knowledge and future perspectives

Silvia Pressel1, Martin I. Bidartondo2,3, Katie J. Field4, William R. Rimington1,2,3, and Jeffrey G. Duckett1*   

  1. 1Department of Life Sciences, Natural History Museum, London, SW7 5BD, UK
    2Royal Botanic Gardens, Kew, Richmond, TW9 3DS, UK
    3Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
    4School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
  • Received:2016-07-05 Published:2016-12-15

Abstract: Current understanding of the nature and function of fungal associations in pteridophytes is surprisingly patchy given their key evolutionary position, current research foci on other early-branching plant clades, and major efforts at unravelling mycorrhizal evolution and the mechanisms underlying this key interaction between plants and fungi. Here we provide a critical review of current knowledge of fungal associations across pteridophytes and consider future directions making recommendations along the way. From a comprehensive survey of the literature, a confused picture emerges: suggestions that members of the Lycopsida harbour Basidiomycota fungi contrast sharply with extensive cytological and recent molecular evidence pointing to exclusively Glomeromycota and/or Mucoromycotina associations in this group. Similarly, reports of dark septate, assumingly ascomycetous, hyphae in a range of pteridophytes, advocating a mutualistic relationship, are not backed by functional evidence and the fact that the fungus invariably occupies dead host tissue points to saprotrophy and not mutualism. The best conclusion that can be reached based on current evidence is that the fungal symbionts of pteridophytes belong to the two fungal lineages Mucoromycotina and Glomeromycota. Do symbiotic fungi and host pteridophytes engage in mutually beneficial partnerships? To date, only two pioneering studies have addressed this key question demonstrating reciprocal exchange of nutrients between the sporophytes of Ophioglossum vulgatum and Osmunda regalis and their fungal symbionts. There is a pressing need for more functional investigations also extending to the gametophyte generation and coupled with in vitro isolation and resynthesis studies to unravel the effect of the fungi on their host.

Key words: functional studies, fungal associations, Glomeromycota, Mucoromycotina, mutualisms, mycorrhizas, pteridophytes