Liverworts to the rescue: an investigation of their efficacy as mycorrhizal inoculum for vascular plants

Pezoloma ericae (D.J. Read) Baral, a widespread mycorrhizal fungus of plants in the Ericales, is known to form intracellular associations with several families of leafy liverworts (Schistochilaceae, Lepidoziaceae, Cephaloziaceae, Cephaloziellaceae) in vitro. The ecological significance of this link between vascular and non‐vascular plants is unknown. Fungal symbionts were isolated from rhizoids of the leafy liverworts Cephalozia connivens (Dicks.) Lindb. and C. bicuspidata (L.) Dum. (Cephaloziaceae), as well as from the hair roots of two dominant ericoid mycorrhiza‐forming species of European heathlands, Erica tetralix (L.) and Calluna vulgaris (L.). Using pure cultures of P. ericae, we resynthesized liverwort–fungus associations to use colonized liverworts as inoculum which was applied to substrates supporting the growth of heather seedlings and cuttings. Effects were quantified using germination, rooting, plant colonization, plant survival under waterlogging stress and growth in height in experimental systems with and without liverworts and/or fungi. Fungal symbionts growing from liverwort rhizoids readily colonized the hair roots of ericaceous plants to form typical ericoid mycorrhizas. The presence of inoculum‐bearing liverworts led to significant increases in plant growth. Erica tetralix was more responsive to inoculation than C. vulgaris. Ericaceous cuttings rooted and survived more successfully when they were coplanted with previously colonized liverwort stems. We demonstrate, under realistic ecological circumstances, that liverworts can deliver mycorrhizal inoculum and improve the establishment of vascular plants. We propose that by providing sources of mycorrhizal inoculum, symbiotic non‐vascular plants can contribute to the restoration of plant communities dominated by Ericales plants. This research leads to broader knowledge about the function of ericoid mycorrhizas in ecosystems.