Abstract Detail

Bryological and Lichenological Section/ABLS

Duckett, Jeffrey G. [1], Carafa, Anna [2], Ligrone, Roberto [2].

Liverwort Phylogeny and Endophytic Fungi.

As in the basal lineages of vascular plants (including Devonian fossils, Lycopodium, Psilotum and eusporangiate ferns), glomeromycotean fungi are widespread in the Marchantiales, Metzgeriales and Anthocerotales. Since the Glomeromycota are considered the archetypal fungi that invaded land together with archegoniate plants these are almost certainly the most primitive of all terrestrial fungal symbioses. Most striking are the associations in Haplomitrium and Treubia where the fungi are partially extracellular, associated with the secretion of voluminous quantities of mucilage and produce prominent hyphal swellings unknown in other VAs. The first sequence data from marchantialean endophytes suggests the presence of two distinct fungi, (tentatively assigned to different species in the genus Glomus) within the same thalli of Conocephalum, thus mirroring the VA infections in the nodules of the ancient gymnosperm family the Podocarpaceae. In contrast, the basidiomycetes found in the Aneuroceae, including an endophyte in Cryptothallus that forms ectomycorrhizas with Betula, and cytologically closely similar to orchidaceous mycorrhizas, appear to be of much more recent origins. Basidiomycetous associations, resembling monotropoid mycorrhizas, in the Lophoziaceae and Scapaniaceae reinforce molecular evidence indicating close affinities between these families. Whereas these basidiomycetes, plus those in the Arnelliaceae and Geocalycaceae have been shown in cross-infection experiments, to be host specific, the ascomycetes found in the swollen rhizoids of the Cephaloziaceae and allied families have a wide host range even extending to the formation of typical mycorrhizas with the Ericaceae. Absence of fungi in advanced liverwort families and particularly the Lejeuneaceae is most likely secondary loss. The absence of fungal symbioses of any kind in mosses is probably due to their high-branched multicellular rhizoids. Their ultimate ramifications, with diameters similar to mycorrhizal fungal hyphae, form a much more effective nutrient-scavenging system that their unicellular counterparts in hepatics.

1 - Queen Mary, University of London, School of Biological Sciences, London, E1 4NS, UK
2 - Seconda Universita' di Napoli, Facolta' di Scienze Ambientali, via Vivaldi 43, Caserta, I - 81100, Italy

Keywords:
basidiomycetes
Glomeromycota
host-specificity
mycorrhizas
symbiosis.

Presentation Type: Paper
Session: 35-1
Location: Ballroom 3 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 2:00 PM
Abstract ID:431