Basidiomycetous endophytes in New Zealand Aneuraceae (simple thalloid liverworts, Metzgeriidae) and the derived status of the monotypic genus Verdoornia

Abstract

The ultrastructure of endophytic basidiomycetes in two New Zealand species of Aneura and the endemic genus Verdoornia is compared with that in northern hemisphere members of the Aneuraceae. The discovery of a basidiomycete colonization in Verdoornia and a reappraisal of earlier morphological data confirms molecular evidence that this is a derived genus nested within the Aneuraceae rather than a primitive isolated taxon, as considered previously. Throughout the Aneuraceae, the basidiomycetes exhibit similar colonization patterns; initial proliferation of dikaryotic, non-clamp-forming hyphal coils within the host cells is followed by senescence and aggregation of collapsed hyphae into large masses. Multiple cycles of colonization are common. Dolipores with imperforate parenthesomes indicate that the fungi are all heterobasidiomycetes. In line with earlier cross-colonization experiments showing complete host specificity, differences in hyphal diameters and dolipore dimensions suggest that the fungi belong to different taxa. The New Zealand aneuracean fungi have multilayered walls similar to their northern hemisphere counterparts. Within the Aneuraceae there appears to be a trend from very limited or no endophyte colonization in Riccardia to colonization of the entire thallus in Cryptothallus. The cytology of the fungal associations in Aneura and Verdoornia is highly suggestive of mixotrophy.