BROAD VARIATION IN DEVELOPMENTAL AND MATURE BASIDIOME MORPHOLOGY OF THE ECTOMYCORRHIZAL FUNGUS HYDNANGIUM-SUBLAMELLATUM SP-NOV BRIDGES MORPHOLOGICALLY BASED GENERIC CONCEPTS OF HYDNANGIUM, PODOHYDNANGIUM AND LACCARIA

Ectomycorrhiza and basidiomes of Hydnangium sublamellatum sp. nov. wer e produced in pot cultures of Eucalyptus diversicolor and E. globulus seedlings which had been raised aseptically and inoculated with pure c ultures of the fungus. Ectomycorrhiza from these pot cultures are desc ribed. Basidiomes from the pot cultures and from the field are also de scribed, with particular emphasis on variation in basidiome macromorph ology. Basidiome variation of Hydnangium carneum and Laccaria fraterna from similar field sites and pot cultures is compared with that of H. sublamellatum. A large diversity in mature basidiome morphology, due to different developmental patterns, was observed amongst and within t he different pot culture and field collections of H. sublamellatum, ra nging from completely enclosed (angiocarpous) sublamellate to agaricoi d (hemiangiocarpous) lamellate forms. The diversity shown by H. sublam ellatum impinges upon morphologically based generic concepts of Hydnan gium (hypogeous or subepigeous, angiocarpous, truffle-like), Podohydna ngium (subepigeous, hemiangiocarpous) and Laccaria (epigeous, hemiangi ocarpous, agaricoid). Agaricoid basidiomes of H. sublamellatum approac h the macromorphology of Laccaria species, as both have a lamellate hy menium and hemiangiocarpous (hypovelangiocarpous) development, but H. sublamellatum is distinguished by not forcibly discharging its spores. An intermediate taxonomic position between Hydnangium and Podohydnang ium is suggested for H. sublamellatum, and we caution the present dist inction between those two genera. The radially arranged, sublamellate/ lamellate hymenium of H. sublamellatum is more similar to that of Podo hydnangium (partially exposed with some radial arrangement), than to t he usually loculate hymenium of Hydnangium. However, we place H. subla mellatum in Hydnangium on the basis of its stipe morphology (fragile a ttachment and small size), and observation of variations in H. carneum including some basidiomes having well-developed, emergent stipes. H. sublamellatum differs from H. carneum in developmental and mature macr omorphology of basidiomes, spore size and form, and number of sterigma ta on basidia. In addition to H. sublamellatum, substantial intraspeci fic variations in basidiome macromorphology were also observed with H. carneum and L. fraterna. For all three species, variations were not l ikely to be environmentally induced, as they were often expressed with in a single collection of basidiomes, and in all flushes of basidiomes throughout the season. The implications of broad, mature basidiome ph enotype plasticity within species are discussed for some generic conce pts in the Agaricales where fungi with extremely similar micromorpholo gy but with different mature basidiome structure are currently designa ted as representing separate genera. In particular, our investigation supports the hypothesis that there is a continuum of stipe, hymenium a nd pileus morphologies which transgresses the formal taxonomic boundar ies of Hydnangium, Podohydnangium and Laccaria.