Diagnosis: Hypocreopsis amplectens differt ab H. lichenoide, ascis (2-)3-4 sporis, ascosporis (20-)33-52(-112) x 9-13 µm, (1-)2-3(-7) septatis et pariete sporarum distincte verrucoso.

Etymology: refers to the distinctive grasping, finger-like lobes of the stroma on narrow-diameter twigs.

The Internal Transcribed Spacer region of the rDNA was identical between the New Zealand collection (Genbank accession number EU073198) and the one Australian collection sequenced (MEL 2032949, Genbank accession number EU073199). No other Hypocreopsis DNA sequences are available in Genbank. A BLAST search places H. amplectens among the Hypocreales, but with no clear relationship within the order.

Hypocreopsis amplectens is illustrated in colour by Fuhrer (2005), Grey & Grey (2005), May (2001), and McCann (2003). Stromata from the different collections are of similar overall appearance but the radiating "fingers" are narrower and more numerous in the single New Zealand collection than those in most Australian collections. Stromata are appressed to the substrate. On larger diameter wood, the lobes remain adjacent, but on smaller diameter wood the lobes extend like clasping fingers around the substrate and may interlace.

In Australasia, the only previous record of Hypocreopsis (Hood 2003) is of a collection with affinities to H. episphaeria, forming minute, pulvinate stromata on Corymbia wood in Queensland. Among species of Hypocrea from Australasia, H. cerebriformis Berk. was noted by Cooke (1892) as having stromata that are "lobed". The illustration of the type by Lloyd (1924) shows that the lobes do not radiate from a common centre, as in Hypocreopsis amplectens, and he described 16-spored asci with spores globose to cubical, which is consistent with the typical 8-spored ascus of Hypocrea, where each ascospore breaks into 2 part-spores.

The loose, globose cells on the surface of the stromata of H. amplectens appear to be similar in shape and size to the structures illustrated as conidia by Strid (1967) for H. lichenoides. However, the palisade of conidiogenous cells described by Strid was not observed in the Australasian fungus. The asci of H. amplectens are initially 4-spored, although often one of the spores aborts. As the spores mature in the asci they develop 2 or 3 septa and the spore walls become coarsely ornamented and thickened. In some cases adjacent spores appear to fuse as the wall thickening develops, and consequently the mature asci are 2-spored, one of the spores having 5 or 6 septa. Candy & Webster (1988) illustrated and described a similar fusing of ascospores in H. rhododendri.

Hypocreopsis lichenoides and H. rhododendri are commonly found in association with Hymenochaete fruiting bodies (Cauchon & Ouellette 1964; Candy & Webster 1988), and are possibly parasitic on the Hymenochaete. All Australian collections of Hypocreopsis amplectens have been associated with Hymenochaete, mostly on heath tea-tree (Leptospermum myrsinoides), a common and widespread shrub on sandy soils in south-eastern Australia. However, at the sites where Hypocreopsis has been observed, the shrubs are in over-mature stands, which appear to have been long unburnt. The tea-tree host is multi-stemmed and commonly has dead standing branches as well as numerous fallen dead branches. Hypocreopsis occurs on both the standing and fallen dead branches. Stands of heath tea-tree occur among a mosaic of Eucalyptus heathy woodland and thickets of Melaleuca squarrosa. Fire is an important factor in the dynamics of these vegetation communities. Wildfires are a relatively common occurrence, and, therefore, long unburnt stands may well be quite rare.

In Victoria, Australia Hypocreopsis amplectens has been classified as "vulnerable" (as Hypocreopsis sp. or Hypocreopsis sp. 'Nyora') and is formally listed under the Flora and Fauna Guarantee Act 1988. The Nyora Flora and Fauna Reserve was created partly because of the occurrence of H. amplectens (Buchanan & May 2003). Despite intensive surveys, including it being one of the target species of the Fungimap scheme (Grey & Grey 2005), H. amplectens is still known from only three sites in Australia, within a 75-km radius in southern Victoria (May 2001; Grey & Grey 2005). It has been collected only once in New Zealand, more than 20 years ago. The collection was made in a readily accessible patch of Nothofagus forest, quite regularly visited by mycologists. Similar forests are widespread through the South Island of New Zealand, and these have been sampled intensively for Hypocreales over many years. H. amplectens has distinctive, quite large fruiting bodies and must, therefore, be considered rare.

The association with Hymenochaete, in combination with the apparent requirement for long unburnt stands of heath tea-tree, are no doubt contributing factors to the rarity of Hypocreopsis amplectens in Australia, but why the species is rare in New Zealand needs further investigation. The identity of the host Hymenochaete is not known, nor is its host range, but if Hypocreopsis amplectens were to any degree limited to its fungal host, this would be a further contributing factor to its rarity. No fungal host was observed in the New Zealand specimen.

The Northern Hemisphere Hypocreopsis lichenoides and H. rhododendri are included in several lists of rare and threatened fungi. Both species are dealt with as "species of conservation concern" in the UK Government Biodiversity Action Plan (Ainsworth 2003). Hypocreopsis lichenoides was considered by Strid (1967) to be a rare fungus in Europe and North America, although Niemelä & Nordin (1985) reported an apparent recent expansion in range and frequency for the species in Scandinavia, possibly due to climatic changes. The rarity of H. amplectens in Australia and New Zealand, and the likelihood that specific habitat and substrate requirements limit occurrence and distribution, mean that the species should be considered for listing under the Australian Environment Protection Biodiversity Conservation Act 1999 and the New Zealand threat classification system (Molloy et al. 2002).