Hygrocybe is a genus of agarics in the familyHygrophoraceae. Called waxcaps in English, basidiocarps are often brightly coloured and have waxy to slimy caps, white spores, and smooth, ringless stems. In Europe they are characteristic of old, unimproved grasslands which are a declining habitat, making many Hygrocybe species of conservation concern. Elsewhere they are more typically found in woodlands. Most are ground-dwelling and all are believed to be moss associates. Around 150 species are recognized worldwide. Fruit bodies of several Hygrocybe species are considered edible and are sometimes offered for sale in local markets.
Taxonomy
History
Hygrocybe was first published in 1821 by Swedish mycologistElias Magnus Fries as a subsection of Agaricus and in 1871 was raised to the rank of genus by Kummer. In several papers, Karsten and Murrill used the name Hydrocybe, but this is now taken as an orthographic variant of Hygrocybe. The generic name is derived from the Greek ῦγρὁς + κυβη. Despite its comparatively early publication, the genus Hygrocybe was not widely accepted until the 1970s, most previous authors treating it as a synonym of Hygrophorus, a related genus of ectomycorrhizal agarics. Hygrocybe itself has been split into subgenera, several of which – notably Cuphophyllus and Gliophorus Herink – have subsequently been raised to generic rank. Some species, such as the mauve splitting waxcap, have been described in the small genus Humidicutis.
Current status
Recent molecular research, based on cladistic analysis of DNA sequences, suggests that Hygrocybe as currently understood is paraphyletic and does not form a single clade within the Hygrophoraceae. As a result, the genus Cuphophyllus was removed from Hygrocybe sensu stricto, together with the genus Gliophorus and several other genera.
Description
Fruit bodies of Hygrocybe species are all agaricoid, most having smooth to slightly scaly caps that are convex to conical and waxy to slimy when damp. Many are brightly coloured in shades of red, orange, or yellow – less commonly pink or green. Where present, the gills beneath the cap are often equally coloured and usually distant, thick, and waxy. One atypical South American species, Hygrocybe aphylla, lacks gills. The stems of Hygrocybe species lack a ring. The spore print is white. Fruit bodies of some species, notably Hygrocybe conica, blacken with age or when bruised. Microscopically, Hygrocybe species lack true cystidia and have comparatively large, smooth, inamyloidbasidiospores.
Habitat, nutrition, and distribution
Most species of Hygrocybe are soil-dwelling, though a few are only known from mossy tree trunks or logs. In Europe, species are typical of unimproved, short-sward grasslands, often termed "waxcap grasslands", but elsewhere they are more commonly found in woodland. Their metabolism has long been debated, but recent research suggests that they are not saprotrophic but rather symbiotically associated the roots of higher plants or mosses. Hyphae of H. conica have been detected in plant roots and other waxcap species have been detected as systemic endophytes of Plantago lanceolata. Species are distributed worldwide, from the tropics to the sub-polar regions. Around 150 have been described to date. Waxcaps receive most attention in northern Europe, where they are found in nutrient-poor pastures. However, outside Europe, waxcaps are more commonly associated with woodland habitats, for example the sclerophyll forests site at Lane Cove Bushland Park and Ferndale Park, Sydney.
Conservation
In Europe, waxcap grasslands and their associated fungi are of conservation concern, since unimproved grasslands have declined dramatically as a result of changes in agricultural practice. As a result, by 1993, 89% of European Hygrocybe species appeared on one or more national red lists of threatened fungi. In several countries, action has been taken to conserve waxcap grasslands and some of the rarer Hygrocybe species. Guidance In the United Kingdom, some grasslands have gained a measure of legal protection as Sites of Special Scientific Interest because of their waxcap interest, notably Llanishen Reservoir in Cardiff, where the original SSSI notification by the Countryside Council for Wales in 2006 was upheld following judicial review.
Economic usage
Because Hygrocybe species cannot be maintained in culture, none is cultivated commercially. Fruit bodies of a few species are considered edible in eastern Europe, south-east Asia, and Central America and are collected and consumed locally.
Literature
No comprehensive monograph of the genus has yet been published. In Europe, however, species of Hygrocybe have been illustrated and described in a standard English-language guide by Boertmann and also in an Italian guide by Candusso. European species have also been covered, more briefly, in descriptive French keys by Bon. Dutch species were illustrated and described by Arnolds. No equivalent modern guides have been published for North America, the most recent being by Hesler & Smith. There is, however, a guide to Californian species by Largent. In Australia, Hygrocybe species have been illustrated and described by Young and in New Zealand by Horak.
