Assessment Notes

Justification

Marsh Honey Fungus is a characteristic and rare Eurasian fungal species. It is confined to the specific types of wetlands with low nitrogen availability and at least localized base-rich microhabitats (or alkaline fens), usually having high plant diversity. Despite the occurrence of a large number of wetlands there are only small number suitable for the successful existence of Armillaria ectypa. Even insignificant changes of hydrological regime in and around fens can lead to extinction of this species. It is recorded from 16 countries, Red-listed in 11 countries. It is threatened by all kinds of actions leading to changes of hydrological regime and eutrophication. Artmillaria ectypa is assessed as Near Threatened  because of an estimated  population size reduction of  25% over the last 30 years (three generations), a decline suspected to continue and caused by habitat loss and degradation. This almost meets  the threshold for a Vulnerable listing under criteria A2c+3c+4c.

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Geographic range

Armillaria ectypa is a rare Eurasian species across its range, with most records  (>60) from Europe and with only a few (less than 10) localities in Western Siberia (Ainsworth 2003, Dahlberg and Croneborg 2003, Otto and Fraiture 2015). It is also recorded from Japan and China (Otto and Fraiture 2015).

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Population and Trends

This fungus appears to be extremely rare across Europe and Asia even within its habitat. It is certainly overlooked as observations of fungi rely on the presence of the irregular appearance of sporocarps. It is not a very distinctive species, but its specific habitat requirements facilitating the identification and in combination with it being pointed out as a nationally red-listed species in several countries  has spurred an interest among mycologist to search for it. Nevertheless, there are less than 60 known sites with Armillaria ectypa in Europe (Dahlberg and Croneborg, 2003, Otto and Fraiture 2015). In Russia, only six localities are known despite of intensive special investigation in some regions. In Japan less than 10 sites, small and considered as fragile habitats, are known.

It is nationally red-listed in 11 European countries (Austria, Czech Republic, Denmark, Finland, France (preliminary list), Germany, UK, Italy (preliminary list), Latvia, Netherlands  and Switzerland. Denmark has in total nine records of which only two are after 1990.  It is a priority species in UK were it is assessed as EN  (Ainsworth 2003). It is Regionally Extinct (RE) in Switzerland.

Trends in Russia are not known, but a threat to successful existence of localities is actual because of very small area of suitable habitats (for example in Tula region the bogs with A. ectypa are about 700 m² - 20,00m², and even the light damage of the bog can lead to change of hydrological mode and habitat in general.

The number of known sites of A. ectypa  in Europe and Asia are less than 75  and we estimate that the number of unknown localities not to exceed 10 times, e.g. the total no of sites not to exceed 750. The observed number of myclia (genetic individuals) per site is typically few  1-2 (-5).  It is possible to infer an estimate of the number of mature individuals using the recommendations of Dahlberg and Mueller (2011).  However, for this species, we are considering a  maximum of five mature individuals (ramets) per genet, so the total possible quantity have been estimated to possibly be less than 7,500 mature individuals.  

Population Trend: decreasing

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Habitat and Ecology

Marsh Honey Fungus is probably saprotrophic on decaying dead peat moss (Sphagnum spp.), sedges (Carex spp.), presumably also reeds (Phragmites australis).  In a few cases, when some woody  species has present, it has been  observed to form black rhizomorphs (M. Ainsworth pers. comm.).  It is easily distinguished as it lack  a ring on the stipe as all other Armillaria species in combination with its specific habitat;  wet and base rich habitats.  Armilaria  is confined to alkaline types of wetlands i.e. alkaline fens, ombrogenic peat bogs, sometimes reeds at paludified pond shores, and  paludous habitats near calcareous springs (Ainsworth 2003, Otto and Fraiture 2015). The habitats typically have low or rather low nitrogen contents. Alkaline fens are mires occupied by peat- or tufa-producing small sedge and brown moss communities developed on soils permanently waterlogged with calcareous water supply, and with minimal water level fluctuation. They are generally species-rich both in terms of mosses and flowering plant species (Šefferová Stanová et al. 2008).

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Threats

Wetland sites are threatened by all kinds of actions leading to changes of hydrological regime in and around mires such as peat and moss extraction, drainage ditch digging, extensive forestry plantations, eutrophication of groundwater, agricultural toxic discharges and the intensive cattle grazing nearby the habitats, etc.

Armillaria ectypa grows in alkaline fens which is a Natura 2000 habitat. Alkaline fens have been selectively drained in the past and have become very rare in most of EU countries and have a high conservation priority (Šefferová Stanová et al. 2008). These ecosystems are very sensitive to changes in hydrology and hydrochemistry in the wider area. For example, in Estonia the main trends in the distribution of communities of Caricetum davallianae over the last 35-40 years were evaluated and they were found to have decreased by more than 50 % (Šefferová Stanová et al. 2008). In the United Kingdom, it is estimated that 95-98 % of species-rich fens existing in 1940 have been lost. Similar losses have been reported in France and the Netherlands (Šefferová Stanová et al. 2008). Drainage schemes were particularly successful in the lowlands, where the majority of fens have been drained and transformed into agricultural land with limited potential for restoration. In a recent nation-wide inventory in Sweden, disturbed hydrology was reported on two thirds of the almost 1,600 alkaline fen sites with high nature conservation values identified, although for some of the sites the disturbance was marginal (Šefferová Stanová et al. 2008). It is concluded that majority of fens have been damaged and often changed into low productive meadows that cannot be maintained without management.

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Conservation Actions

Conservation management should focus on maintaining the appropriate site hydrology of sites with know occurrences of Armillaria ectypa. Fen management to manipulate structural diversity should avoid the destruction of good fruiting populations. The maintenance of appropriate hydrological regime, prevention of actions leading to drying, eutrophication and changing of water composition

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Use and Trade

The species is edible.

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Source and Citation

Svetasheva, T. 2015. Armillaria ectypa. The IUCN Red List of Threatened Species 2015: e.T75097245A75098379. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T75097245A75098379.en .Accessed on 2 February 2024

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• Country occurrence