R-L categories correct, but text here does not match final assessment. Updated version will be published in IUCN´s Red List June or Nov 2019.
European endemic resembling a small oyster mushroom almost always found fruiting at the base of dead Ammophila in coastal sand dunes with most populations recorded around the Atlantic and North Sea coastlines. Recently distinguished from H. bonii which can have larger fruitbodies and can co-occur. Eight countries with records since 1980. and ca. 45 sites are known (likely to be close to the number of known occupied clumps of Ammophila). Applying Criterion C, using an estimate of <10,000 mature individuals in total, but fewer than 250 mature individuals in each subpopulation, and accepting a continuing decline in habitat quality from continued trampling of dunes and their conversion to other uses (golf courses, caravan sites, more permanent housing) produces an assessment of VU C2a(i)
Assumptions: 2 genets inside each Ammophila clump and a similar number of ramets per genet. The sites I’ve surveyed had only one to few occupied clumps so if we estimate 5 occupied clumps per site and apply x10 to estimate the true number of sites (and this seems a high estimate) we reach 9000 mature individuals in total.
Two marram oyster species (Ainsworth et al. 2016) now recognised as present in France, UK and the Netherlands (this last country added on basis of Flickr report of a redetermination of a “culmicola” collection). When available collections are checked, this could diminish the number of historic records of H. culmicola s.str.
Anders to Martyn (now addressed): Qualify for EN or VU, no of known mature individuals (45 locations corresponds to 450 mature individuals if max 1 genotype/site). Hoe many times more locations do you estimate is present? Now the estimate is not more than x 5 (if two or more genotypes/site, fewer sites).
Martyn to Anders: I don’t think there will be 10 ramets per genet - I think there are few (1 or 2) genets inside each Ammophila clump and a similar number of ramets per genet. The sites I’ve surveyed had only one to few occupied clumps (fruiting patches) so if we estimate 5 occupied clumps per site then even if we have x10 for estimate of true number of sites (and this seems a high estimate) we reach 9000 mature individuals which is within VU.
Restricted to coastal Ammophila stands particularly around Atlantic and North Sea coasts (one outpost locality in inland dunes in Hungary: Fraiture & Otto (2015) and A. Fraiture in litt.)
Dahlberg & Croneborg (2003) documented 6 countries with records since 1980 and Spain and Hungary (1 collection) can now be added to this list (Fraiture & Otto 2015 and A. Fraiture in litt.). It has also been reported from the Italian Adriatic coast (Pacioni 1986). If pre-1980 records are included, then the range also includes the Republic of Ireland (Dahlberg & Croneborg 2003). Data on fruiting abundance is lacking (numbers of occupied Ammophila plants or ramets), however there are ca. 45 fruiting patches recorded (equivalent to a maximum AOO of ca.180km2). Considered red-listed in around half of the countries of occurrence, thought to be extinct in Ireland. Although there is some evidence of habitat decline at some occupied localities, mainly due to changing land usage on coastal dunes and tourist pressures, evidence of a quantified decline is lacking, thus ruling out Criterion A. May possibly qualify for Criterion B since ca. 45 fruiting patches are known to have been recorded (equivalent to a maximum AOO of ca.180km2) but this species is generally not found unless as a result of deliberate and comprehensive sand dune surveys. It forms relatively inconspicuous mushrooms that are likely to have been overlooked due to small size, dark colour and restricted microhabitat. Such dedicated survey work has been carried out in the Netherlands (E.J.M. Arnolds pers. comm.) and UK (Lost & Found Fungi Project: 4yrs’ search yielded no records). Therefore there are considerable doubts remaining concerning its true distribution (whether it qualifies for “severely fragmented”) and its population size. Some historic records could be of the recently described species H. bonii which can co-occur with H. culmicola s.str. Criterion C seems most readily appropriate, using an estimate of <10,000 mature individuals in total, but less than 1000 mature individuals in each subpopulation, and accepting a continuing decline in habitat quality from continued trampling of dunes and their conversion to other uses (golf courses, caravan sites, more permanent housing).
Population Trend: Decreasing
Coastal sand dunes, rarely inland dunes growing saprotrophically on Ammophila (possibly also on other Poaceae in same habitat such as Leymus arenarius, which was recorded at one English site). Narrow niche requirements, i.e. dynamic sand dune ecosystems with sparse vegetation of herbs and grasses.
Threats are mainly from conversion of coastal dunes to caravan/camping sites, golf courses or other development and, on a slower timescale, to visitor pressure and recreational disturbance (trampling). Changes in large-scale offshore dredging activities are also suspected to alter coastal dynamics unfavourably for this species, for example by shifting the prevailing deposition from sand to pebbles and shingle accretion (Kent, UK). Storm surges and long-term sea level rise, coupled with the associated coastal management responses, present a clear threat to dynamic dune systems upon which this species depends.
Inland dune systems are under even higher threats of overgrowth, tree plantations and other changes of land use causing changes in edaphic and vegetation composition.
Further research needed to inform practical conservation action
The main focus of research should be on further systematic survey of suitable habitat and checking of historic collections to determine whether redetermination as H. bonii is required. Surveillance is also important to reveal how its fruiting presence (size and location of occupied grass culms/roots) changes from year to year to assess how ruderal this species is. Population genetics required to estimate the number of genets per plant and to locate the whereabouts of the fungus within the plant (root systems or separate stems). Further ecological research is required to determine whether particular Ammophila-dominated habitats are favoured.
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