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Chlorostroma vestlandicum B. Nordén & Læssøe

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Scientific name
Chlorostroma vestlandicum
Author
B. Nordén & Læssøe
Common names
safransnyltepute
хлорострома вестландская
IUCN Specialist Group
Cup-fungi, Truffles and Allies
Kingdom
Fungi
Phylum
Ascomycota
Class
Sordariomycetes
Order
Xylariales
Family
Xylariaceae
Assessment status
Assessed
Preliminary Category
EN C2a(i)
Proposed by
Thomas Læssøe
Assessors
John Bjarne Jordal, Björn Nordén, Thomas Læssøe, Ivona Kautmanova, A. Martyn Ainsworth, Armin Mešić
Editors
David Minter
Contributors
Tommy Knutsson
Comments etc.
James Westrip, John Bjarne Jordal (old account), Eugene Popov, Michael Krikorev
Reviewers
Anders Dahlberg

Assessment Notes

Justification

Chlorostroma vestlandicum was discovered in 2010 and described from western Norway in 2014. After surveying a large number of sites throughout western/southern Norway in the period 2011-2020 it is currently known from 23 sites (>1km apart). Recently, it was also discovered from 3 sites in western (European) Russia (E. Popov pers. comm.). Chlorostroma vestlandicum is a fairly conspicuous and characteristic stromatic pyrenomycete, and is probably a rare species with a limited distribution. It is a highly distinctive species due to a strikingly orange entostroma, a specialized association with the wood-decay fungus Hypoxylon vogesiacum, and only found in connection with this on dead wood of Ulmus glabra (wych elm). In Norway, H. vogesiacum and U. glabra are nationally red-listed as NT and EN respectively. The substrate and supposed fungal host of C. vestlandicum will in the future be declining in its main distribution area. Dutch Elm Desease (DED) affects so far only the populations in SE Norway (one locality, Vestfold) and has not spread to western Norway, but this disease is a significant future threat to C. vestlandicum in its entire distribution area.

There is an estimate of 150 localities in Norway. Outside Norway we estimate the species to be present in less than 100 localities. Assuming on average 10 mature individfuals/site, this gives an estimate of less than 2500 mature individuals globally.

Chlorostroma vestlandicum is assessed as EN in Norway and not evaluated in Russia. The known population is completely restricted to smaller parts of N. Europe. In its distribution range, it is considered to suffer from a decline in host trees and in the associated Hypoxylon vogesiacum by 15-30% during three generations in present and future (30 years) caused by fungal pathogens, red deer damage to elm trees, and competition from the invasive Acer pseudoplatanus. Ulmus glabra is therefore EN both in Norway (where the main known population of C. vestlandicum is) and in Europe as a whole. Chlorostroma vestlandicum is assessed as EN C2a (i) based on an estimated total population not exceeding 2500 individuals, ongoing reduction in habitat and population and small sub-populations (<250 individuals).


Taxonomic notes

The species belongs to a genus with two further species, both being parasites of Hypoxylon species.


Why suggested for a Global Red List Assessment?

This is a fairly conspicuous and characteristic stromatic pyrenomycete. Recently described, it is so far known only from western Norway, one place in SE Norway, and a locality near St Petersburg in W Russia. The species is a highly specialized parasite of the rare fungus Hypoxylon vogesiacum, a species that in turn mainly occurs on decaying trunks or branches of veteran trees of Ulmus glabra. Chlorostroma vestlandicum was described from coarse dead wood of Ulmus glabra in western Norway (Nordén et al. 2015). It has invariably been found in close association with Hypoxylon vogesiacum and appears to be parasitic on this species. With a strikingly orange entostroma, tiny perithecia and this specialized habitat association it is a highly distinctive species, which would have been discovered earlier if widely distributed. Its distribution seems to cover mainly the hemiboreal regions of western Norway, an area not yet affected by but threatened with Dutch elm disease. It is probably a rare species occurring only in localities rich in coarse dead wood with large populations of its host H. vogesiacum.


Geographic range

Chlorostroma vestlandicum is known from Norway and Russia. In Norway, 22 of 23 sites are lying in western Norway (including mid Norway). The last one is an isolated site in SE Norway. In addition three new records were recently found in European Russia not far from St Petersburg (E. Popov pers. comm.). Since C. vestlandicum is a prominent species it would have been described earlier if widely distributed in Europe. It most probably has a much narrower distribution than its host, possibly defined by climatic and/or historic factors.


Population and Trends

Chlorostroma vestlandicum was first found in W Norway in 2011. The host of Chlorostroma vestlandicum, the fungus Hypoxylon vogesiacum, is nationally red-listed in Norway as NT, while the tree, Ulmus glabra, which provides the dead wood on which parasitized H. vogesiacum grows, is nationally red-listed in Norway VU. Ulmus glabra has been estimated as having an ongoing decline of 30-50% (or maybe >50%) over 90 years. Hypoxylon vogesiacum has its largest European population in western parts of Norway, where old trees of Ulmus glabra not yet exposed to Dutch Elm Disease (DED) are still common. Hypoxylon vogesiacum is here estimated as having a decline of 15-30% in 30 years. Within Europe generally, populations of U. glabra are also declining (10-40% in the past century; >30% in the coming century), and the species is assessed as VU (Rivers 2017), while globally, Ulmus glabra is DD (Barstow & Rivers 2017). In Western Russia DED is present with serious impact on urban trees of U. glabra, but good data on wild populations of the tree are lacking (E. Popov pers. comm.). Based on this, C. vestlandicum is estimated to have an ongoing and future decline of 15-30% during 3 generations (30 years). Its habitat is under serious threats (see threats).

There are an estimated 150 localities of C. vestlandicum in Norway, based on many searches over the last 10 years. Outside Norway we suppose fewer than 100 localities. Applying the recommended template for assessing wood inhabiting fungi (10 individuals/site; Dahlberg & Mueller 2011) this results in an estimate of fewer than 2500 mature individuals.

Population Trend: Decreasing


Habitat and Ecology

Chlorostroma vestlandicum is be associated with, and probably parasitic on Hypoxylon vogesiacum. Its distribution and population size are probably partly delimited by the distribution and population size of its fungal host. Chlorostroma vestlandicum is found on coarse logs of old trees or on fallen branches of Ulmus glabra, or on dead parts of still living trees. Most Norwegian and at least one of the three Russian collections were associated with stromata of H. vogesiacum (E. Popov pers. comm.). According to currently available information, C. vestlandicum has a much narrower distribution than H. vogesiacum. All findings of C. vestlandicum in Norway were made in deciduous forests with U. glabra, up to 320 meters above sea level. The species (like its hosts) seems to prefer relatively warm summers. H. vogesiacum was described from France and is furthermore reported from Sweden, Finland, Austria, Switzerland, and Spain (additional records from North America and Asia could be other species), but C. vestlandicum has never been found in these countries. H. vogesiacum has a hemiboreal distribution in Nordic countries (Granmo et al. 1989, Granmo 1999, Nordén et al. 2014). In Norway, C. vestlandicum is distributed in the warmest parts of southern Norway north to Trøndelag, with its largest populations in western Norway, one of the few regions in Europe where Dutch Elm Disease is still absent.

Temperate Forest

Threats

The main threats are from the decline of suitable Ulmus logs due to change in habitat management and an increase in Red Deer population affecting re-establishments of new deciduous trees. Dutch Elm Disease (DED) is also an obvious threat which will kill all host trees if, as predicted, it reaches the habitats of Chlorostroma vestlandicum in western Norway (hitherto not discovered here). Such threats are intensified by the species’ small and fragmented population.

Other ecosystem modificationsNamed speciesNamed species

Conservation Actions

Both Ulmus glabra and H. vogesiacum are nationally red-listed and declining in Norway (as EN and NT respectively; Artsdatabanken 2021), and C. vestlandicum (EN in Norway) therefore warrants attention in conservation work. All known sites are in need of area-specific protection and management plans. The known localities are very rich in other rare and red-listed species. Monitoring the spread of DED is important to stop it from approaching the core area of distribution of Chlorostroma vestlandicum. Control of excessive red deer populations and halting spread of invasive Acer pseudoplatanus are also desirable.

Site/area protectionSite/area managementInvasive/problematic species controlHabitat & natural process restorationConservation payments

Research needed

More information is needed about the life strategy of Chlorostroma vestlandicum and its connection to H. vogesiacum. Since C. vestlandicum is a prominent species it would have been described earlier if widely distributed in Europe. It most probably has a much narrower distribution than its host, H. vogesiacum, and U. glabra, the key associated tree, and that narrower distribution is possibly defined by climatic, historical or ecological factors. Chlorostroma vestlandicum should be searched for in other areas with a similar climate in Europe. Hypoxylon vogesiacum is also found on other trees, including Fraxinus excelsior, but C. vestlandicum is only encountered on Ulmus glabra. Can it also live on other trees? Knowledge of the population dynamics of U. glabra and H. vogesiacum has many gaps which should be filled.

Population size, distribution & trendsPopulation trendsHabitat trends

Use and Trade

There is no use or trade of this species.


Bibliography

Artsdatabanken (2021). Norsk rødliste for arter 2021. (Red-listed species in Norway 2021).  Artsdatabanken, Trondheim. ISBN: 978-82-92838-56-3

Barstow, M. & Rivers, M.C. 2017. Ulmus glabra. The IUCN Red List of Threatened Species 2017: e.T61966807A61966819. http://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T61966807A61966819.en [global assessment]

Nordén, B., Læssøe, T. & Jordal, J.B. 2014. Chlorostroma vestlandicum sp. nov., a host-specific mycoparasite on Hypoxylon vogesiacum from western Norway. Karstenia 54: 9-13.

Rivers, M.C. 2017. Ulmus glabra. The IUCN Red List of Threatened Species 2017: e.T61966807A80570504. https://www.iucnredlist.org/species/61966807/80570504.  Downloaded on 05 March 2021. [Assessment for Europe].


Country occurrence

Regional Population and Trends

Country Trend Redlisted