Geastrum britannicum (Vaulted Earthstar) – a nice find
It’s always good to find something new, better when it is unexpected and better still in January, a month that generally comes last in “Best Month of the Year” competitions.
The surprise highlight of a walk yesterday was the Vaulted Earthstar fungus, Geastrum britannicum.
My friend Sarah and I were walking along a minor road just outside Norwich when we both noticed some Earthstars growing on soil on the verge, amongst Ivy, beneath trees. We both spotted the fungi at the same time and I took a series of photos.
Geastrum britannicum
I wasn’t sure which Earthstar we’d found, so when I came home I shared my pictures on Facebook with members of Norfolk Fungus Study Group. One of the group members, Jonathan Revett, identified them for me as Geastrum britannicum.
Jonathan is very familiar with the species, having found the first specimens on a roadside verge beneath pine trees in Cockley Cley in the Norfolk Brecks, in 2000. The nearest fit appeared to be the Rayed Earthstar, Geastrum quadrifidum, though they didn’t look quite right. In subsequent years, further forays elsewhere in Norfolk and in Hampshire, Powys and Shropshire found more of the unusual fungi. They consistently had small spores (3 – 3.5 micrometres), smaller than all the other British species of Earthstar (note 1).
Samples of the fungi were sent to Kew Gardens for its Mycology Collection and several years later they were looked at by a Spanish team comparing gene sequences in Geastrum, including the PhD student Juan Carlos Zamora (note 2). As a result, in 2015 the fungus was recognised as a new species, and given the name Geastrum britannicum because it had only been found in the British Isles .
When I originally wrote this in January 2021, Geastrum britannicum didn’t have an official name but three years later (February 2024) it is known as the Vaulted Earthstar.
It seems that the species is not necessarily rare, just overlooked (note 3). Specimens in other collections have been checked and the Kew database now contains records from ten different samples, the earliest taken in 1994 (note 4).
I have cycled by the site where we saw yesterday’s earthstars on many occasions without realising that I was passing hidden treasure. It pays to look more closely.
Below are some more of my photographs of Geastrum britannicum. More photos can be found online on Jonathan Revett’s Fenfungi website, in this Business Insider article (also Jonathan’s photos) and on the Nature Picture Library website (photo by Adrian Davies).
Notes
Note 1 – See page 9 in the Herefordshire Fungus Survey Group News Sheet No. 29, Spring 2015. The newsletter gives the background to the discovery and a useful summary of the identification characteristics:
- Erect, grooved pointed ‘beak’ when fresh
- Distinct halo around the beak which is surrounded by a rim
- Sac may be coated with fine mica-like scurf
- Sac may have a hanging collar-like shape at the bottom
- Sac is raised on a stalk
- 4 – 5 ERECT ‘legs’
- Whole structure standing on a saucer of matted hyphae and debris
- Habitat: mostly under churchyard yews, but also known under roadside oak and pine.
The news sheet also states that “It is the combination of these characters that is important. If only one or two characters are present, your find may be G. fornicatum, striatum, quadrifidum, or even berkleyii. If you think you have found G. britannicum, examination of the spores is essential as they are smaller than all other UK species.”
Jonathan Revett commented on my photos: “Key features are the arching arms and a fimbriate not beaked mouth which is delimited (halo around base of beak). They also seem to enjoy growing in churchyards often in large numbers”.
Note 2 – See “Integrative taxonomy reveals an unexpected diversity in Geastrum section Geastrum (Geastrales, Basidiomycota)“. J.C. Zamora, F.D. Calonge, M.P. Martín. Persoonia vol. 34: pp130–165 (2015). The whole paper can be downloaded for free as a PDF (which I wish was possible more often.)
Note 3 – See “Geastrum britannicum – a surprisingly common new species in Britain“. Brian Spooner, Alick Henrici, A. Martyn Ainsworth. Field Mycology, vol. 16, issue 2, pp54 – 57 (2015).
Note 4 – From an online search of the Mycology Collection using “Geastrum britannicum” in the ‘Taxon’ field. All the samples were found growing on soil, sometimes in leaf litter, under a variety of trees.