Arthonia anglica Refound in the New Forest


The run of new significant discoveries and rediscoveries of lichens in the New Forest woodlands reported in March 2016 has continued. On the 12th of April 2016 I was having another a casual lunch time dog walk, this time in Matley Wood (SU3307).

I was not intending looking at the lichens much but could not pass one lovely looking old Holly pollard without having a quick look. This had several nice Arthonia astroidestera NT (NS/IR) thalli, a frequent species on Holly in this wood, with stellate apothecia partly covered in white priuna. However, below one clear Arthonia astroidestera thallus was another without any sign of pruina. Arthonia astroidestera can lose most of its pruina but this thallus did not look like right, so I took a little sample.

The Holly

Back home, illuminating the specimen with a UV lamp produced no trace of bright orange fluorescence, so it was not Arthonia astroidestera. I made a section in which I found no spores but, to confirm my hunch about what this might be, flushed some C in: YES an fleeting red effusion from, the apothecia. Finally a second section produced a spore, and confirmed the identification; an old brown spore 20 x 6µm, three septate with an enlarge end cell. Arthonia anglica EN (NR/IR/S41)! Last collected from the New Forest in 1868 by Crombie and not seen anywhere in England since 1998, when it was collected by Brain and Sandy Coppins at at Sloo Wood, Peppercombe, North Devon.

The specimen

This appears to be a rare species in Europe. In England there have only been two historic collections, the 1868 New Forest collection and the original collection, probably by Borrer from St Leonard's Forest, Sussex in 1806. Recently it has been recorded from Holly at Peppercombe, North Devon, between 1976 and 1998 and once from an unlocalised Ash at Millook, North Cornwall by Francis Rose in 1989 (a trip where I was present, but certainly did not see the collection and I have been looking for it ever since!). A search of the internet indicates that in Europe it has also been recorded in the Azores and in Portugal. It appears more frequently recorded in eastern USA and the Mushroom Observer site has some pictures. It has also been recorded from Rwanda, so it is also in the tropics.

I revisited at lunchtime on the 12th of April 2016 to record some more details but found no more Arthonia anglica thalli on the tree.

Arthonia anglica: a single thallus, 10 x 5cm with Enterographa crassa, Mycoporum lacteum NT (NS), Opegrapha vulgata and Thelotrema lepadinum, with Arthonia astroidestera NT (NS/IR) nearby.

Also on bark on the tree: Anisomeridium ranunculosporum, Cresponea premnea Nb (IR), Lecanactis abietina, Schismatomma decolorans, Mycoporum antecellens, Pertusaria leioplaca, Phaeographis dendritica, Schismatomma niveum Nb (IR) and Stenocybe septata Nb (IR).

Inside the trunk, on lignum were Ramonia nigra CR (NR/IR/S41), new to the wood, and an unknown Melaspilea species: disk very dark brown, flat, even and round & 0.45 – 0.74mm diam; exciple, epithecium and hypothecium reddish brown in water but are K + bright green, fading to olive; hymenium K/I + blue; spores brown, one septate, sole shaped & 14 – 17 x 5 – 6µm. This looks interesting; I have collected it from an ancient Holly in a ravine in Wales and previously in the New Forest, also from the inside old Hollies.

Melaspilea species

An adjacent Holly had Bacidia incompta VU (NS/IR/S42) inside an hollow trunk and another had a visible Calicium diploellum CR (NR/IR/BAP) pinhead in a lenticel; an amazing Holly grove!

Finally on the way back I spotted what looked very like Pertusaria pustulata VU (NR), on an old Beech, also new to the wood, but, in this case, also the 10km national grid square. In Pertusaria pustulata the fertile wart has only a single pore, which is irregular and torn looking, so clearly not Pertusaria pertusa. The wort is also not as open as Pertusaria hymenea but is more robust and open than Pertusaria leioplaca. A neat field test is that the thallus is K + yellow and C + yellow, a combination not seen with any of the look alikes. Under the microscope the asci have only two spores each this, combined with the spores sizes and the ornamentation on the spore wall, is definitive. The Matley Wood lichen checked out as Pertusaria pustulata, with two spores per asci, spores 87 – 90 x 30µm, and with the distinctive cell wall ornamentation.

Pertusaria pustulata on old Beech

Neil A Sanderson 15/4/2016

Update

Andy Cross and I went back on the afternoon of Saturday the 16th April, to have a look around the area where Arthonia anglica was found. We did not find any more Arthonia anglica, but did find lots of lichen interest on Holly. Near to the original Holly, a second Ramonia nigra CR (NR/IR/S41) colony was found inside a hollow Holly picture. We also found five Hollies with Bacidia incompta VU (NS/IR/S41) picture, five with Arthonia astroidestera NT (NS/IR), one colony of Melaspilea lentiginosa NT (NS/IR/S41) on Phaeographis dendritica and Ramonia chrysophaea NT (NS/IR/IR) on one Holly on lignum. One oddity was Opegrapha corticola Nb (IR) on old Holly; something I have only recorded on Holly from Matley Wood. Old Oak added Enterographa sorediata NT (NS/IR/S41) on the dry bark of an old tree.

The big find however, was made at the end of the survey when Andy diverted on to some young Sweet Chestnut trees. These are the offspring trees planted in the 1890s when a number of different ornamental tree species were planted into Matley Wood. Mostly the Matley Chestnuts, including the 125 years old original trees, are very dull for lichens; typical of most Sweet Chestnuts in Britain. Andy, however, did find something odd; he was thinking Schismatomma as the apothecia reminded him of some fertile Schismatomma decolorans I had shown him a few years ago. I went over and had a look and was impressed: this was a huge colony of Schismatomma graphidioides VU (NR/IR/S41)! The third site in the New Forest and fourth tree, and by far the largest colony in the Forest.

The serpentine and branched young apothecia, swelling to irregular rounded apothecia when more mature, with pale raised thalline margins, were unmistakable. There can be confusion with Opegrapha rufescens; this does have a whitened band of thallus around the apothecia, but this is not raised and the apothecia are normally relatively simple lirelli. Basically if there is doubt it is usually Opegrapha rufescens! Internally the apothecia differences are subtile, but the K and K/I reactions are different. There is a good account of the differences between the apothecia at the Lichens of Wales site.

Schismatomma graphidioides on Sweet Chestnut

The Schismatomma graphidioides was frequent in a transition to the dry side of the tree, with Lecanactis abietina abundant along with Arthonia spadicea, Cliostomum flavidulum Nb (NS), Graphis elegans, Schismatomma niveum Nb (IR), Schismatomma quercicola Nb (IR), Thelotrema lepadinum and Arthonia invadens NT (NS/IR/S41) on Schismatomma quercicola. This was a more acidic habitat than I had seen Schismatomma graphidioides on before. Previously in the New Forest and the south west, the colonies I have seen on trees were in similar situations, also with Lecanactis abietina dominant, but with Pyrenula chlorospila as an associated species; much less acid. However, the ITALIC website lists the pH range as "pH of the substrata: intermediate between very acid and subneutral (2) to subneutral (3)". The acid end of this range would fit the Matley Wood colony. Sweet Chestnut also appears to be a new substrate for Schismatomma graphidioides in Britain.

The species is very rare and scattered in England and Wales, and appears to turn up at random, often on otherwise rather ordinary trees. Not an easy ecology to understand.

I went back on the Sunday afternoon to get some more photographs, and then did some reconnaissance to the north. In another area of high quality Hollies, I spotted a second Schismatomma graphidioides colony, this time on an old Holly; another new substate for the species in Britain. These had less well developed apothecia, but some raised thalli margins to the apothecia could be seen. I checked a small sample microscopically this time; no mature spores, but the exciple was not visible, epithecium reddish brown K + intensifying slightly, K/I + blue, with the bluing extending into hymenium, hypothecium brown and K + dark olive green. Paraphyses abundant and slender. The lichen was frequent as small patches over 0.25 x 1m with abundant Thelotrema lepadinum, along with Graphis elegans, Loxospora elatina, Mycoporum lacteum NT (NS) and Pertusaria leioplaca. The community was on wetter bark than on the Chestnut, but was clearly also quite acid. When I found this species on smooth bark on Hornbeam in the Lake District it was also on wetter, if less acidic, bark, so possibly Schismatomma graphidioides might inhabit wetter situations on smooth bark.

Schismatomma graphidioides on Holly

Neil A Sanderson 21/4/2016

I have appended a species lists for Holly in Matley Wood and the whole New Forest that I will update as exploration proceeds (last update 16/9/2017).

Key Conservation Status
CR = Critically Endangered Red Data Book Species
EN = Endangered Red Data Book Species
VU = Vulnerable Red Data Book Species
NT = Near Threatened Red Data Book Species
NR = Nationally Rare
NS = Nationally Scarce
IR = International Responsibility species
Nb = Notable species NR, NS, IR or DD species which are not RDB Near Threatened species or higher.