Hypotrachyna lividescens New to Britian

In August 2023 Andy Cross and I ventured off the New Forest and did some lichen recording on a nice relic patch of herb rich heath south of Romsey at Baddesley Common, a Hampshire Wildlife Trust nature reserve. This was giving us a reasonable but not spectacular list from scattered trees and bushes left in herb rich floodplain grassland, when I spotted something distinctly odd. First there was a small odd looking Hypotrachyna on a Sallow twig and then lots of the same thing on an isolated Birch.

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The Hypotrachyna with Hypogymnia physodes, Parmelia sulcata and Flavoparmelia caperata

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A more mature patch of the Hypotrachyna, with some young Hypotrachyna afrorevoluta to the left.

Compared to the Hypotrachyna afrorevoluta and Hypotrachyna revoluta s. str. on the Birch, it was was a paler ash-grey in colour and had very distinct compact hemispherical pale grey-greenish soralia. These gave it an attractive look and it did not look like anything I had seen before. Anyway I bagged some and carried on with the survey.

Back home a closer look gave the following description: thallus ash-grey in colour, lobes with rounded sinuses; hemispherical pale grey-greenish soralia, situated just below the apices or occasionally laminal; medulla C+ red then fading to orange-red; rhizines short but much dichotomously branched.

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Specimen

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Soralia

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Rhizines

The short but much dichotomously branched rhizines were particularly distinct, this ruled out an odd form of Hypotrachyna revoluta s. str. It turns out there are several tropical/warm temperate Hypotrachyna species colonising the south west of France and a handy key has been produced https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjojJ2AxeWEAxWnW0EAHYU_BEwQFnoECBEQAQ&url=https%3A%2F%2Fsciencepress.mnhn.fr%2Fen%2Fperiodiques%2Fmycologie%2F26%2F3%2Ftaxinomie-ecologie-et-chorologie-des-especes-francaises-des-genres-hypotrachyna-et-parmelinopsis-ascomycota-lichenises-parmeliaceae&usg=AOvVaw3xRhQyiIv9hMK6tqTyiaOh&opi=89978449” class=”bbcode_url”>https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjojJ2AxeWEAxWnW0EAHYU_BEwQFnoECBEQAQ&url=https%3A%2F%2Fsciencepress.mnhn.fr%2Fen%2Fperiodiques%2Fmycologie%2F26%2F3%2Ftaxinomie-ecologie-et-chorologie-des-especes-francaises-des-genres-hypotrachyna-et-parmelinopsis-ascomycota-lichenises-parmeliaceae&usg=AOvVaw3xRhQyiIv9hMK6tqTyiaOh&opi=89978449. This indicated that our find matched Hypotrachyna lividescens very well. This made sense as it was recorded further north that the other new Hypotrachyna species. It had already been found as far north as Brittany, so only a short hope over the channel.

The ecology is discussed further in this paper https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwju7uzdxuWEAxXVQEEAHYBBB18QFnoECBIQAQ&url=https%3A%2F%2Fsciencepress.mnhn.fr%2Fsites%2Fdefault%2Ffiles%2Farticles%2Fpdf%2Fcryptogamie-mycologie2004v25f3a6.pdf&usg=AOvVaw3Y3_lDKOjc2TCCY21gDEOj&opi=89978449” class=”bbcode_url”>https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwju7uzdxuWEAxXVQEEAHYBBB18QFnoECBIQAQ&url=https%3A%2F%2Fsciencepress.mnhn.fr%2Fsites%2Fdefault%2Ffiles%2Farticles%2Fpdf%2Fcryptogamie-mycologie2004v25f3a6.pdf&usg=AOvVaw3Y3_lDKOjc2TCCY21gDEOj&opi=89978449. The situation of a humid sheltered habitat on open trees matches that described for France, although it is typically more of a twig species, while we saw it on both a twig and on a trunk.

In email discussions it was suggested that we needed to TLC this to be sure, so I have sat on this for a bit but the alternatives are also new to Britain and less likely. Now, however, John Douglas and April Windle have found more in a park in Cornwall, so I am putting this out. The taxa should be looked for in similar habitat, sheltered trees and bushes in humid locations, elsewhere along the south coast. It might be doing a Teloschistes chrysophthalmus style invasion.

Good hunting

Neil