| TAXON: | Lecanora gangaleoides Nyl. (1872) |
| RECENT SYNONYMS: | – |
| FAMILY: | Lecanoraceae |
| GROWTH FORM: | Crustose, heteromerous |
| SUBSTRATES: | Siliceous rock |
| PHOTOBIONT: | Trebouxia alga |
| REPRODUCTION: | Apothecia, pyncidia |
| ASCUS: | Cylindrical; apex Lecanora-type; 8 spores |
| SPORES: | Ascospores ellipsoid to subglobose, aseptate, (10-)12-15(-18) × (5-)6-8(-9) µm; conidia filamentous |
| NOTABLE FEATURES: | Thallus grey, irregularly areolate, warty, crumbly; apothecia lecanorine; discs black; deep medulla orange |
| CHEMICAL TESTS: | Thallus K+ yellow, Pd± yellow-orange or red, UV± pale orange, K/UV+ yellow (atranorin, chloratranorin, gangaleoidin); deep medulla K+ purple (skyrin) |
| HABITAT: | Natural or worked stone, especially but not exclusively on rocky shores in xeric-supralittoral zone (upper splash zone or ‘grey zone’); rarely on worked timber |
| DISTRIBUTION: | Widespread and common on rocky shores; locally abundant inland; infrequent in central and eastern England |
| CONSERVATION STATUS: | Least Concern |
| LICHENICOLOUS FUNGI: | Epithamnolia xanthoriae, Muellerella pygmaea, Stigmidium sp., Taeniolella inc. |
| IDENTIFICATION DIFFICULTY: | Green 2: Field identification possible with care |
| CONFUSION SPECIES: | Tephromela atra |
FIELD NOTES
Lecanora gangaleoides is a common and distinctive saxicolous lichen, found especially but not exclusively at or near the coast. Its grey, rough, crumbly thallus, often overgrown with jumbled-up black apothecia, is recognisable more or less on sight. Were it not for its resemblance with the even more common Tephromela atra, which is found in very similar habitat, it would be one of the easier British lichens to identify.
Happily, it only takes a moment to distinguish the two species. There are three reliable differences:
- The interior of an apothecium of L. gangaleoides is pale green, whereas that of T. is purple-brown
- The deep medulla of L. gangaleoides is orange, whereas that of T. atra is not
- The deep medulla of L. gangaleoides reacts K+ purple, whereas that of T. atra doesn’t
If you believe you’ve encountered L. gangaleoides, simply section an apothecium in the field with a razor-blade or very sharp knife, and observe the colour of the interior. If you’re still unsure, scratch a bit of the crumbly thallus away, and check for an orange colour where it meets the substrate. And if for whatever unusual reason you’re still unsure, test the orange medulla with K, and look for a K+ purple reaction as the potassium hydroxide reacts with skyrin, the anthraquinone that lends the medulla its orange pigmentation.
All three of those points of distinction are illustrated below. Once you become familiar with both L. gangaleiodes and T. atra, you’ll anticipate one result or the other. The two lichens look different to the practised eye: L. gangleoides with a greyer thallus and more uniformly smaller apothecia, and T. atra with a whiter thallus and apothecia of more varied sizes, including quite large ones.
LAB NOTES
Lecanora gangaleoides can normally be identified without microscopy.
SPECIMENS
Lecanora gangaleoides : England : VC70 Cumberland : NY5764 : August 2024 : On siliceous drystone wall : First hectad record
Lecanora gangaleoides : Scotland : VC101 Kintyre : NR6974 : August 2024 : On siliceous outcrop
Lecanora gangaleoides : Scotland : VC101 Kintyre : NR7785 : August 2024 : On siliceous gravestone
Lecanora gangaleoides : Scotland : VC98 Argyll : NR8688 : July 2022 & August 2024 : On sandstone gravestone
