| TAXON: | Rusavskia elegans (Link) S.Y. Kondr. & Kärnefelt (2003) |
| RECENT SYNONYMS: | Xanthoria elegans (Link) Th. Fr. (1861) |
| FAMILY: | Teloschistaceae |
| GROWTH FORM: | Foliose, heteromerous |
| SUBSTRATES: | Nutrient-enriched calcareous and siliceous rock, and hard artificial substrates such as concrete, cement, etc |
| PHOTOBIONT: | Trebouxioid alga |
| REPRODUCTION: | Apothecia, pycnidia |
| ASCUS: | Clavate; apex Teloschistes-type; 8 spores |
| SPORES: | Ascospores ellipsoidal or ovoid, polarilocular, (9-)11-16 × 5-7(-9) µm; conidia ellipsoidal |
| NOTABLE FEATURES: | Thallus deep orange, often orbicular; lobes narrow, convex, adpressed, discrete, finger-like; attached to substrate by hapters not rhizines; apothecia abundant, crowded, lecanorine; discs orange |
| CHEMICAL TESTS: | Thallus K+ crimson-purple, UV+ red (parietin, minor amounts of other anthraquinones) |
| HABITAT: | Well-lit situations wherever suitable substrate available; associated with bird-perches; nitrophilic |
| DISTRIBUTION: | Locally common in Britain |
| CONSERVATION STATUS: | Least Concern |
| LICHENICOLOUS FUNGI: | – |
| IDENTIFICATION DIFFICULTY: | Green 1: Field identification possible |
| CONFUSION SPECIES: | Calogaya pusilla |
FIELD NOTES
Rusavskia elegans is one of the most straightforward British lichens to identify, with its deep orange colour, sausage-like or finger-like lobes, and abundant apothecia. Now known to be the only member of the Rusavskia genus in Britain, it was until recently considered a Xanthoria. But it closely resembles none of the species still classified as Xanthoria, nor indeed any other British lichen.
Even so, it might be possible for the unwary to confuse R. elegans with Calogaya pusilla, which also forms small, orbicular, lobate thalli on calcareous substrates. Normally more yellow in colour, and often white towards the centre, C. pusilla can sometimes display an even orange tone. Like R. elegans and many other lichens in the Teloschistaceae family, it also tests K+ red-purple due to parietin.
Nevertheless, a moment’s inspection should convince you which of these species you’ve encountered. Even when it’s more orange, C. pusilla forms ‘tighter’ thalli, with shorter lobes pressed more firmly against one another. It also tends to be somewhat pruinose on both lobes and apothecia.
By contrast, R. elegans forms ‘looser’ thalli. Its longer and more distinct lobes appear independently to probe the uncolonised substrate beyond the thallus margin. It also lacks any pruina.
As they become overmature, R. elegans thalli sometimes disintegrate into patchy clumps of lobes. In this state, the resemblance to C. pusilla might be stronger. But it would still be superficial: even if none of the distinguishing features above are clear, R. elegans is a foliose lichen with a white lower cortex, while C. pusilla is a crustose lichen with no lower cortex at all.
Like Physcia caesia recently posted, R. elegans is found on every continent, and from the Arctic to the Antarctic. But it makes one extraordinary claim to even greater fame. It was once put into orbit on the International Space Station, set outside, and fully exposed to the vacuum, radiation and extreme conditions of space for eighteen months. It survived, and upon returning to Earth, it gamely resumed photosynthesis.
LAB NOTES
Rusavskia elegans can normally be identified without microscopy.
SPECIMENS
Rusavskia elegans : England : VC28 West Norfolk : TF9528 : October 2024 : On concrete bridge parapet
