Seawardiella

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Seawardiella is a small genus of lichen-forming fungi in the family Teloschistaceae. It contains two bark-dwelling crustose lichens: Seawardiella lobulata and Seawardiella tasmaniensis. The genus was defined in 2018 by lichenologists Sergey Kondratyuk, Ingvar Kärnefelt, and Arne Thell and is named in honor of British lichenologist Mark Seaward. Seawardiella belongs to the subfamily Xanthorioideae.

The genus is similar to Calogaya but can be told apart by its underdeveloped thalline (surface) tissue and the absence of vegetative reproductive structures. In 2021, some classifications did not recognize Seawardiella as a separate genus and grouped it with Calogaya.

Form and habitat:
- Seawardiella lichens grow on tree bark (corticolous) and range from small rosette-like forms to less defined lobules near the fruiting bodies.
- They are pale whitish-grey to yellow-grey, sometimes yellow.
- Apothecia are numerous, often with a stalk-like thalline structure; the disc is flat to slightly convex.
- The outer and inner layers around the spores are made of closely interwoven cells (paraplectenchymatous).

Reproduction and chemistry:
- Each ascus contains eight spores.
- Spores are clear (hyaline) and two-celled (bipolarilocular).
- The K spot test (potassium hydroxide) typically yields a purple reaction, including on the epihymenium and the true exciple.

Distribution:
- Seawardiella lobulata is widely distributed in the Northern Hemisphere.
- Seawardiella tasmaniensis is known from the Southern Hemisphere but is less well documented.

Species:
- Seawardiella lobulata
- Seawardiella tasmaniensis