Astrochapsa elongata

Astrochapsa elongata is a little-known species of corticolous (bark-dwelling), crustose lichen in the family Graphidaceae. Found only in a specific region of Thailand, it is closely related to Astrochapsa recurva, yet distinguishes itself through its narrower and absence of secondary metabolites.

Taxonomy
Astrochapsa elongata was described as a new species in 2019 by lichenologists Vasun Poengsungnoen and H. Thorsten Lumbsch. The type specimen was collected at Khok Nok Kraba ranger station in Thailand's Phu Luang Wildlife Sanctuary, on the bark of Rhododendron simsii in low-mountain scrubland. The specific epithet elongata refers to the elongated ascomata found in this species.

Description
Astrochapsa elongata features a corticolous thallus that can grow up to 5 cm in diameter and 30–60 μm thick. Its surface is smooth to uneven, cracked, whitish-grey, and slightly glossy. The associated with this lichen is Trentepohlia, and a medulla is absent. Apothecia are, angular-rounded to mostly elongate, measuring 3.0–7.0 by 1.5–3.0 mm, and can be or sometimes branched. The is partly to completely exposed and covered by thick white. are with 15–25 transverse septa and 0–1 longitudinal septum per segment, measuring 40–65 by 10–13 μm. No pycnidia have been observed.

Astrochapsa elongata is very similar to Astrochapsa recurva, but it can be differentiated by its narrower ascospores and the absence of secondary metabolites. Other similar species include Astrochapsa zahlbruckneri, Chapsa cinchonarum, and Pseudochapsa dilatata, which can be distinguished by their ascospore characteristics.

Habitat and distribution
Astrochapsa elongata has been found on the trunk of Rhododendron simsii in northeastern Thailand, specifically in the lower montane scrub. At the time of publication, it was only known to occur at its type locality.