Atla (lichen)


Atla is a genus of crustose lichens in the family Verrucariaceae. It has nine species that grow on rocks or on soil.

Taxonomy

The genus was circumscribed in 2008 by Sanja Savić and Leif Tibell, with Atla alpina assigned as the type species. According to the authors, the generic name Atla refers to "the name of a Norse water goddess who sometimes accompanied us in the same habitats as the species named after her." Three species were included in the original circumscription of the genus; these species formed a well-defined clade in the family Verrucariaceae, sister to a clade containing several Sporodictyon species. Several newly described species were later added from Alaska and Finland.

Description

Atla lichens have crustose thalli that are blackish in colour with a surface texture ranging from warty to diffusely areolate to immersed in the substrate. The perithecia are 0.3–0.9 mm in diameter, and either sessile or immersed. Ascospores are ellipsoid, hyaline to dark brown when mature, and measure 43–87 by 19–49 μm; the spores are muriform, with 7–15 transverse and 2–5 longitudinal walls. The excipulum is spherical, ranging in colour from black to dark brown. The involucrellum is well developed; depending on the species, the upper part of this structure is either fused together with the excipulum, or missing altogether.

Species