Buellia rugosissima Giralt, van den Boom & Elix, 2014

Buellia rugosissima Giralt, van den Boom & Elix sp. nov. ( Fig. 2 View FIGURE 2 ) MycoBank MB 807079

Thallus saxicolous, rimose-areolate, pale greyish-brown, containing atranorin. Prothallus present, dendritic, black. Medulla not amyloid, I-. Apothecia lecideine, remaining immersed, 0.1–0.4 mm diam. Proper exciple poorly differentiated, aethaleatype, brown-aeruginose like the epihymenium, N+ red-violet. Hymenium without oil droplets. Hypothecium hyaline. Ascospores Buellia - type, (15.0–)16.1–19.7(–21.0) × (8.0–)8.4–10.4(–11.5) µm; walls strongly rugulate (ornamentation visible at × 400). Conidia bacilliform, 5.0–6.0 × 1.0 µm.

Type:― GUATEMALA. (A) Quezaltenango: S of Quezaltenango, S of Llano del Pinal, N slope of Volcano Santa María , path among small agriculture fields with small forests, shrubs, trees and outcrops, 2500 m, 14º47.1’N, 91º32.9’W, 23 July 2004, P. & B. van den Boom 32921 (holotype GZU! GoogleMaps , isotype hb. v.d. Boom! GoogleMaps ).

Thallus saxicolous, crustose, thin, ±continuous, epilithic, becoming rimose-areolate to areolate, matt, whitish-grey to pale greyish-brown to brownish. Medulla not amyloid, I-. Prothallus distinct, dendritic, also visible between the areoles, black. Photobiont trebouxioid; algal cells 7–15 µm diam. Apothecia lecideine, (0.1–)0.2–0.3(–0.4) mm diam., remaining immersed, predominantly in center of areoles. Proper margin usually indistinct, very rarely visible, black. Disc epruinose, plane, black. Proper exciple aethalea- type, poorly differentiated, outer part brownaeruginose, 20–40 µm thick, N+ red-violet; inner part indistinct, colourless, up to 10 µm thick. Epihymenium brown-aeruginose, N+ red-violet. Hymenium hyaline, not inspersed with oil droplets, 80–100 µm high. Hypothecium hyaline, 40–80 µm deep. Asci Bacidia - type, 8-spored. Apical cells of paraphyses 2.0– 3.5 µm wide, brown capitate. Ascospores Buellia - type, of (15.0–)16.1–19.7(–21.0) × (8.0–)8.4–10.4(–11.5) µm (M= 17.9 × 9.4 µm; SD= 1.8 × 1 µm; n= 28), broadly ellipsoid, strongly rugulate (ornamentation visible at × 400), constricted at septum when mature. Conidia bacilliform, 5.0–6.0 × 1.0 µm.

Chemistry: ―Thallus K+ yellow; atranorin detected by TLC.

Etymology: ―The epithet refers to the strongly rugulate walls of the ascospores.

Ecology and distribution: ―The known collections were found in a mountainous area at 2500 m elevation. The area has been influenced by human activity. At the type locality this species grows together with Dimelaena subsquamulosa , on a sloping, southerly exposed outcrop. Crustose lichens growing nearby included several brown Acarospora species , one of which has a C+ red thallus and could refer to A. fuscata (Nyl.) Arnold and several yellow Acarospora specimens which have not yet been identified. Lepraria vouauxii (Hue) R.C. Harris was collected from the vertical surface of the outcrop. Accompanying macrolichens on the same outcrop included Physcia tribacia (Ach.) Nyl. , Xanthoparmelia conspersa (Ach.) Hale and X. cumberlandia (Gyeln.) Hale. The latter four species were reported in van den Boom et al. (2007).

Notes: ― Buellia rugosissima is characterized by the rimose-areolate, greyish-brown thallus containing atranorin, the non-amyloid medulla and a very well delimited dendritic, black prothallus, the small, persistently immersed apothecia, the brown-aeruginose epihymenium (N+ red-violet), the hyaline hypothecium and the large Buellia - type ascospores with a strongly rugulate ornamentation. These characters indicate that this new species belongs to the B. aethalea- group. However, it is clearly distinguished from other members of this group ( B. aethalea (Ach.) Th. Fr. , B. spuria (Schaer.) Anzi and B. stellulata (Taylor) Mudd ) by its chemistry and larger and strongly ornamented ascospores (cf. Bungartz & Nash 2004). Buellia cranfieldii Elix from Australia has identical chemistry and similar apothecial anatomy, but the ascospores are much smaller (10–16 × 5–8 µm) and have nonornamented walls ( Elix 2010).

Additional specimens examined: ― GUATEMALA. (A) Quezaltenango: S of Quezaltenango, S of Llano del Pinal, N slope of volcano Santa Maria , path among small agriculture fields with small forests, shrubs, trees and outcrops along path, on outcrop, 2500m, 14° 47.1' N, 91° 32.9' W, 23 July 2004, P. & B. van den Boom 32928, 32935 (paratypes hb. v.d. Boom) GoogleMaps .