Dimelaena subsquamulosa Giralt, H. Mayrhofer, van den Boom & Elix, 2014

Dimelaena subsquamulosa Giralt, H. Mayrhofer, van den Boom & Elix sp. nov.

( Fig. 3 View FIGURE 3 ) MycoBank MB 807085

Thallus saxicolous, composed of subsquamulose areoles, discrete to continuous, loosely attached to substrate, pale orangebrown. Apothecia lecanorine, mostly subimmersed, 0.3–0.5(–0.8) mm diam. Hymenium not inspersed with oil droplets. Hypothecium hyaline. Ascospores Buellia- type, (12.0–)13.9–17.0(–19.0) × (6.0–)7.2–8.7(–10.0) µm, ellipsoid with nonornamented walls. Conidia bacilliform, 3.0–5.0 × 1.0 µm. Chemistry. Chemotype I: without secondary metabolites (holotype and isotype specimens); chemotype II: gyrophoric acid in the cortex (paratype, hb. v.d. Boom 33043).

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, 2500m, 14º47.1’N, 91º32.9’W, 23 July 2004, P. & B. van den Boom 32928 (holotype GZU! GoogleMaps , isotype hb. v.d. Boom! GoogleMaps ).

Thallus thick, areolate, margin not lobate. Areoles subsquamulose, 0.3–1.5(–3.0) mm wide, scattered or usually continuous, regularly rounded to sublobate or elongated, plane to slightly subconvex, loosely attached to substrate mainly by the central part with slightly ascending margins, creamy to pale orange-brown, margins often covered by a whitish pruina. Upper cortex 30–60 µm thick, composed of small isodiametric cells, 2.0– 3.5 µm in diam., colourless except the uppermost cells which are pigmented orange-brown. Epinecral layer 5–10(–15) µm thick. Algal layer 50–90 µm thick with large trebouxioid algal cells, 10–15(–18) µm diam. Medulla with upper part below algal layer, hyaline, lower part ±imbedded in reddish-brown substrate, not amyloid, I-. Lower cortex absent. Prothallus absent. Apothecia lecanorine, 0.3–0.5(–0.8) mm diam., immersed, subimmersed to adnate. Thalline margin concolorous or darker than thallus, usually persistent. Disc flat, epruinose, dark reddish brown. Thalline exciple 30–50 µm thick, composed of small isodiametric cells 2–3 µm diam., like the thalline cortex. Epihymenium orange-brown, N-. Hymenium hyaline, not inspersed with oil droplets, 50–70(–100) µm high. Hypothecium hyaline, 80–100 µm deep. Asci Bacidia - type, 8-spored. Apical cells of paraphyses weakly enlarged, 2.0–3.0 µm in diam., colourless or with pale brown caps. Ascospores Buellia - type, (12.0–)13.9–17.0(–19.0) × (6.0–)7.2–8.7(–10.0) µm (M= 15.4 × 7.9 µm; SD= 1.5 × 0.8 µm; n= 111), ellipsoid, straight or sometimes slightly curved, constricted at septum; walls not ornamented. Conidia bacilliform, 3.0–5.0 × 1.0 µm.

Chemistry: ―Chemotype I: all spot tests negative; no lichen substances detected by TLC; chemotype II: C+ rose; gyrophoric acid by TLC.

Etymology: ―The epithet refers to the subsquamulose thallus of this species.

Ecology and distribution: ―The two known collections were found in mountainous areas between 2500 and 3150 m elevation. Both areas have been influenced by human activity. In the type locality this species was growing on top of a volcanic outcrop in an open area along a trail, and was associated with Buellia rugosissima and close to several brownish and yellowish Acarospora species. The accompanying macrolichens were the same as mentioned under B. rugosissima . In the second locality, situated on the same mountain slope but at 3150 m elevation, crustose lichens growing nearby included Buellia aethalea , B. eganii Bungartz , Candelariella rosulans (Müll. Arg.) Zahlbr. and Trapelia coarctata (Sm. & Sow.) M. Choisy. Accompanying macrolichens included Physcia dubia (Hoffm.) Lettau , Punctelia borreri (Sm.) Krog. , Stereocaulon pachycephalum Vain. , Umbilicaria leprosa (Zahlbr.) Frey and Xanthoparmelia cumberlandia (Gyeln.) Hale. The latter taxa were reported in van den Boom et al. (2007).

Notes: ― Dimelaena subsquamulosa is characterized by the creamy to pale orange-brown thallus composed of thick, subsquamulose areoles, the lecanorine apothecia, the hyaline hypothecium, the Buellia - type ascospores and the bacilliform conidia. Among the Physciaceae with a crustose thalli or thalli of an intermediate growth form (i.e. placodioid, subsquamulose to squamulose), only the genus Phaeorrhiza H. Mayrhofer & Poelt and some species of Dimelaena Norman show the same combination of diagnostic characters than D. subsquamulosa .

The thalline and apothecial characters of this new species are macro- and microscopically very close to Phaeorrhiza nimbosa (Fr.) H. Mayrhofer & Poelt but it differs in having much smaller squamules, apothecia and ascospores. However, the inclusion of D. subsquamulosa in Phaeorrhiza does not seem appropriate since it lacks the typical brown rhizoidal hyphae, the main diagnostic character of this genus ( Mayrhofer & Poelt 1978). Further, the ascus of Phaeorrhiza is of the Lecanora- rather than Bacidia - type ( Rambold et al. 1994).

As a consequence, the new species is better included in the genus Dimelaena . Although this genus is generally characterized by placodioid thalli which are areolate in the center and have radiate-plicate marginal lobes, it includes two species, D. californica (H. Magn.) Sheard and D. lichenicola K. Knudsen, Sheard, Kokourcová & H. Mayrhofer which, probably do to their lichenicolous behaviour, show reduced thalli lacking well-developed plicate margins ( Knudsen et al. 2013). Furthermore, the genus Dimelaena exhibits variable apothecial characters, as it includes species with lecanorine or lecideine apothecia and with hyaline or brown hypothecia. Among the ten species currently included in Dimelaena , D. australiensis H. Mayrhofer & Sheard , D. oreina (Ach.) Norman , D. tenuis (Müll. Arg.) H. Mayrhofer & Wippel , D. thysanota (Tuck.) Hale & W.L. Culb. and D. weberi Sheard have a colourless hypothecium. The new species clearly differs from all of these taxa in having much larger ascospores. Concerning the chemistry, among the Dimelaena taxa mentioned above, only D. tenuis and D. thysanota as D. subsquamulosa also contain gyrophoric acid, however in D. tenuis this secondary metabolite is usually accompanied or substituted by 5- O -methylhiascic acid ( Elix 2011) and in D. thysanota by sphaerophorin and subsphaeric acid ( Mayrhofer & Sheard 2004).

An additional genus of Physciaceae with subsquamulose thallus is Monerolechia (Fr.) Kalb , recently resurrected by Kalb (2004) but not yet fully accepted. However, this monotypic genus clearly differs from D. subsquamulosa by having lecideine apothecia, a brown hypothecium and Physcia tenella- type asci (= Lecanoratype) (cf. Marbach 2000, abb 10: 28 and Kalb 2004).

Additional specimens examined: ― 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, 2500m, 14º47.1’N, 91º32.9’W, 23 July 2004, P. & B. van den Boom 32921, 32941 (paratypes, hb. v.d. Boom); GoogleMaps (A) NW of Quezaltenango, NNW of San Marcos, along trail from San Sebastian to top of volcano Tajumulco , on ENE slope, above the small village El Rodeo, shrubs and outcrops in open field, 3150 m, 15° 2.9' N, 91° 51.3' W, 25 July 2004, P. & B. van den Boom 33043 (paratype, hb. v.d. Boom) GoogleMaps .