Orcularia, 2011

Kalb, Klaus & Giralt, Mireia, 2011, Orcularia, a segregate from the lichen genera Buellia and Rinodina (Lecanoromycetes, Caliciaceae), Phytotaxa 38, pp. 53-60 : 54-56

ORCULARIA (Malme) Kalb & Giralt , gen. et stat. nov. Mycobank MB 563558

Rinodina (Ach.) Stiz. Sect. Orcularia Malme, Bihang till Konglige Svenska vetenskaps-akademiens handlingar 28, 3(1): 44 (1902). Typus generis:— Orcularia insperata (Nyl.) Kalb & Giralt

Thallus whitish, grey or evanescent. Apothecia initially erumpent and apparently lecanorine, initially surrounded by thalline tissue simulating a thalline exciple, becoming sessile and with a thin proper margin with age, small. Proper exciple poorly developed, prosoplectenchymatous, inner cells elongate, hyaline to pale brown, outermost cells short, brown, swollen like the apical caps of the paraphyses. Hypothecium brown, not deep. Hymenium not inspersed. Paraphyses with a distinct but moderately swollen dark brown cap, (2–) 3– 5 µm diam. Ascospores Orcularia- type, bilocular with long lumina canals (isthmus), or tetralocular with one additional lumen in each canal, pale brown with paler apices, ± citriform with mucronate apices, walls smooth, torus absent; ontogeny Orcularia- type (the septum is inserted after lateral wall thickenings become distinct). Conidia filiform. Ascus Bacidia- type. Photobiont a coccoid green alga. Chemistry: no secondary lichen products, xanthones, myeloconone D1 or norstictic acid.

Notes:— Malme (1902) introduced the name Orcularia as a section of Rinodina with R. insperata (Nyl.) Malme as the only Brazilian species. He distinguished section Orcularia from other sections of Rinodina by spore characters and the brown hypothecium. Sheard (1967) followed this scheme and included an additional species, Rinodina biloculata (Nyl.) Sheard , in the section Orcularia .

The genus Orcularia shares some characters with Amandinea Choisy ex Scheidegger & H. Mayrhofer , namely the filiform conidia and apothecia with an initial pseudothalline margin, and Marbach (2000) actually transferred these species to Amandinea . However, the Orcularia- type ascospores and their ontogeny are very different from those occurring in Amandinea and unique within the Physciaceae (and Caliciaceae ), so that their placement in an independent genus seems more appropriate. Species belonging to Amandinea have Buellia- type ascospores (without any inner wall thickening) or Physconia- type ascospores (with inner wall thickenings ± pronounced only at the septum and also occasionally at the apices, although these are rather weak and are only observed briefly during the ascospore development). Physconia- type ascospores with a very thick septum and long and narrow lumina canals (= polarilocular) have often been called Orcularia - type (e.g. in Mayrhofer 1984). However, in the strict sense, Orcularia - type ascospores follow a different ontogeny than the Physconia- type and, at present, have only been observed in the taxa included in this contribution. In ascospores with Physconia- type ontogeny, the septum is inserted before any inner wall thickening appears whereas in Orcularia - type ascospores, the septum is inserted after lateral inner wall thickenings become distinct. Consequently, immature non-septate ascospores with pronounced lateral thickenings (with a single lumen ± bone-shaped) are common and very characteristic in the Orcularia- type ( Fig. 1 ) but totally absent in the Physconia- type. Further the ascospore walls in Amandinea are often microrugulate or rugulate and become dark brown whereas in Orcularia they are always smooth and pale brown. The ± citriform shape of Orcularia ascospores with mucronate apices is also very characteristic.

Another genus with filiform conidia and polariloculate ascospores is Fluctua Marbach. But this genus differs in having pruinose apothecia with a distinct, thick, prominent and flexuous excipulum (somewhat lirelliform in appearance) which contains norstictic acid, a thallus containing norstictic acid, hardly thickened endcells of the paraphyses, and immature non-septate ascospores with subapical inner wall thickenings (Callispora - type ontogeny) and mature ascospores with subapical and septal inner wall thickenings (see Marbach 2000, Abb. 96: 211). In fact, Fluctua seems to be more closely related to Buellia s. str. (= Hafellia ) from which it differs by the absence of hymenial oil droplets and the presence of filiform conidia.

Figures

FIGURE 1. Spore ontogeny of Orcularia species. A. O. insperata. B. O. elixii. C. O. placodiomorpha. D. O. placodiomorphoides. Scale: 10 µm.