Flora of New Zealand Series

Type : Cetraria islandica (L.) Ach. [=Lichen islandicus L.]

Description : Thallus fruticose dark-brown to paler brown, occasionally reddish at base. Lobes ±canaliculate, almost subtubular or ±terete, occasionally becoming markedly expanded towards apices, occasionally also markedly faveolate or wrinkled, pseudocyphellate. Pseudocyphellae marginal or laminal on lower surface. Margins with scattered, branched or unbranched cilia. Cortex composed of an external layer of pachydermatous, paraplectenchymatous hyphae mostly overlaying a ±thin layer of periclinally arranged prosoplectenchymatous hyphae. Ascomata apothecia, marginal on upper surface. Hamathecium of paraphyses, usually straight, sparsely branched with swollen tips. Asci clavate to cylindrical, 30–55 × 7–13 μm, tholus moderately large, with an apical ring structure; ocular chamber conical with narrow beak; axial body small 0.8–1.6 μm. Ascospores ellipsoidal, 5–10 × 2.5– 5 μm. Conidiomata pycnidia, on marginal projections, wall two-layered, non-pigmented, outer layer thin, to 5 μm thick, with cortical tissue beneath. Conidia oblong-citriform.

The circumscription of Cetraria was reconsidered by Kärnefelt et al. (1993) who accept 16 species within it (Thell et al. 2004). The asci have a relatively small axial body within a rather large tholus, and a distinctive amyloid ring (lacking in both Cetrariella Kärnefelt & Thell, and Tuckermanopsis Gyeln.); this taxonomy being supported by the conidia being oblong and citriform in shape. It is placed in the family Parmeliaceae (Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005). Three species are recorded in New Zealand, occurring in high-alpine, tundra vegetation of South Island mountains E of the Main Divide. The taxon C. australiensis W.Weber ex Kärnef., which occurs in scattered alpine localities in New South Wales (Kärnefelt 1979; Kantvilas et al. 2002: 28), has not yet been recorded from New Zealand. In a recent molecular study of cetrarioid lichens (Mattsson & Articus 2004), the well-supported Cetraria -clade may be regarded as the central core.

Nineteenth century taxa described from New Zealand and recorded as species of Cetraria (Randlane et al. 1997) are now placed elsewhere. (1) Cetraria dermatoidea (Stirt.) Zahlbr. [=Platysma dermatoides Stirt. (Stirton 1873: 21)] is referable to Pannaria araneosa (q.v.); (2) Cetraria corallophora Müll.Arg. (Müller Argoviensis 1892: 26) is referable to Punctelia subflava (q.v.); (3) and Cetraria novae-zelandiae (C.Knight) Zahlbr. [=Platysma novae-zelandiae C. Knight (Knight 1876: 328)] remains to be determined, but it is not a species of Cetraria.