Stereocaulon botryosum Acharius (1810: 581)

Oset, Magdalena & Kukwa, Martin, 2014, Typification of two Stereocaulon names (Lecanorales, Ascomycota), Phytotaxa 181 (3), pp. 188-191 : 188-189

Stereocaulon botryosum Acharius (1810: 581)

Type: —[ Switzerland] ‘ Helvetia’ , [Schleicher] 930 ([first-step] lectotype H-ACH 1768!, designated by Lamb [1977: 207]; [second-step] lectotype H-ACH 1768A!, designated here; isolectotype BM-ACH 773!, left-hand specimen) .

Chemistry: As stated by Lamb (1977) the species contains atranorin and porphyrilic acid and these substances are present in the original material.

Comments: Stereocaulon botryosum is characterized by evanescent primary thallus, 1.5 – 2.5 cm tall, branched from the base pseudopodetia, which become fastigiate and cauliflower-like at the tips, glaucous or whitish-grey, grainlike, verrucose or subsquamulose phyllocladia, dark brown cephalodia containing Nostoc , apothecia formed at the end of phyllocladia and the production of atranorin and porphyrilic acid ( Lamb 1951, 1977).

Stereocaulon botryosum was introduced by Acharius (1810). The main part of his lichen collection is stored at the University of Helsinki, where we found one herbarium sheet (H-ACH 1768) annotated by Acharius as S. botryosum ( Figure 1 ). It consists of four specimens with the note ‘Helvetia’, which corresponds to the information included in the protologue: ‘Habitat ad montes Helvetiae. Schleicher’ ( Acharius 1810). The collection is, however, heterogeneous and only one specimen (as H-ACH 1768A) represents S. botryosum as currently understood. The other specimens are Cladonia parasitica (Hoffmann) Hoffmann (1796: 127) (H-ACH 1768B) and Stereocaulon alpinum Laurer in Funck (1827: 6) (H-ACH 1768C and 1768D; both specimens contain atranorin and lobaric acid).

The entire gathering in H-ACH was cited by Lamb (1977) as the lectotype, but he did not refer to any of these specimens more directly. There is no Lamb’s annotation label attached to this collection and we suspect that he did not examine it by himself, but possibly saw only the photograph of Stereocaulon botryosum cited in Frey (1933) as ‘Original im Herb. Acharius’. The heterogeneity of the collection was also briefly discussed by Frey (1933), but Lamb (1977) did not refer to repeat that information. Nevertheless, the designation of H-Ach 1768 as lectotype by Lamb (1977) must be accepted. However, as the gathering consists of more than one specimen and moreover it is heterogeneous, the subsequent second-step lectotypification is proposed here in accordance with Art. 9.17 of ICN (McNeill et al. 2012), and the specimen H-ACH 1768A is here selected as the definite lectotype.

The collection in BM-ACH also includes original material of this species. The gathering BM-ACH 773 consists of three specimens with the note: ‘ Stereocaulon botryosum . Achar. Lichenogr. Univers.’, but no additional details are provided. Only one of them (left-hand specimen) belongs to S. botryosum . The specimen is morphologically very similar and seems to be part of the material deposited in H-Ach; it is here considered an isolectotype.

Selected exsiccatae examined. Arnold, Lich. Exs. 1575 (H, sub S. alpinum ). Hansen, Lich. Groenl. Exs. 208 (B–46358), 440 (B–90838, BM), 632 (B–116761), 792 (B–130962). Malme, Lich. Suec. Exs. 979 (B–158701, sub S. fastigiatum var. dissolutum ), 979A (H, sub S. fastigiatum ). Petrak, Crypt. Exs. Vindob. 3664 (H, sub S. fastigiatum var. dissolutum ).

Figures

FIGURE 1. Type collection of Stereocaulon botryosum in H-ACH. A, lectotype of S. botryosum. B, Cladonia parasitica. C & D, Stereocaulon alpinum. Denotation of specimens following the rules used for the collection in H- ACH. © Botanical Museum (H), FMNH, University of Helsinki.