When Lindsay (Reference Lindsay1974) described Antarctomia subcoralloides from South Georgia, he noted the great habitual resemblance of the thallus to that of Arctomia. Henssen (Reference Henssen1981) reported the original collection to be a mixture of Placynthium asperellum (Ach.) Trevis., upon which she typified the name, the fruiting bodies of an associated pyrenocarpous fungus, and Pannaria (=Vahliella) leucophaea (Vahl) P. M. Jørg., which was the source of Lindsay's record of Nostoc as the photobiont. A recent re-examination by the author of the type (in AAS) confirms this interpretation, but the latter proved to be Protopannaria austro-orcadensis (Øvstedal) P. M. Jørg. (a species not described until 1993) and not Vahliella leucophaea, which is otherwise not recorded from the Southern Hemisphere (Jørgensen Reference Jørgensen1978). Henssen (op. cit.) also reported Arctomia delicatula Th. Fr. from Patagonia (Lago Argentino, Henssen & Vobis 24515i), but it has not been possible to trace this specimen. This is unfortunate since it is likely to be correct and would be the first record of the genus from the Southern Hemisphere. Arctomia subantarctica Øvstedal from Kerguelen (Øvstedal & Gremmen Reference Øvstedal and Gremmen2001) does, as previously pointed out (Jørgensen Reference Jørgensen2003), not belong in the genus. There are accordingly no verifiable records of this genus in the Southern Hemisphere.

However, among collections recently sent to me by Dr William R. Buck (NY) from a collecting trip in the southernmost part of South America, I found a very well-developed specimen of Arctomia delicatula (Fig. 1). This is a most interesting addition to the lichen biota in this part of the world. The species was described from northern Norway and has a wide distribution in the Northern Hemisphere (Lynge Reference Lynge1926). It is thus an addition to that much discussed bipolar element in the lichen biota (e.g. Galloway Reference Galloway2008, with numerous examples). In this case there are, unlike for example Pannaria hookeri (Sm.) Nyl. (Jørgensen Reference Jørgensen1978; Jørgensen & Palice Reference Jørgensen and Palice2010), no records from intermediate high mountains in Africa or South America. There is, however, an additional species of the genus in the Himalayas, Arctomia teretiusculum P. M. Jørg. (Jørgensen Reference Jørgensen2003).

Fig. 1.

Arctomia delicatula, part of the collection from Cape Horn (NY). Scale=1 mm.

Photograph: Jan Berge.

The material from Cape Horn exhibits the typical characters of the species (Henssen Reference Henssen1969), having a loosely organized, granular-squamulose thallus with a single, cellular cortical layer and long, fusiform ascospores, 60–80×4–5 µm. This material grew over a cushion of Ulota sp. on a Berberis bush in a Magellanic tundra on a rocky slope with small waterfalls. This is consistent with its ecology in the Northern Hemisphere, where it is bryophilous in tundras or on bushes and small trees (Jørgensen Reference Jørgensen, Jørgensen, Tønsberg and Vitikainen2007).

Specimen studied. Chile: Antarctica Chilena: Comuna Cabo de Hornos, Isla Grande, Parque Nacional Alberto Agostino, Peninsula Edward in sounds between Punta Abrigo and Cabo Saliente, Puerto Langlois, 2009 W. R. Buck 57395 (NY).