SPECIMEN EXAMINED. — Antarctica. West Antarctic Peninsula, Graham Coast, Grandidier Channel, Lahille Island at the north-eastern entrance of Leroux Bay west of Barison Peninsula, 65°33’12.89”S, 64°23’42.14”W, on ground in the bryophyte carpet and mat subformation, 7.II.2020, Parnikoza 6B/20 (KRAM[B-259591]).
Polytrichum juniperinum was found on Lahille Island on a unique vegetated point on the island’s south-western coast in the bryophyte carpet and mat subformation, with patches of the grass Deschampsia antarctica É.Desv. (Poaceae) and cushion-forming Colobanthus quitensis (Kunth) Bartl. (Caryophylaceae), the only two vascular plants that are native to the Antarctic. Like elsewhere in Antarctica, it is a pioneer species growing on soil and humus and colonising communities of the fruticose lichen and moss cushion subformation, often in association with vascular plants (Ochyra et al. 2008a). In this locality it is associated with Brachythecium austroglareosum (Müll. Hal.) Kindb. and Pohlia drummondii (Müll.Hal.) A.L.Andrews.
The present new locality of Polytrichum juniperinum on Lahille Island is the southernmost discovery of this species on the Graham Coast. The species was previously known in this region only from Uruguay Island in the Argentine Islands, Cape Tuxen on the mainland Graham Coast and Darboux Island in Collins Bay (Ochyra et al. 2008a). Thus, the discovery of this species on Lahille Island shifts the southern limit of its occurrence in the Graham Coast area about 16 km to the south (Fig. 2). In general, P. juniperinum reaches its southernmost locality in the Antarctic at latitude 67°58’S on Camp Point in Marguerite Bay on the Fallières Coast.