Cladonia cayennensis Ahti & Sipman, 2013

Ahti, Teuvo & Sipman, Harrie J. M., 2013, Ten new species of Cladonia (Cladoniaceae, Lichenized Fungi) from the Guianas and Venezuela, South America, Phytotaxa 93 (1), pp. 25-39 : 26-27

Cladonia cayennensis Ahti & Sipman , sp. nov. ( Fig. 1 )

Mycobank # MB 803520

Thallus primarius squamulosus, viridifuscus, rotundatus, squamulae 1–2 mm latae, infra sorediosae. Conidiomata et apothecia ignota. Acidum usnicum (parce) et zeorinam (crystallis numerosis in speciminibus diu conservatis) continens. Species epiphytica.

Type:— FRENCH GUIANA. Cayenne : Botanical Garden, on palm, sea level, 04º56’N, 52º20’W, Mar 1985, A. Aptroot 15098 (holotype L!, isotypes B!, H!) .

Primary thallus persistent, consisting of flat to concave, even involute squamules, 1–2 mm wide, soft and fragile, with rounded lobes, entire or little divided; upper side greenish-brown, lower side white, floccose and loosely sorediate, specially along margins; occasionally squamules provided with short basal, brownishveined stalk. Podetia, conidiomata and hymenial discs unknown. Chemistry: usnic acid (in low concentration) and zeorin (needle-like crystals abundant on old herbarium specimens!). Colour reactions: P–, K–, KC–.

Distribution and ecology:— Known so far only from the Guianas, but in view of its occurrence in secondary habitats, the species is probably more widespread. Perhaps it was once reported as C. ahtii S. Stenroos (1989: 252) from adjacent Venezuela, in Bolívar near Canaima, epiphytic at 550 m elev.; this record was excluded from C. ahtii by Ahti (2000). The species was found exclusively epiphytic on hepatic film on smooth, living palm stems in plantations along the coast.

Additional specimen examined (paratype):— SURINAME. Paramaribo: Palmgarden, sea level, Aptroot 14829 (L!) .

Remarks:— Cladonia cayennensis is a sorediate representative of the group of Cladonia miniata G. Meyer (1825: 149) , similar to C. ahtii , from which it differs by the thinner thallus lobes and different chemistry (Ahti 2000). It is also close to C. meridionalis Vainio in Zahlbruckner (1909: 136), but that species has much larger thallus lobes, which are sorediate over much of their lower side. Cladonia termitorum (see below) is also rather similar, due to its slightly sorediate thallus lobes. It differs by its thinner and more finely divided squamules, its chemistry and the regular presence of small podetia and red hymenial discs.

In the absence of apothecia and podetia its systematic position is tentative. It is based on the similarity of its thallus squamules with the miniata group of the genus Cladonia , and its chemistry which occurs in Cladonia rather than in other squamulose lichen genera. Cladonia cayennensis is easily overlooked because it is known only in squamulose, sterile state. However, having a distinct morphology and chemistry, it cannot be any other species of Cladonia recognized by Ahti (2000) in tropical America. Herbarium specimens are easily identified by the soredia and abundant zeorin crystals on the lower surface of the squamules (crystals expected to be absent from fresh material). The presence of a low amount of usnic acid causes hardly any yellowish colour.

Figures

FIGURE 1. Cladonia cayennensis, holotype. Bar = 1 cm.