Sticta venosa Lücking, Moncada & Robayo
Mycobank MB 517812
Thallus growing on the ground between mosses and hepatics, up to 15 cm diam., individual lobes up to 10 cm long, linear to slightly flabellate, 3–5 mm wide, much branched especially towards the tip; upper and lower surface strongly and reticulately ridged, appearing faveolate. Photobiont cyanobacterial (Nostoc). Upper surface blue-grey with brownish tinge when fresh, pale brownish grey when dry, glabrous; lower surface white to yellowish white, glabrous except for thin lines of dark brown tomentum growing on top of the ridges and forming distinct, thin, radiating veins; tomentum up to 2 mm thick, formed by strongly branched and partly conglutinated hairs with cylindrical cells; cyphellae scattered, minute, up to 0.15 mm diam., with pore-like opening (thelotremoid), white, K–. Lobe margins much incised and crenulate, with tufts of up to 0.5 mm long, dark brown hairs growing from the incisions especially at the lobe tips; lobe margins otherwise and towards the thallus center forming numerous marginal isidia, isidia terete to flattenend, unbranched to branched and partly resembling phyllidia, 0.05 mm wide and up to 0.5 mm long, of the same color as the upper lobe surface. Upper cortex paraplectenchymatous, consisting of 1–2 cell layers, 15–25 µm thick, hyaline; cyanobacterial layer 25–50 µm thick; medulla composed of longitudinally oriented, more or less compacted hyphae, up to 100 µm thick; lower cortex paraplectenchymatous, consisting of a single cell layer from which the tomentum emerges, 15–25 µm thick, brown, cells with rounded outer surface. Apothecia not observed. Secondary chemistry: no substances detected by TLC; thallus and medulla C–, K–, P–.
This new species is similar and closely related to Sticta filicinella Nyl., which agrees in the substrate and general lobe morphology including the cyanobacterial photobiont. We examined an isotype of the collection cited in the protologue of Sticta filicinella and the specimen also exhibits the thin white veins on the lower surface partially covered with lines of brown tomentum; that material lacks isidia but bears apothecia instead. Sticta venosa can therefore be considered the isidiate counterpart of S. filicinella. The distinctly ridged and foveolate lobe surface forming veins on both sides and the tomentum on the lower side following these veins give the appearance of a Peltigera or a Lobaria of the L. peltigera group. The new species somewhat resembles the enigmatic submersed lichen formerly known as Hydrothyria venosa J. L. Russell (Peltigera hydrothyria Miadl. & Lutzoni), but can immediately be separated by its terrestrial ecology and the presence of cyphellae on the lobe underside.
The epithet refers to the distinct veins formed by the ridges and the tomentum following the ridges on the lower side.
The species is known from a rich collection from the type locality, growing in the shaded understory of a montane rainforest.
Type:—ECUADOR. Pichincha: Río Guajalito Protected Forest, 0°09’S, 78°39’W, 1800 m; montane rainforest, on ground between mosses; Sep 2008, Lücking 26252 (holotype QCNE; isotype F).
Additional specimens examined (paratypes):—None.
Sicut Sticta filicinella sed thallo foveolato isidiate et tomento venoso differt.