Krogia isidiata Kistenich & Timdal

Kistenich, Sonja, Rikkinen, Jouko K., Thues, Holger, Vairappan, Charles S., Wolseley, Patricia A. & Timdal, Einar, 2018, Three new species of Krogia (Ramalinaceae, lichenised Ascomycota) from the Paleotropics, MycoKeys 40, pp. 69-88 : 75-78

Krogia isidiata Kistenich & Timdal sp. nov. Fig. 3

Diagnosis.

The species differs from K. borneensis in forming isidia as vegetative dispersal units, not lacinules, and from the other species in the genus in producing sekikaic and homosekikaic acid.

Type.

New Caledonia, Province Sud, 20 km NNE of Nouméa, along dirt mountain road to Mt Dzumac, 3-400 m S of Seismic Station, ca. 22°03'S, 166°25'E, 830 m alt., on unidentified tree trunk in forest near the road, 2005-12-06, A. Elvebakk 05:633 (O L-186393, holotype; CANB, isotype [not seen]) [TLC: sekikaic and homosekikaic acid; GenBank: MH174285 (ITS)].

Description.

Thallus effuse, squamulose; squamules up to 0.4 mm wide, rounded and adnate when young, later becoming somewhat elongated with a crenulate and slightly ascending margin, flattened, green, with scattered patches of red (K+ purple) spots, epruinose, glabrous; margin concolorous with upper side, not fibrillose; lower side white; isidia attached marginally to the squamules, simple or sparingly branched, up to 1.8 mm long and 0.1 mm wide. Upper cortex composed of a few layers of thick-walled, irregularly or mainly periclinally orientated hyphae with angular to shortly cylindrical lumina, 15-30 µm thick, lacking an epinecral layer, not containing crystals (polarised light!); algal layer 30-40 µm thick, filled with crystals dissolving in K; medulla composed of loosely interwoven hyphae, containing crystals in the upper part; lower cortex lacking; prothallus brownish-black, well developed. Apothecia up to 0.8 mm diam. when simple, often forming aggregates up to 1.6 mm diam., dark reddish-brown to brownish-black, more or less plane, with a rather distinct, concolorous or slightly darker, flexuose margin; excipulum dark reddish-brown throughout, composed of radiating, closely conglutinated, thick-walled hyphae with narrowly cylindrical lumina, inner part containing crystals dissolving in K; hypothecium dark reddish-brown, composed of closely conglutinated, thick-walled hyphae with narrowly cylindrical lumina, containing crystals dissolving in K; epithecium colourless, not containing crystals (but crystals present in hymenium below). Ascospores filiform, curved, simple, spirally arranged in ascus, ca. 20-30 × ca. 1.0 µm (estimate of curved spores). Conidiomata not seen.

Chemistry.

Sekikaic acid (major), homosekikaic acid (major). Spot tests: all negative, except for red patches being K+ purple.

Distribution.

The species is known from four collections at three localities in New Caledonia.

Ecology. The species grows on tree trunks in moist or mesic tropical forests and woodlands (Fig. 5B). All collections are from low-elevation sites and from ultramafic soils typical of the southern part of Grande Terre (main island of New Caledonia). It prefers shaded basal trunks that are otherwise mainly dominated by epiphytic bryophytes and/or leprarioid lichens.

Etymology.

The specific epithet refers to its vegetative dispersal units, isidia.

Remarks.

This species and K. macrophylla are the only isidiate species of Krogia . They differ morphologically mainly in the size and shape of the squamules. In K. isidiata , they are small (up to 0.4 mm wide), rounded and adnate to somewhat elongated and with a slightly ascending margin and, in K. macrophylla , large (up to 3 mm wide), elongated and ascending even when young. In K. isidiata , the squamules are attached to a prothallus, whereas in the latter species, a prothallus has not been observed. The former species contains sekikaic and homosekikaic acid, the latter an unknown compound resembling boninic acid.

Krogia isidiata shares the secondary chemistry with K. borneensis ; see that species for discussion.

Additional specimens examined.

New Caledonia. Province Sud: Yaté, dense forests along road RP 3 about 5 km west of Yaté, on tree trunk, 22°10'03.63"S, 166°54'10.15"E, 410 m alt., 2016-09-20, J. Rikkinen 34385 (H); Blue River Provincial Park, dense riparian forest near camp site on river bank, on tree trunk, 22°05'54.79"S, 166°38'20.24"E, 200 m alt. 2016-09-22, J. Rikkinen 35034 (H); Blue River Provincial Park, dense forest between camp site and road GR NC1, on tree trunk, 22°05'47.63"S, 166°38'22.54"E, 220 m alt., 2016-09-24, J. Rikkinen 35688 (H, PC).