Hypotrachyna rwandensis

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Hypotrachyna rwandensis is a rock-dwelling, leaf-like lichen in the Parmeliaceae family. It was found in 1999 in a high-elevation swamp in southern Rwanda, where it grows exclusively on ancient schist rock. It was described as a new species in 2005 by John Elix, Eberhard Fischer, and Dorothee Killmann. The holotype is kept in Berlin, with an isotype in Canberra. The name honors Rwanda.

This lichen forms rosettes about 5–6 cm across. Its lobes are linear, 1–3.5 mm wide, with tips that are rounded to blunt, and the edges have tiny hair-like projections (cilia). The upper surface is grey and smooth, with dense isidia (vegetative reproductive structures) on the surface. The lower surface is black and attached to the rock by dense, forked rhizines. Apothecia (fruiting bodies) are uncommon. When present, they are 3–5 mm wide with a dark-brown disc and a rim rich in isidia. The spores are ellipsoid, about 13–15 by 8–10 μm.

Chemically, the cortex reacts yellow with a K test and contains atranorin and chloroatranorin. The medulla is negative with K but reacts red with C and KC, and contains major substances gyrophoric acid and 5-O-methylhiascic acid, plus minor lecanoric and hiascic acids. These chemical traits help distinguish it from similar species.

Hypotrachyna rwandensis grows on Precambrian schist in the Rwasenkoko swamp at about 2,350 m, a cold, high-elevation site in Rwanda. The area features a mix of montane and afroalpine plants, with night temperatures that can drop below freezing. As of 2007, it was one of five Hypotrachyna species recorded in Rwanda, with the site also yielding other lichens such as Hypogymnia physodes.