Melanelixia fuliginosa is chiefly a
saxicolous lichen – it grows on rock. It shows a preference for
siliceous (acidic) rocks such as
granite,
sandstone, and other acidic
outcrops. Typical habitats include boulders, rocky cliffs,
scree, and stone walls in
moorland or
montane areas, especially in regions with clean air and ample rainfall. In these settings it can form extensive dark brown patches on rock faces, often alongside other acid-rock lichens. The species is described as mainly silicicolous (occurring on silica-rich rock). It is usually found in semi-exposed to well-lit conditions; too much deep shade inhibits its growth, while full sun can cause the thallus to become very dark and compact. Although primarily found on rock,
M. fuliginosa has occasionally been recorded on the bark of trees or on old wood (such as fence posts or dead trunks). Such
corticolous (bark-growing) occurrences are more common in humid, coastal or montane woodlands. However, many bark populations historically identified as
M. fuliginosa have turned out to be
Melanelixia glabratula, which favours bark and has a slightly different appearance. In terms of geography,
Melanelixia fuliginosa has a broad Northern Hemisphere distribution. In the wide sense (before separation of
M. glabratula), it was regarded as an almost circumpolar species, found across Europe, Asia, and North America in
temperate to
boreal zones. It occurs on both bark and rock in its range, favouring fairly humid climates and acidic substrates.
M. fuliginosa is widespread in Europe, where it is especially frequent in northern and western regions. For example, it is common in the British Isles (particularly Scotland, Ireland and western England/Wales) on siliceous rocks, and in
Fennoscandia and the Alps. Its European range extends from subarctic areas in Scandinavia and Russia down to mountainous parts of southern Europe (e.g. the
Pyrenees,
Italian Alps, and
Balkan mountains), though it is less common in dry lowland
Mediterranean areas. In Asia, the species (in a broad sense) has been reported in temperate parts of Russia, East Asia, and Central Asia – for instance, in Siberia and high elevations of Korea and Japan (often on rock outcrops in cool climates). Some records also exist from
North Africa (e.g.
Atlas Mountains) and other outlying regions. Reports of
M. fuliginosa from North America have undergone re-evaluation. It was historically cited from both western North America (the Pacific Northwest, Rocky Mountains) and eastern North America (New England and the Appalachians), usually on siliceous rocks in upland areas. These populations were long assumed to be the same species as the European
M. fuliginosa. Recent molecular and taxonomic studies, however, indicate that true
Melanelixia fuliginosa may be absent from North America. Esslinger noted that North American reports of
Melanelia/
Melanelixia fuliginosa were misidentifications of
M. glabratula or other look-alikes. In light of this, North American lichen checklists now exclude
M. fuliginosa in the strict sense, treating the prevalent camouflage lichens on rocks as
M. glabratula or related species. Ecologically,
Melanelixia fuliginosa tends to be an indicator of relatively unpolluted, acidic environments. It tolerates cold and wet conditions well, and can be found from sea level (on coastal rocks) up to
alpine zones (on exposed summits) as long as the substrate is suitable. In areas where it occurs, it contributes to rock surface
communities and provides
microhabitats for small invertebrates. It is not considered
endangered. In the UK, for example, it is rated of
Least Concern due to its broad distribution and commonality. However, distinguishing it from
M. glabratula in the field requires attention to substrate and subtle morphological differences. ==References==