A new arbuscular mycorrhizal (AM) fungus was found in Sierra Nevada National Park of Andalucía (Southern Spain). It forms intraradical hyphae, vesicles and arbuscles, typical characteristics of Glomeromycetes. The spores are dark reddish brown to dark reddish black, 132-205 μm diam, and are formed on pigmented subtending hyphae whose pores are regularly closed by a thick septum at the spore base but without support of introverted wall thickening. Phylogenetic analyses on concatenate sequences of the partial SSU, ITS region and the partial LSU of the rDNA confirm the new species, described here as Septoglomus altomontanum, in a monophyletic clade next to S. africanum. An identification key to all Septoglomus species described is given. The new fungus can unequivocally be distinguished from all other Septoglomus species by the combination of spore size, colour and spore wall structure, and especially by the shape and colour of the subtending hyphae. Septoglomus altomontanum has so far been found only in soils with pH 5.9-6.7, located in mountainous and alpine altitudes (1800-3100 m asl) of Sierra Nevada which is well known for a high degree of plant endemism. While it is a frequent fungus in this area, it has so far not been found in lower altitudes in Andalucía.
Keywords: DNA phylogeny; Glomeromycota; biodiversity; conservation biology; systematic.