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Alectoria (fungus)
Alectoria is a genus of fruticose lichens belonging to the family Parmeliaceae.[1] TaxonomyThe genus Alectoria was previously placed in the family Alectoriaceae, which was widely accepted as distinct from Parmeliaceae based on differences in reproductive structures such as larger asci, pigmented spores, and distinctive hamathecial characteristics. However, a 1999 molecular phylogenetic study examined the relationship between Alectoriaceae and Parmeliaceae using sequences of nuclear ribosomal DNA. Their analysis included specimens of Alectoria ochroleuca and A. sarmentosa along with various members of the Parmeliaceae. The results showed that Alectoria was derived from within the Parmeliaceae, suggesting the two families should be treated as synonyms. While previous taxonomic work had emphasised differences in ascus structure, spore size, and hamathecial characteristics to justify separating Alectoriaceae, the study concluded that these variations represented extremes within a continuous range of characters found in Parmeliaceae rather than distinct family-level differences. The authors recommended including Alectoria within a broader concept of Parmeliaceae rather than maintaining it in a separate family.[2] DescriptionAlectoria forms shrub-like (fruticose) growths, which can either stand upright, sprawl along surfaces, or hang down from their substrate. The main body thallus) of these lichens appears in colours ranging from greenish-yellow to brownish-black. Their branches are typically rounded and smooth, though in some cases they may become flattened near their base and where branches meet. One subspecies (Alectoria sarmentosa subsp. vexillifera) is considerably different, having distinctly flattened branches with clear upper and lower surfaces.[3] A distinctive feature of Alectoria is the presence of white, spindle-shaped structures called pseudocyphellae, which appear as small pores or marks on the surface. These lichens do not produce isidia or soredia, which are specialised propagules for vegetative reproduction. Like most lichens, Alectoria is a partnership between a fungus and an algal partner (photobiont), specifically one from the Trebouxia genus of green algae.[3] The reproductive structures (apothecia) are rare and appear along the sides of branches. These disc-shaped structures have rims that match the colour of the main body. Inside the apothecia are specialised cells (asci) that produce spores. These thick-walled, club-shaped asci typically contain either two or four spores. The spores themselves are relatively large, single-celled, oval-shaped, and range from colourless to brown, surrounded by a clear outer layer.[3] The genus also produces small, black, globe-shaped structures called pycnidia that are partially or fully embedded in the thallus. These produce rod-shaped to narrow spindle-shaped asexual reproductive cells called conidia. Chemically, almost all species contain usnic acid, and many produce compounds called orcinol and β-orcinol depsides.[3] Species
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