Variospora flavescens
Variospora flavescens is a species of saxicolous, crustose lichen in the family Teloschistaceae. It is a common, widely distributed species and has been recorded in Africa, Asia, Europe, and Macaronesia. It forms large, circular, orange patches up to 10 cm or more across on calcareous stone such as limestone and mortar. First described in 1762, the species has been placed in several genera and was transferred to Variospora in 2013.
Taxonomy
The species was first scientifically described by botanist William Hudson in 1762. He placed it in the eponymously named genus Lichen, as was the standard practice in those times, following the example of Carl Linnaeus in his influential 1753 work Species Plantarum. In its long taxonomic history, the species has acquired an extensive list of synonyms. For example, in early Italian literature, it was frequently referred to as Caloplaca murorum. Jack Laundon placed the taxon in the genus Caloplaca in 1984, and it was known by this binomial until 2013, when Ulf Arup, Patrik Frödén, and Ulrik Søchting transferred it to the newly circumscribed genus Variospora.Description
Variospora flavescens features a thallus, which forms large, evenly distributed, circular patches measuring or more in diameter. The of the thallus are closely, with rounded or irregular shapes. Their surface has a matte texture, varying in colour from pale to deep orange.The lobe-ends of this lichen species are not widened but are rounded and convex. They can sometimes appear faintly, meaning they have a white, waxy, powdery coating. The lobes, which are pleated and sometimes overlapping, are situated close to each other. The centre of the thallus has a closely, uneven texture, composed of occasionally contorted and congested lobes. These central lobes are white and non-pigmented but are spotted with orange apothecia. These apothecia reach up to 1.5 mm in diameter. They are primarily located at the centre of the thallus and are typically abundant and crowded. When young, they are flat but become convex as they age. The, or the border of the apothecia, is the same colour as the initially but becomes excluded over time. The disc varies in colour from orange to orange-brown. In microscopic cross-section viewed under polarised light, the thallus shows small orange crystalline deposits in the upper cortex, while the inner cortex may contain larger, colourless crystals interpreted as calcium oxalate.
The paraphyses are slender and range from straight to, without noticeable swelling at the ends. The lemon-shaped measure 12–15 by 8–10 μm, and are swollen at the septum. The septum's breadth varies, reaching up to 5 μm wide.