Cladonia islandica
Cladonia islandica is a species of fruticose lichen in the family Cladoniaceae. It is endemic to Iceland, where it grows on moss-covered rocks and stone walls. The lichen was described as a new species in 2009 by Hördur Kristinsson and Teuvo Ahti. The type specimen was collected by Kristinsson from Herdisarvik, Árnessýsla in 1978. It has been collected from various locations around Iceland, but is most common around the lake Mývatn.
Description
Cladonia islandica is a lichen species with both and growth forms. The primary thallus are persistent, somewhat thick, ranging from convex to flat in shape, and measure 0.2–1.0 mm in length. These squamules show minimal division and appear dark brown and shiny on the upper surface, with a distinctive blackening at the base. The underside displays a texture interspersed with patches of .The podetia are dark brown, taking on a greyish hue in shaded conditions, and have a somewhat shiny surface. The base of these structures shows strong melanisation. These podetia typically stand 3–7 cm tall with a diameter of 0.1–0.5 mm, appearing relatively slender. They may be unbranched or show irregular branching in their upper portions, with some branchlets being long and either curved or spreading at wide angles, culminating in pointed tips. The podetia generally lacking cup-like structures, though narrow cups occasionally form. The are initially closed but may develop perforations as they age.
The surface texture of the podetia is rough, lacking soredia but with microsquamules and coarse. The cortex is discontinuous even in young specimens, relatively thick, and transforms into small, squamules. The medulla is thick but not particularly hard, while the surface of the central canal appears finely . Some larger squamules may be present near the base.
Reproductive structures include infrequent apothecia positioned at the tips of the podetia. These are small, flat, and blackish-brown in colour, though only immature specimens have been observed. Spores have not been documented. The conidiomata are relatively sparse, appearing either at the tips or bases of the podetia, broadly to cylindrical, black, and . Conidia have not been observed.
Chemical spot test analysis shows that Cladonia islandica is K−, and P+. It contains fumarprotocetraric acid as its main secondary metabolite, with traces of protocetraric and confumarprotocetraric acids, as confirmed through thin-layer chromatography.