Lecanora printzenii

Lecanora printzenii is a species of crustose lichen in the family Lecanoraceae. Originally found in Spain, it was described as new to science in 2011. It shares several characteristics with lichens of the Lecanora varia group but is differentiated by its unique sequence in the internal transcribed spacer (ITS) region of its DNA and by several distinctive physical characteristics.

Taxonomy
Lecanora printzenii was first described by Sergio Pérez-Ortega, Mercedes Vivas Rebuelta, and Josef Hafellner in 2011. The name pays tribute to lichenologist Christian Printzen of Frankfurt, Germany, in recognition of his significant contributions to the taxonomy of yellow Lecanora species.

The species belongs to the Lecanora varia group, whose taxonomy was recently revised by several studies. DNA sequencing and molecular phylogenetic analysis shows that L. printzenii is closely related to other members of this group, such as L. varia, L. burgaziae, and L. densa. The type specimen of L. printzenii was discovered by the first author in August 2007, in the Parque natural de las Lagunas Glaciares de Neila, in the Castilla and León region of Spain. Paratype material of Lecanora printzenii was included in the seventh fascicle of the exsiccata series "Lichenicolous Biota" (no. 176), where it is hosted by an unspecified species of Umbilicaria.

Description
Lecanora printzenii is characterised by its yellowish-green thallus composed of convex, irregularly rounded, and its numerous , which can be either regular in shape or compressed and irregular. Young apothecia are sessile with thick margins that transition from greenish to black, and they feature a narrow yet distinct whitish band on the inner side. Initially rounded, the apothecia become as they mature, and they become constricted at the base and cup-shaped. Older apothecia are flat, narrowly attached, and have a much thinner margin. The apothecial transition from yellowish-green to melanised and can range from bare to somewhat. This melanization of both the apothecial margin and the disc is a feature that helps to differentiate it from its close relatives. The partner of the lichen is a green alga from the genus Trebouxia with cells that are up to 20 μm in diameter.

Lecanora printzenii is chemically characterised by both usnic acid and psoromic acids as main substances.

Similar species
Lecanora printzenii belongs to the L. varia species group and is closely related to other species of the group such as L. varia, L. burgaziae, and L. densa. However, it is distinguished from these relatives by its lichenicolous habit, the that is partly melanized, the blackish disc, and its distinct ITS sequence. Other lichenicolous species of Lecanora, such as L. lasalliae on Lasallia pustulata and L. gyrophorina on Umbilicaria hyperborea, do not belong to the L. varia group and differ in their habit, anatomical characters and chemistry.

Habitat and distribution
Lecanora printzenii is a lichenicolous lichen, meaning it grows on other lichens, and is specifically found on various species of Umbilicaria. It can cause significant damage to the areas of the lichen where it grows. The host range, however, may be broader, as one collection from Poland occurred on Psorinia conglomerata.

The species has been recorded in a number of mountainous regions across Europe including Sierra de Francia in Spain, the Alps in Austria, the Carpathians in Poland, and most crecently in Montenegro on the Balkan Peninsula. That record extends the known distribution of L. printzenii, which is anticipated to occur more broadly.