Punctelia graminicola

The lichen was first formally described in 1942 as a new species by French lichenologist Maurice Bouly de Lesdain, as Parmelia graminicola. The type specimens were collected in Las Vegas, New Mexico by Brother Arsène Brouard, near the Chimayo Dam at an altitude of 1,900 m (6,200 ft).[5] Although the specific epithet graminicola suggests Gramineae as the substrate,[6] Bouly indicates that the lichen was found growing on mosses and the spikemoss Selaginella.[5] Bouly de Lesdain kept this material, and other collections sent to him by Brouard, at his private herbarium in Dunkirk.[7] The herbarium was destroyed during the bombing of Dunkerque in World War II, and his collections were destroyed.[2] After the loss of the type material, the name Parmelia graminicola was often later relegated to synonymy with Punctelia subrudecta.[8][9][10] In his original description of Parmelia graminicola, Bouly de Lesdain had noted its similarity to P. subrudecta.[5]

In 1980, William and Chicita Culberson reported their observations on the differences in the length of the conidia in populations of Parmelia hypoleucites collected from Arizona and Mexico. They noted that the long-form conidia morphs (P. hypoleucites) grew on bark and had a range restricted to woodlands of the Mexican highlands, while the short-form conidia morphs grew on rocks and were widespread in south-central North America, with few occurrences in regions with the long-form morph. They used this dimorphism to distinguish the short-form morph as a distinct species, P. semansiana, using the larger of Müller's specimens as the type of this new species.[3] Hildur Krog transferred Parmelia semansiana and 21 other Parmelia species with rounded (punctate) pseudocyphellae to the newly circumscribed genus Punctelia in 1982.[4]

In 2001, Robert Shaw Egan discovered that some of Brouard's collections had been rescued from being disposed at a local (New Mexico) landfill, the specimens were transferred to Arizona State University and curated. Among the lichens were isotype of Brouard's collections of Parmelia graminicola that he collected in 1935 near the Chimayó dam. P. semansiana was found to be identical with P. graminicola.[2]

The thallus of Punctelia graminicola measures 3.0–14.5 cm (1.2–5.7 in) in diameter.[6] It comprises irregularly branched lobes, often crowded or overlapping, measuring 2–4 mm (0.08–0.16 in) wide. The upper thallus surface is blue-grey, often with brown margins, and usually smooth and without pruina. Pseudocyphellae on the thallus surface range in number from occasional to abundant. They are circular to irregularly shaped,[11] measuring 0.03–0.6 by 0.03–0.4 mm. The medulla is white.[6] Propagules such as isidia or soralia are absent in this species, but sometimes the lichen forms lobules – small lobes (lacinulae) on the lobe margins that project out from the surface.[11] Adriano Spielmann and Marcelo Marcelli have noted that Punctelia graminicola has a broad species concept, as it include individuals both with and without lacinulae.[6] The thallus undersurface ranges in color from pale tan to light to medium brown, with sparse, light-colored rhizines.[11]

Punctelia hypoleucites, shown here, can be distinguished from P. graminicola using microscopic characteristics

Punctelia graminicola occasionally makes apothecia, although they are absent or immature in some individuals. They are cup shaped with a brown disc measuring 3–10 mm (0.1–0.4 in) in diameter. There are often abundant pseudocyphellae on the folded margins of the apothecia. The ascospores are more or less spherical to broadly ellipsoid, translucent, and measure 7–14 by 6–9 μm. Depending on the individual lichen, pycnidia can be rare or abundant. They are immersed in the thallus surface, appearing like brown to black dots. They produce conidia that are usually like short, translucent rods measuring 5–6 by 1 μm; in rare instances the conidia are hooklike (unciform).[11]

The standard lichen spot test results are K+ (yellow), C-, KC-, P-, and UV- in the upper cortex; in the medulla they are K-, KC+ (red), C+ (red), P-, and UV-, indicating the presence of lecanoric acid.[11]

Punctelia hypoleucites is quite similar in appearance, and can be reliably distinguished from Punctelia graminicola by the length of its conidia (11–12 μm).[3] Unlike Punctelia graminicola, which grows on both rock and bark (the latter much less frequently), Punctelia hypoleucites only grows on bark.[12]

Punctelia graminicola grows on rocks, or on mosses that are on rocks. Much less frequently, it grows on bark. Recorded bark substrates include Fouquieria, Cupressus, and Quercus.[11] In the United States, Punctelia graminicola occurs in the central US east to the Appalachians.[12] In Mexico it is widely distributed across the northern and central parts of the country.[11] Its South American distribution includes Argentina and Brazil.[6] It has also been recorded from East Africa (as P. semansiana).[13]