Punctelia bolliana
Punctelia bolliana, the eastern speckled shield lichen, is a species of foliose lichen in the family Parmeliaceae. It is found in North America, with a distribution extending from the Canadian province of Ontario south to the central and northeastern United States and Mexico. It grows on the bark of both deciduous trees and coniferous trees. The combination of characteristics that distinguishes this species from others in genus Punctelia are the absence of the vegetative propagules isidia and soralia, a pale brown lower thallus surface, and the presence of the secondary chemical protolichesterinic acid in the medulla.
Taxonomy
The lichen was first formally described as Parmelia bolliana by Swiss lichenologist Johannes Müller Argoviensis in 1877. The type specimen was collected in Van Zandt County, Texas. In 1982 Norwegian botanist Hildur Krog transferred it to Punctelia, a genus she circumscribed to contain Parmelia species with point-like pseudocyphellae. In North America it is known colloquially as the "eastern speckled shield lichen".Description
Punctelia bolliana has a bluish-grey thallus comprising lobes measuring wide. The surface of the thallus tends to become folded and wrinkled with age, and it develops small lobes on its edges and surface. Isidia and soralia are absent; the lobules are thought to function as a vegetative propagule, although they are noted to be "robust and not easily fragmenting". The thallus underside is pale tan, with pale rhizines. Apothecia are often abundant ; they measure in diameter, with convex or convoluted brown discs. Pycnidia are usually abundant; they appear as tiny light brown to black dots on the surface. The medulla is white and has a continuous algal layer. The presence of both the lobules and apothecia is quite variable, Egan and Lendemer have suggested "the abundance of one appears to be somewhat inversely proportional to the abundance of the other". The ascospores of this species are translucent, more or less ellipsoid in shape, and measure 11–15 by 5–9 μm. The conidia are short with a rod-like shape, measuring 4–5 μm long.Standard chemical spot tests can be used to help identify Punctelia bolliana, or to distinguish it from other Punctelia species. In the medulla, these results are PD−, K−, KC−, and C−; in the upper cortex, they are K+, C−, KC−, and P−. The lichen contains the secondary chemicals protolichesterinic acid and lichesterinic acid in the medulla, and atranorin and minor amounts of chloroatranorin in the cortex.
The set of characteristics that define Punctelia bolliana and differentiate it from other members of the genus are: the absence of soralia and isidia; a brown lower thallus surface; fatty acids in the medulla ; hook-like conidia; and ascospores that measure less than 20 μm. Molecular phylogenetic analysis shows that it is closely related to Punctelia appalachensis, a North American species that also has fatty acids as the main medullary component.