Gallowayella weberi

Gallowayella weberi is a species of corticolous and saxicolous (bark- and rock-dwelling), foliose lichen in the family Teloschistaceae. Found in the eastern United States, it is a small lichen with a smooth yellow to orange upper surface and a contrasting white lower surface.

Taxonomy
The lichen was first formally described as a new species in 2003 by the lichenologists Sergey Kondratyuk and Ingvar Kärnefelt, who named it Xanthoria weberii. The type specimen was collected in Grimes County, Texas in 1970. It was found by William Alfred Weber in woodlands dominated by Quercus stellata (Post Oak), where it was abundant on oak trees in both dusty roadside locations and urban areas. The spelling with two "i"s was erroneous, and it was corrected to weberi in a subsequent publication. After a couple more proposed generic transfers, to Oxneria and later to Xanthomendoza, Kondratyuk, Kärnefelt, and their colleagues finally reclassified the taxon in the then newly circumscribed genus Gallowayella in 2012.

Description
Gallowayella weberi is a foliose lichen that forms small thalli up to 4 mm wide, which adhere to surfaces ranging from closely to somewhat loosely attached. The of the thallus are flat, ranging from horizontal to slightly ascending, and measure between 0.3 and 0.5 mm in width. The tips of these lobes often curve inward, and the outermost parts of mature lobes are truncated or cut off squarely.

The upper surface of Gallowayella weberi has a yellow to orange color and is smooth to the touch. Its lower surface contrasts with a white color. The cortex, or the outer layer of the lichen, is made of tightly packed cells and is colorless, except for the presence of external anthraquinone crystals, which are chemical compounds often found in lichens. The (photosynthetic partner) is a unicellular green alga from the genus Trebouxia.

The medulla, which is the inner tissue beneath the cortex, has a net-like structure made of short cells. Rhizines, which are root-like structures helping the lichen to anchor to its, are mostly present and are white in color, turning yellow when exposed. They can be either attached to the substrate or free. Soralia, the structures for asexual reproduction, are found at the lobe tips and often form small structures resembling bird nests, with the soredia (powdery reproductive propagules) being yellow in color.

Apothecia (fruiting bodies) are rare in this species and range from 0.7 to 2.0 mm in width. The measure between 12.7 and 14.0 by 7.0 to 7.7 μm, with a septum thickness of 2.9 to 4.6 μm. Pycnidia, an asexual reproductive structure, are common on the surface and are orange in color, measuring about 0.1 to 0.2 mm in diameter. The conidia (asexual spores) are rod-shaped and measure 3.2 to 3.6 μm in length.

Chemically, the cortex and apothecia react to a solution of potassium hydroxide by turning purple, but show no reaction to other chemical spot tests (C−, PD−, and I−). The medulla also shows no reaction to these tests. The major secondary metabolites (lichen products) found in Gallowayella weberi are parietin, fallacinal, and teloschistin, with emodin and parietinic acid as minor components. This distribution of secondary metabolites corresponds to the A proposed by Ulrik Søchting in 1997.

Habitat and distribution
Gallowayella weberi is found in arid environments and can grow on diverse substrates including both natural surfaces like bark and rock, as well as on artificial ones such as concrete and tombstones. It is native to North America, predominantly in the eastern regions, with its most significant population density in the Southeast.

Species interactions
Tremella xanthomendozae is a lichenicolous fungus that infects Gallowayella weberi (it was named when its host was classified in genus Xanthomendoza).