Pyxine jolyana


Pyxine jolyana is a species of foliose lichen in the family Caliciaceae. It is known from southeastern Brazil, where it grows on rocks and tree bark in coastal and near-coastal areas from sea level to about elevation. The species is distinguished by its brownish-gray rosettes with narrow, pale yellow powdery patches near the lobe edges, and an unusual chemical combination of lichexanthone in the upper layer and norstictic acid in the interior tissue.

Taxonomy

Pyxine jolyana was described as a new species in 2011 by Patrícia Jungbluth, Klaus Kalb, and Marcelo Pinto Marcelli, based on material collected in São Paulo State, Brazil. The species epithet honors Carlos Alfredo Joly for his role in supporting biodiversity work in São Paulo State.
In overall appearance it resembles some other small-lobed, gray-brown members of Pyxine, but it is set apart by its chemistry: it contains lichexanthone in the upper and norstictic acid in the medulla, a combination that is uncommon in South American members of the genus. It is also distinguished by its frequent, pale yellow soralia and by the patchy yellow-to-salmon pigmentation that develops in the upper medulla, which can vary across the thallus.

Description

The thallus is tightly attached to its substrate and usually forms a roughly circular rosette up to about across. It is brownish gray and divided into narrow lobes about 0.5–1.0 mm wide, with rounded to slightly squared-off tips. The upper surface is mostly smooth and lacks isidia or other solid vegetative outgrowths, but soralia are common and tend to sit just inside the lobe margins; the soredia are powdery to slightly granular. The lower surface is black and bears many rhizines of similar color, reaching about 0.7 mm long.
Internally, the medulla is variably colored: it may be cream to pale yellow to salmon in upper parts, and sulphur-yellow beneath soralia, while a thin lower layer can remain white. In older central areas a reddish-purple pigment reaction may appear with potassium hydroxide solution. Pycnidia are rare and occur on the upper surface; the conidia are small and flask-shaped. Chemically, the cortex contains lichexanthone, while the medulla contains norstictic acid along with triterpenes and pigments; the norstictic acid can be unevenly distributed, so spot tests from the lobe tips alone may miss it.

Habitat and distribution

This species was originally known from São Paulo State in southeastern Brazil, with records from coastal and near-coastal localities. It occurs from near sea level up to at least elevation. It has since been recorded from Minas Gerais.
Pyxine jolyana grows either on rock or on bark and woody surfaces. Collections include thalli on coastal rocks, on palm stipes near a river mouth in windy, sun-exposed conditions, and on twigs and tree trunks at the edges of forest.