Graphis caribica
Graphis caribica is a species of lichen in the family Graphidaceae. Originally described from a specimen collected in the Dominican Republic in 1963, it has since been found in several tropical and subtropical regions including Costa Rica, Florida, the Philippines, and Sri Lanka, where it grows in open woodlands. The lichen forms thin yellowish-green crusts on tree bark and produces distinctive script-like reproductive structures that twist and branch across the surface.
Taxonomy
Graphis caribica was formally described in 2012 by Robert Lücking from a Dominican collection gathered by Henry Andrew Imshaug in 1963. The epithet reflects the species' centre of occurrence in the circum-Caribbean region. Within the large script lichen genus Graphis it belongs to the group characterised by prominent that lack a and have at least the upper part of the apothecial wall —that is, impregnated with dark, graphite-like pigment. It is morphologically closest to G. fournieri, but that species has a completely carbonised excipulum and develops brick-walled spores, whereas G. caribica shows carbonisation only at the top of the excipulum and produces narrower, purely transversely-septate spores. No lichen substances were detected by thin-layer chromatography, a feature that further helps separate the new taxon from chemically distinct members of its genus.Description
The lichen forms a thin, continuous crust up to about 5 cm across on tree bark. Viewed from above the surface is uneven and yellow-green and lacks a dark line. In vertical section the outer "skin" is beneath it lies a patchy of green algal cells and conspicuous clumps of colourless crystals, then a white medulla.Fruiting bodies are conspicuous script-like lirellae 1–5 mm long and 0.3–0.4 mm wide that twist flexuously and branch sparsely. They emerge well above the thallus surface and show no enveloping ; instead the true margin is thick, pale and longitudinally striate, while the itself remains concealed. Microscopic examination reveals a scalloped that is jet-black only around the summit but grades to pale yellow-orange at the sides and base. The hymenium is clear, 120–150 μm tall, and surmounted by a finely granular olive-brown cap. Each club-shaped ascus contains eight colourless, elongated ascospores 50–65 × 9–12 μm, divided by 9–15 cross-walls; there are no longitudinal walls. Standard chemistry is negative.