Nesolechia oxyspora

The spores, measuring 14–22 by 5–7 μm, are spindle-shaped. The epithecium is chestnut brown, and the hymenium turns blue when treated with iodine (J+). The ascomata (fruiting bodies), which are 0.1–0.4 mm in size, form dense clusters. Initially, they develop inside the lichen thallus, but eventually break through the cortex and slightly protrude. The disc starts off flat with a fine margin, then becomes slightly convex and marginless, with a dull black-brown colour. Studies have revealed considerable variation in spore morphology depending on the host lichen species. When growing on different genera of parmelioid lichens, the fungus produces spores with statistically significant differences in their length-to-breadth ratios. For example, spores from specimens on Parmelia saxatilis have an average length-to-breadth ratio of 3.12, while those on Platismatia glauca average only 2.25. This variation suggests that N. oxyspora may represent a complex of closely related species or strains, each adapted to specific host genera. The colour of the hypothecium (the tissue layer beneath the spore-producing cells) also varies from very pale tan to brown depending on the thickness of the sections examined, and rarely stains positively with iodine. The morphological features of N. oxyspora can be measured in detail across different host species. …

This fungus species appears to be cosmopolitan in distribution. It is found on the thalli of various foliose (leaf-like) and fruticose (shrub-like) lichens, where it sometimes induces the formation of galls.

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