Lectotypification and Morphological Re-Evaluation of Arthopyrenia molinii Beltr. Based on Historical Material and Comparison with Related Species

Arthopyrenia molinii, described from northern Italy in 1858, has never been formally typified or critically reassessed. In the present study, historical collections preserved in European herbaria were examined to locate and evaluate the original material of the species. A specimen preserved in the A.B. Massalongo Herbarium (VER) is designated here as the lectotype, and A. molinii is redescribed on the basis of the lectotype and additional historical material, with emphasis on thallus, ascomatal, hamathecial and ascospore characters. The species is compared with morphologically similar European taxa, particularly A. parolinii, A. platypyrenia, and the pluriseptate varieties of A. persoonii historically treated as A. grisea. Arthopyrenia molinii is characterized by a persistent epiphloeodal tartareous thallus, relatively large perithecia frequently associated with dark areoles, and narrowly clavate to obclavate, 5–7-septate ascospores. This study establishes a nomenclatural reference for A. molinii and provides a provisional morphological circumscription based on historical material. A. molinii appears morphologically distinguishable from the other pluriseptate taxa examined here; however, because it has not been recollected in recent decades its intraspecific variation and the stability of the diagnostic characters identified cannot be adequately assessed.