Notes on the genus Usnea Adans. (lichenized Ascomycota, Parmeliaceae) from the islands of Sao Tome and Principe in tropical West Africa

An investigation of the genus Usnea, in the biodiversity hotspot of the Republic of Sao Tome and Principe in tropical West Africa, is presented here. Fifteen species, or species aggregates, were recorded for the islands: Usnea articulata aggr., Usnea baileyi (Stirt.) Zahlbr., Usnea beckeri P. Clerc & Nadel, Usnea bicolorata Motyka, Usnea erinacea aggr., Usnea exasperata (Mull. Arg.) Motyka, Usnea firmula (Stirt.) Motyka, Usnea krogiana P. Clerc, Usnea longiciliata P. Clerc & Nadel, Usnea nodulosa Swinscow & Krog, Usnea pectinata aggr., Usnea sorediosula Motyka, Usnea submollis J. Steiner, and two undetermined species. Two species of lichen are described as new to science: U. beckeri and U. longiciliata. Both species are characterized by a dense and brittle, dark green thallus, the presence of apothecia surrounded by long cilia-like fibrils, a lack of soredia, and the presence of two unknown substances; however, whereas U. beckeri has a pendant growth form and can reach 25 cm in length, U. longiciliata is differentiated by a shrubby growth form of less than 6 cm. These two species also have different ascospore dimensions. A molecular phylogenetic analysis is presented that lends support to their description as new species. Additionally, Usnea krogiana is noted as new to continental Africa and nine Usnea species or aggregates are noted as new to the Islands of Sao Tome and Principe in the Gulf of Guinea.

Automated summary

An investigation of the Usnea genus in the biodiversity hotspot of Sao Tome and Principe in tropical West Africa reveals the presence of 15 species or species aggregates, including two newly described species. The study also notes the new occurrence of Usnea krogiana in continental Africa and the discovery of nine new Usnea species or aggregates in the Islands of Sao Tome and Principe.