Small island but great diversity: thirty six species of Parmotrema (Parmeliaceae, lichenized Ascomycota), including sixteen new species, on Réunion (Mascarenes), with additional data from the Western Indian Ocean

English. peer reviewed

English. This work is part of our taxonomical and phylogenetic studies on the lichen flora of Réunion (Mascarene Archipelago, Indian Ocean). Thirty-six species belonging to the conspicuous genus Parmotrema are recognized on the island, sixteen being new to science: P. aurantioreagens, P. brachyblepharum, P. crossotum, P. eleonomum, P. intonsum (also found in Madagascar), P. mezierii, P. mascarenense (also found in Mauritius), P. mirum, P. nemorum, P. nephophilum, P. occultum, P. orarium, P. paramascarenense (also found in Madagascar), P. reunionicum, P. subdeflectens (also found in Madagascar) and P. udisilvestre (also found in Madagascar). Parmotrema mwaliense is a further new species found on the island of Mohéli (Comoros). Three new combinations are introduced: Parmotrema inexspectatum, P. meiospermum and P. odontatum. We propose synonymization of P. acrotrychum with P. subcorallinum. The following species are confirmed or reported as new to Réunion: P. austrosinense, P. cetratum, P. cf. clavuliferum, P. cooperi, P. crinitum, P. cristiferum, P. cf. deflectens, P. dilatatum, P. mellissii, P. cf. negrosorientale, P. praesorediosum, P. reticulatum, P. robustum, P. subcorallinum, P. subisidiosum, and P. tinctorum. Parmotrema appendiculatum and P. thomsonii are only known to Réunion from single reports, poorly documented, dating back to the 19th century; detailed descriptions with photographs, distribution maps and ecological data are provided for the other species. An identification key for the 36 species is provided. Parmotrema austrosinense and P. cf. negrosorientale are newly reported, and P. meiospermum confirmed, for Mauritius; the Papuan P. menyamyaense is newly reported for Mohéli (Comoros). One hundred and seventy-four new sequences for the barcode ITS loci have been produced, an increase of ca. one third for Parmotrema on GenBank. LSU, mtSSU and EF1-α loci have been added for subgroups. The molecular data highlight the existence of two pairs of ‘nearly’ cryptic species (P. crinitum/P. occultum, P. brachyblepharum/P. eleonomum), high variability in the production of vegetative propagules in two of the new species described (P. nephophilum, P. orarium), and two strongly supported clades including potential endemics to Réunion or the MIOI (Madagascar and the Indian Ocean Islands) biodiversity hotspot. One clade comprises 10 species (P. brachyblepharum, P. crossotum, P. eleonomum, P. intonsum, P. mezierii, P. cf. negrosorientale, P. nemorum, P. subcorallinum, P. subdeflectens and P. udisilvestre), eight described as new for science, the other five species (P. aurantioreagens, P. mascarenense, P. meiospermum, P. odontatum and P. orarium), three of them new for science.