Gibbosporina, a new genus for foliose and tripartite, Palaeotropic Pannariaceae species previously assigned to Psoroma

Abstract

AbstractReports of ‘Psoroma sphinctrinum’ from Palaeotropical areas are shown to represent instead species of the genus Gibbosporina, which is described here as new to science. This genus is superficially similar to tripartite, austral Pannaria species, such as the species now referred to as Pannaria sphinctrina (Mont.) Tuck. ex Hue. A phylogram based on an analysis of the nuclear large subunit rDNA (LSU) locus shows that Gibbosporina is instead a clade in a Pannariaceae branch referred to as the ‘Physma group’, a most unexpected addition to Pannariaceae dealt with by several previous studies. Genera assigned to this group have very contrasting general appearances. However, this diverse group shares distinctly ring-like thalline excipular margins; strongly amyloid internal ascus structures; well-developed perispores which have irregular gibbae and/or nodulose or acuminate apical extensions, but not verrucae; lacks TLC-detectable secondary compounds and have tropical distributions. Gibbosporina is the only tripartite genus in the group, with distinct, nodulose, placodioid, mini-fruticose to mini-foliose cephalodia with a high diversity of Nostoc cyanobionts. The cyanomorphs can apparently exist independently in some cases, although the apothecia on such cephalodia on a specimen from Réunion were unexpectedly found to belong to the chloromorph. The genus and related genera forming the ‘Physma group’ are probably evolutionarily old, and their weak affinity to the remaining part of Pannariaceae, concentrated in the Southern Hemisphere, is discussed. The genus includes 13 known species, and the generitype is Gibbosporina boninensis from the Japanese Ogasawara Islands, originally described as Psoroma boninense and recombined here. The following 12 species are described here as new to science, seven of them with molecular support in an LSU and ITS-based phylogram: Gibbosporina acuminata (Australia, the Philippines), G. amphorella (New Caledonia), G. bifrons (Malaysia, New Caledonia, the Philippines, Solomon Islands), G. didyma (Mauritius, Réunion), G. elixii (Australia), G. leptospora (Australia, Papua New Guinea), G. nitida (Australia, Papua New Guinea, the Philippines), G. mascarena (Mauritius, Réunion, Sri Lanka), G. papillospora (the Philippines), G. phyllidiata (Solomon Islands), G. sphaerospora (Australia, Indonesia, Malaysia, the Philippines, Samoa, and with Psoroma sphinctrinum var. endoxanthellum as a new synonym), and G. thamnophora (Australia and the Philippines). Except for the phyllidiate G. phyllidiata and for G. thamnophora which has cephalodia adapted for vegetative propagation, the species are all primarily fertile. A key for determining the species is provided.