High diversity at the small scale: an inventory of foliicolous lichens of Brunei reveals 193 species, including 21 new to science

Abstract We present a first comprehensive treatment of the foliicolous lichen biota of Brunei (Brunei Darussalam), a country c. 5765 km 2 in size located on the northern coast of the island of Borneo. Based on a study of numerous leaves collected from 18 sites, resulting in 1745 individual collections, we identified 193 species in the material, including 21 new to science, raising the number of foliicolous lichens known from Brunei from 27 to 199 taxa. This is one of the highest numbers reported for single countries, after Brazil (455 species), Costa Rica (435), Ecuador (365), Mexico (340), Guyana (296), Australia (238), Bolivia and Colombia (228 each), and Papua New Guinea (213). However, relative to log-transformed area size, Brunei is one of the countries with the highest known foliicolous lichen diversity, having almost half the number of species as Costa Rica within an area little more than 10% of the size of the latter. The foliicolous lichen biota of Brunei has a dominant paleotropical element, clustering with that of Indonesia, Malaysia, the Philippines, Papua New Guinea and Australia. The newly described species are: Arthonia concentrica sp. nov., differing from A. trilocularis in the circular thallus with concentrically arranged, thinly pruinose ascomata; Arthonia flavirugosa sp. nov., differing from A. flavoverrucosa in the delicate, light yellowish ridges and the smaller ascospores; Arthonia tenuilobata sp. nov., differing from A. lobulicarpa in the more delicate lobes, pruinose ascomata and the brown ascospores; Byssolecania fumosocaerulea sp. nov., differing from B. fumosonigricans in the greyish blue outer fringe of the apothecia; Byssoloma inconspicuum sp. nov., differing from B. microcarpum in the dark brown apothecial disc and the excipulum lacking crystals; Byssoloma incrustatimurinum sp. nov., differing from B. murinum in the shorter, non-tapering ascospores and the crystals in the excipulum; Byssoloma subaeruginosum sp. nov., differing from B. usambarense in the dark aeruginous hypothecium and the (olive-)brown thallus; Chroodiscus lirellicarpus sp. nov., differing from C. argillaceus in the lirellate apothecia; Chroodiscus minutus sp. nov., differing from C. argillaceus in the very small apothecia; Echinoplaca septemseptata sp. nov., differing from E. tetrapla in the 7-septate ascospores; Eremothecella rugosa sp. nov., differing from E. calamicola in the ridged thallus and the longer conidia; Eremothecella verrucispora sp. nov., differing from E. calamicola in the brown, ornamented ascospores with more numerous septa; Fellhanera tutongensis sp. nov., differing from F. microdiscus in the 3–7-septate, more elongate, narrower ascospores; Mazosia bambusiradiata sp. nov., differing from M. bambusae in the radiately arranged thallus verrucae; Mazosia rugosa sp. nov., differing from M. pseudobambusae in the rugose instead of verrucose thallus surface; Ocellularia andulauensis sp. nov., differing from O. daniana in the more delicate, foliicolous thallus and the much smaller ascospores; Opegrapha albomarginata sp. nov., differing from all other species of Opegrapha with goniocystangia, in the white margin of the goniocystangia; Phylloporis verrucosula sp. nov., differing from P. palmae in the small perithecia and comparatively narrow ascospores; Porina riparia sp. nov., differing from P. pseudoapplanata = Phyllophiale viridis in the finely laciniate thallus with non-radiating photobiont; Spinomyces rubrotrichoides sp. nov., differing from other species in the genus in the multiseptate, worm-like ascospores and from Rubrotricha helminthospora , with which it agrees in ascospore type, in the entirely whitish, more delicate sterile thallus setae; Trichothelium subrobinsonii sp. nov., differing from T. robinsonii in the consistently 7-septate ascospores. The following three species are new continental records: Bapalmuia pallescens (Paleotropics), Lyromma palmae (Paleotropics), and Tapellaria major (Paleotropics). We also include two keys: one to foliicolous species of Arthonia with 2-septate, pigmented ascospores and one to foliicolous species of Porina with Phyllophiale -type isidia.