The family Trypetheliaceae is a diverse lineage of crustose lichenized fungi occurring almost exclusively in the tropics. Based on material collected in eastern Colombia in the region of the so-called Piedemonte Llanero, we describe here a new species for this family, in the genus Marcelaria, the fourth species known in the genus. The new species, Marcelaria casanarensis, is characterized by a clear hamathecium and large ascospores, similar to the neotropical M. purpurina, but it produces orange instead of red superficial pigmentation, outwardly agreeing with the two paleotropical species, M. benguelensis and M. cumingii. The new species thus appears to provide a morphological link between the currently known neotropical and paleotropical taxa. However, the pigment chemistry is closer to that of M. purpurina, so the orange colour is to be interpreted as homoplasy. Phylogenetically, based on an analysis of two markers, M. casanarensis and M. purpurina are closely related but M. casanarensis differs in two larger insertions in two different regions of the mitochondrial small subunit rDNA (mtSSU). A key to the four species currently accepted in Marcelaria is presented.

We present a first comprehensive treatment of the foliicolous lichen biota of Brunei (Brunei Darussalam), a country c. 5765 km2 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.

Lichens have been shown to optimize their photosynthetic apparatus in response to seasonal changes in light and temperature. However, there have been few investigations on seasonal variations in the biochemical mechanisms used by lichen photobionts to protect themselves against the potentially harmful effects of high light. In our earlier work, carried out during the summer months, we showed that Afromontane lichens collected from shaded habitats display higher values of non-photochemical quenching (NPQ) and lower maximum relative electron transport rates (rETRMAX) than thalli collected from sunny habitats. Here we employ chlorophyll fluorescence to show that, in contrast, winter collections of the Afromontane lichens Ramalina celastri and Usnea undulata from a diversity of sites display no significant differences in NPQ and rETRMAX between sun and shade forms. Results suggest that in the winter, shade forms downregulate their NPQ because loss of leaves causes less fluctuation in light levels, but retain similar values of rETRMAX to those of summer collections. Conversely, during the winter, thalli from exposed microhabitats downregulate their rETRMAX, presumably to reflect reduced possibilities for carbon fixation, and retain generally low values of NPQ. All winter collections display similar, high values of cyclic electron flow (CEF) and pseudocyclic electron flow (PCEF), indicating strong photoprotection of photosystem I. Taken together, the results suggest that photobionts can flexibly adjust their photosynthetic apparatus to seasonal variations in light availability.

Small, isolated populations of cold-adapted species at the edge of their climatic range are highly sensitive to environmental change, making them powerful ecological indicators. Cetraria sepincola (Ehrh.) Ach. is an epiphytic lichen which illustrates this role. It is common in Nordic countries, but in the southern parts of its European range, its distribution has become fragmented and restricted to cold habitats. We studied populations in habitats of high conservation value such as wetlands, montane stone fields, and wooded meadows in south-west Germany, where it persists at the edge of its ecological range in Central Europe and is becoming increasingly rare. Its dependence on specific climatic conditions and selectivity in its photobiont associations make it particularly responsive to shifts in climate and land use. Through historical records, recent observations, data on nitrogen deposition and associated species, we identified key environmental factors shaping the distribution of C. sepincola. Our analysis confirms that populations in south-west Germany occur at the climatic margin of the species’ Central European range. We also found that high-density local populations are linked to low ammonia (NH3) concentrations. Cetraria sepincola associated specifically with Trebouxia lineages from clade S (e.g. OTU S28 = Trebouxia barrenoae and OTU S27), commonly found in lichens from acidic substrates. We found the same Trebouxia lineages in the co-occurring acidophyte Hypogymnia physodes (L.) Nyl., a likely local photobiont donor for C. sepincola, which lacks asexual propagules. At some sites, species of the nitrophytic Xanthorion community started to colonize the same twigs as C. sepincola. In our study area, typically more nitrophytic species from the families Teloschistaceae (e.g. Polycauliona polycarpa (Hoffm.) Frödén et al., Xanthoria parietina (L.) Th. Fr.) and Physciaceae (Physcia adscendens H. Olivier) host Trebouxia algae from clades which are incompatible with C. sepincola. The spread of nitrophytic species and their associated photobionts into formerly acidophytic communities could also reduce the likelihood of finding compatible photobionts for C. sepincola. Climate change, possible direct toxic effects of NH3 on the mycobiont, and indirect impact of NH3 on the lichen and photobiont community exacerbate the extinction risk for sensitive lichens, particularly at the edge of their distribution range.