According to International Union for the Conservation of Nature (IUCN) guidelines, all species must be assessed against all criteria during the Red Listing process. For organismal groups that are diverse and understudied, assessors face considerable challenges in assembling evidence due to difficulty in applying definitions of key terms used in the guidelines. Challenges also arise because of uncertainty in population sizes (Criteria A, C, D) and distributions (Criteria A2/3/4c, B). Lichens, which are often small, difficult to identify, or overlooked during biodiversity inventories, are one such group for which specific difficulties arise in applying Red List criteria. Here, we offer approaches and examples that address challenges in completing Red List assessments for lichens in a rapidly changing arena of data availability and analysis strategies. While assessors still contend with far from perfect information about individual species, we propose practical solutions for completing robust assessments given the currently available knowledge of individual lichen life-histories.

Phylloblastia iranica S. Kazemi, Lücking & Sipman sp. nov. is described and illustrated as a new foliicolous lichen. It is characterized by 1-septate, colourless, more or less fusiform, slightly curved ascospores, 9–19 × 4–6 μm. In addition, the foliicolous Strigula buxi Chodat is reported for the first time from Iran, increasing the number of foliicolous lichens known from that country to three, where previously only Gyalectidium caucasicum (Elenk. & Woron.) Vězda was recorded. All three species were found in boxwood (Buxus sempervirens) forest. A key to all known Phylloblastia species worldwide is provided.

The phylogenetic relationships of the monospecific genus Paratricharia, with the single species P. paradoxa, within the family Gomphillaceae are resolved using newly generated sequences of the mtSSU and nuLSU markers for three specimens collected in Costa Rica. The results support placement as sister to the genus Caleniopsis, the two genera sister to a clade containing the genera Aulaxina and Aulaxinella. This placement confirms earlier studies based on cladistic analysis of phenotype characters and phenotype-based phylogenetic binning, suggesting that apothecial features are more informative for the phylogenetic placement of taxa within Gomphillaceae than thallus characteristics.

Calicium poculatum and Ramboldia canadensis are described as new species occurring on Larix laricina. Calicium poculatum, currently known from four Canadian provinces and the US state of Minnesota, is characterized by its short-stalked black ascomata, short ascospores and occurrence as a parasite on Lecanora caesiorubella subsp. saximontana. Based on DNA sequence data, its nearest relative is the likewise parasitic Calicium episcalaris. Ramboldia canadensis, currently known only from dead wood of Larix laricina snags in Canada, engages in a fully developed lichen symbiosis with Trebouxia simplex and is characterized in statu symbiotico by having a rimose to verrucose-areolate, greyish creamy sorediate thallus with dark brown to blackish soredia that begin on the margins, and the occurrence of a secondary metabolite similar to barbatolic acid. Phylogenetic analysis recovers it as sibling to a clade of the genus heretofore known only from the Southern Hemisphere and the lower latitudes of the Northern Hemisphere. We also report Lecidella xylophila as new to North America.

We investigated the influence of availability as well as type of organic substrate on the growth of the cyanolichen Peltigera membranacea. A total of 145 lichen lobes were grown in a plant growth chamber for 28 days. Of these, 73 were kept in permanent darkness and another 72 were exposed to a diurnal light-dark cycle. A third of the lobes from both treatments were grown on pulverized leaf litter, the second third on pulverized bryophytes, and the remainder were grown without an organic substrate to serve as a control group. Growth was quantified via relative growth rate, relative thallus area growth rate, and changes in specific thallus mass. The lobes kept in a diurnal light-dark cycle showed higher growth rates than those kept in darkness, as is expected for an organism that obtains its carbon from its photoautotrophic symbiosis partner. Furthermore, growth rates were higher in lobes growing on organic substrates. The results show that the availability of an organic substrate positively affects lichen growth in a growth cabinet. Leaf litter led to a higher biomass gain in lichen lobes, whereas area gain was unrelated to substrate type.