Lecidea varians is among the most common and abundant bark-dwelling crustose lichens in temperate eastern North America. As presently delimited, it is highly variable, including chemical and morphological diversity well beyond that currently accepted for most lichen species. The generic placement of L. varians has also been questioned for decades. It has long been recognized as aberrant in Lecidea and Pyrrhospora, excluded from Lecidella, and more recently transferred to Traponora. Drawing from the results of extensive chemical, molecular phylogenetic and morphological studies, we show that L. varians and its relatives represent a previously unrecognized lineage within the speciose lichen family Lecanoraceae. The lineage appears to occupy an isolated position, distinct from the aforementioned genera, and is newly described as the genus Xanthosyne (typified by L. varians). The chemical and morphological variation within L. varians is mirrored by, but not entirely correlated with, considerable molecular diversity. A new taxonomy is proposed for L. varians and its relatives to serve as a framework for future studies. Three species are recognized: X. varians (≡ Lecidea varians), common and widespread in parts of North America; X. granularis, a new species from the Atlantic Coast of eastern North America that differs morphologically from X. varians in having a leprose thallus; and X. sharnoffiorum, a new species also found mainly along the Atlantic Coast of eastern North America, which has a coarsely granular, non-leprose thallus and produces a unique, unidentified xanthone. Multiple well-supported lineages were recovered within X. varians that correlate to varying degrees with chemical and morphological variability, as well as geographic distribution. Eight subspecies are recognized to accommodate the variation within X. varians: X. varians subsp. exigua comb. nov. (≡ Lecidea exigua) characterized by the presence of atranorin and a consistent set of three xanthones, is widespread in southern Europe and western North America (coastal California); X. varians subsp. varians (≡ Lecidea varians) is distributed mainly in northeastern North America and produces thuringione and arthothelin; X. varians subsp. morsei subsp. nov. is morphologically and chemically variable, with one chemotype (thiophanic acid) with a northeastern distribution, and the other with a unique and unidentified xanthone, found mainly in the interior U.S.A.; X. varians subsp. obscura subsp. nov. occurs mainly in the central U.S.A. and North Temperate regions, produces a unique, unidentified xanthone and generally has black apothecia with green epihymenial pigments; X. varians subsp. pseudomorsei subsp. nov. and X. varians subsp. submorsei subsp. nov. resemble X. varians subsp. morsei but differ in molecular sequence characters; X. varians subsp. subtilis comb. nov. (≡ Lecidea subtilis) and X. varians subsp. subexigua subsp. nov. occur in the Appalachian Mountains, the former producing atranorin and the latter lacking atranorin, both with thiophanic acid with or without other xanthones. In an addendum, Lecidella subviridis is discussed with respect to the genus Xanthosyne. An identification key is provided for all species and their subspecies within Xanthosyne.

Macrolichen diversity and community composition were determined for an area of high botanical interest in the Coast Ranges of Northern California – the Horse Mountain Botanical Area (HMBA) in Six Rivers National Forest. The Coast Ranges have been suggested to have high lichen diversity, yet detailed site-specific macrolichen surveys are lacking for the area. The HMBA is characterized by the presence of ultramafic (serpentine) soils, contributing to its diverse assemblage of conifers. Here we present comprehensive data on macrolichens of the HMBA integrated with environmental variables at the landscape level. Twenty 0.4 ha sampling plots were positioned across the varying habitats of the HMBA and macrolichens were intensively sampled from all substrata. Out of 888 total collections, 119 macrolichen species in 52 genera were identified, 63 species were sequenced for the mycobiont internal transcribed spacer (ITS) region, and all species were vouchered. Microenvironmental influences on lichen community composition were ordinated with nonmetric multidimensional scaling (NMS). Within-plot measured environmental variables with strongest correlations to ordination Axis 1 were 1) total tree basal area, 2) proportion of conifer basal area relative to hardwoods, and 3) distance between plot center and nearest stream. Distinct macrolichen communities were found in plots containing primarily conifers versus mixed hardwood-conifer plots. All plots contained both nitrogen-fixing and pendulous forage macrolichens; in each of the three hardwood-dominated plots, nitrogen-fixing lichens composed nearly a third of the species total. When epiphytic macrolichen species richness and dominance within the HMBA were compared to data from other regional forests, the HMBA showed comparable community composition but averaged 39% higher species richness. Results from this study can help inform management of the HMBA as well as future taxonomic and ecological research on regional macrolichens.

Conservation of lichens is impeded by knowledge gaps on their distribution and habitat requirements. This is a significant issue in vast, isolated and harsh environment regions such as subarctic regions, where lichen communities remain under documented. Lichen biodiversity assessments provide useful insights to better understand the functions supported by these ecologically important and sensitive species. This study aims i) to describe the conservation status of lichen communities and their α- and β-diversity components across a subarctic region in Northern Quebec (190 km²), ii) to describe their functional traits across the habitat types found in this region, and iii) to identify habitat types constituting lichen biodiversity hotspots. Lichens were sampled in 45 plots in habitats ranging from coniferous and deciduous forests to bogs, fens and rocky outcrops. A total of 115 species of largely macrolichens, calicioid lichens and allied fungi were identified, of which 18% currently have ranks of conservation concern at the provincial level, and 38% are newly reported for the region (∼124,000 km² around our study area). Richness across plots averaged 36 ± 9 species and plots richer in microhabitats often harbored more species (R² = 0.22). Differences in species composition were identified among plots and habitat types through NMDS and perMANOVA analyses (R² = 0.35; p < 0.001), both being supported by differences in microhabitat composition (Mantel r = 0.22 and perMANOVA R² = 0.29, respectively; p < 0.001). Thirty-five species showed significant preferences for a habitat based on the Pearson's phi coefficient of association. Our analysis on functional traits revealed significant patterns of association with habitat types, including i) saxicolous species with rocky outcrops, ii) epiphytic/epixylic species and vegetative reproduction traits (soredia, isidia) with coniferous stands, and iii) species belonging to the Parmeliaceae family with fens. Rocky outcrops represented the main lichen biodiversity hotspots in the region, while other habitat types were also important for maintaining total and complementary biodiversity. We are confident that our methodological approach including systematic sampling, full habitat variability representation, and the evaluation of complementary biodiversity components, can be effectively applied to fill gaps on lichen biodiversity in other underexplored regions across the globe.

The island of Newfoundland, Canada, is known as an area with high lichen species richness; however, most of this diversity is known from coastal regions where the ocean creates a maritime climate. The central part of the island has a more continental climate and is also the part of the province with the highest levels of industrial forest harvest and mining activities. For these reasons, it has not been an area considered to have high lichen diversity. Here, we show how local Mi'kmaw knowledge in collaboration with western scientific expertise facilitated a two-eyed seeing approach (Etuaptmumk) that yielded the discovery of overlooked lichen diversity in Central Newfoundland. Surveys by the authors throughout 2023 yielded collections of 175 species of lichenized, lichenicolous and allied fungi from the area known as Charlie's Place. Of these, there is a high proportion of cyanolichens (13%) and calicioids (11%), indicating high ecological value and potential old growth/ancient forest status. In addition, we report 19 new species records for the province, two of which (Chaenothecopsis vainioana and Myrionora albidula) are new records for Canada. Overall, the survey work reported here suggests that Charlie's Place should be a priority area for protection within the context of Central Newfoundland. This work also illustrates the value of research under the framework of Etuaptmumk and the benefits of combining local Indigenous and western scientific knowledge. The political, logistical, and financial support of Qalipu First Nation was key to the success of this work.