Robust species delimitations provide a foundation for investigating speciation, phylogeography, and conservation. Here we attempted to elucidate species boundaries in the cosmopolitan lichen-forming fungal taxon Lecanora polytropa. This nominal taxon is morphologically variable, with distinct populations occurring on all seven continents. To delimit candidate species, we compiled ITS sequence data from populations worldwide. For a subset of the samples, we also generated alignments for 1209 single-copy nuclear genes and an alignment spanning most of the mitochondrial genome to assess concordance among the ITS, nuclear, and mitochondrial inferences. Species partitions were empirically delimited from the ITS alignment using ASAP and bPTP. We also inferred a phylogeny for the L. polytropa clade using a four-marker dataset. ASAP species delimitations revealed up to 103 species in the L. polytropa clade, with 75 corresponding to the nominal taxon L. polytropa. Inferences from phylogenomic alignments generally supported that these represent evolutionarily independent lineages or species. Less than 10% of the candidate species were comprised of specimens from multiple continents. High levels of candidate species were recovered at local scales but generally with limited overlap across regions. Lecanora polytropa likely ranks as one of the largest species complexes of lichen-forming fungi known to date.

We assess the identification accuracy of ‘research grade’ observations of lichens posted on the online platform iNaturalist. Our results show that these observations are frequently misidentified or lack the necessary chemical and (or) microscopic information for accurate identification. Lichens are a taxonomically difficult group, but they are ubiquitous and eye-catching and are regularly the subject of observations posted on iNaturalist. Therefore, we provide best practice recommendations for posting lichen observations and commenting on observations. Data from iNaturalist are a valuable tool for understanding and managing biodiversity, particularly at this crucial time when large scale biodiversity decline is occurring globally. However, the data must be accurate for them to effectively support biodiversity conservation efforts. Our recommendations are also applicable to other taxonomically difficult taxa.

Premise: Populations of species with large spatial distributions are shaped by complex forces that differ throughout their ranges. To maintain the genetic diversity of species, genepool-based subsets of widespread species must be considered in conservation assessments. Methods: The population genetics of the lichenized fungus Lobaria pulmonaria and its algal partner, Symbiochloris reticulata, were investigated using microsatellite markers to determine population structure, genetic diversity, and degree of congruency in eastern and western North America. Data loggers measuring temperature and humidity were deployed at selected populations in eastern North America to test for climatic adaptation. To better understand the role Pleistocene glaciations played in shaping population patterns, a North American, range-wide species distribution model was constructed and hindcast to 22,000 years before present and at 500-year time slices from then to the present. Results: The presence of two gene pools with minimal admixture was supported, one in the U.S. Pacific Northwest and one in eastern North America. Western populations were significantly more genetically diverse than eastern populations. There was no evidence for climatic adaptation among eastern populations, though there was evidence for range-wide adaptation to evapotranspiration rates. Hindcast distribution models suggest that observed genetic diversity may be due to a drastic Pleistocene range restriction in eastern North America, whereas a substantial coastal refugial area is inferred in the west. Conclusions: Taken together the results show different, complex population histories of L. pulmonaria in eastern and western North America, and suggest that conservation planning for each gene pool should be considered separately.

BackgroundMicrocosms such as pitcher plants, or patches of mosses on a rock surface, have been used worldwide to allow for manipulative experiments that test hypotheses for patterns observed at larger extents, such as dispersal or community assemblage. Such microcosms can also be applied to questions in landscape ecology, but are limited by their binary (patch/non-patch structure). Here we examine a more realistic model landscape system that shares the patch-mosaic structure common to kilometres-extent landscapes. This system of lichen thalli on tree trunks has been shown to have consistent spatial patterns across replicate microcosms, but only when sampling within a limited area. To be relevant for experimentation across scales, it is necessary to determine whether previously observed patterns are consistent when sampling across a broader region and when using different tree species. Here, we test for consistent landscape patch pattern in both maco- and micro-lichens across 21 balsam fir (Abies balsamea) and yellow birch (Betula alleghaniensis) trees.MethodsWe measured spatial pattern of lichen thalli along the trunks of two species of trees, at two spatial resolutions; trees within a single stand (∼100 × 50 m) and trees dispersed across a larger region (500 km2). We used a “lichen ladder” comprised of 5 10 × 10 cm sampling blocks to quantify number of species and individuals in a 50 cm section of the tree trunk. We tested for similar patterns along the trunk and between the north and south sides at both sampling intensities using perMANOVA.ResultsWe find that lichen patches on tree trunks can function as replicate microscoms for landscape ecology. Patterns of thalli along the trunks of trees and between the north and south aspects of the trunk are statistically significantly consistent, although there is variation between tree species, and groups of lichens included. Our microcosm could be used as a model system for landscape ecology research; but researchers should test for consistent patterns first.

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