Population genetics and biogeography of the lungwort lichen in North America support distinct Eastern and Western gene pools

Abstract

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.

Genomic Resources for the First Federally Endangered Lichen: The Florida Perforate Cladonia (Cladonia perforata)

“…In a circum-Antarctic study of Pseudocyphellaria glabra, Widhelm et al [46] found evidence for clades that largely correspond to continental-level regions with few instances of intercontinental gene flow, thus showing some spatial structure, though on a very large spatial scale. In Lobaria pulmonaria, a species with a circumboreal distribution that is rare and patchily distributed in some parts of its range, there is evidence for high levels of isolation by distance in some parts of its range [56] and evidence for gene pools with very large distributions in other parts of its range [57], which is perhaps driven by differing landscapelevel processes occurring among sampled regions. The hypothesized relationship between rarity and migration rates in LFFs remains to be tested in a rigorous framework.…”

Phylogenetic insight into the Lecidea atrobrunnea complex – evidence of narrow geographic endemics and the pressing need for integrative taxonomic revisions

“…Understanding the processes and factors that have shaped the diversity and distribution of the L. atrobrunnea complex remains enigmatic. How historical processes (Otálora et al 2010; Fernández-Mendoza & Printzen 2013; Widhelm et al 2019), isolation by distance (Walser et al 2005; Widhelm et al 2021), niche differentiation (Guttová et al 2019; Allen et al 2021; Moncada et al 2021) and other factors interacted to give rise to the species diversity in the L. atrobrunnea complex remains to be explored. A robust, comprehensive reconstruction of the evolutionary history of the L. atrobrunnea complex is lacking, and our study highlights the potential of genome-scale datasets for resolving relationships within this complex (Fig.…”

Circadian clock and temperature-associated genes vary along climate gradients in lichenized fungi

“…Variation along environmental gradients in the lichen symbiosis Many species of lichenized fungi have broad geographic and climatic ranges, and exhibit significant population structure (e.g. Allen et al 2021, Fernández-Mendoza et al 2011, Muggia et al 2014. Part of the observed population differentiation can be linked to environmental factors, evidenced, e.g., by abrupt, parallel genomic breaks along elevation gradients, separating populations into high and low elevation genetic clusters, which correspond to different climate zones (Dal Grande et al, 2017, Rolshausen et al, 2020, 2022.…”