Premise

Lichens are fungi that enter into obligate symbioses with photosynthesizing organisms (algae, cyanobacteria). Traditional narratives of lichens as binary symbiont pairs have given way to their recognition as dynamic metacommunities. Basidiomycete yeasts, particularly of the genus Cyphobasidium, have been inferred to be widespread and important components of lichen metacommunities. Yet, the presence of basidiomycete yeasts across a wide diversity of lichen lineages has not previously been tested.

Methods

We searched for lichen‐associated cystobasidiomycete yeasts in newly generated metagenomic data from 413 samples of 339 lichen species spanning 57 families and 25 orders. The data set was generated as part of a large‐scale project to study lichen biodiversity gradients in the southern Appalachian Mountains Biodiversity Hotspot of southeastern North America.

Results

Our efforts detected cystobasidiomycete yeasts in nine taxa (Bryoria nadvornikiana,Heterodermia leucomelos, Lecidea roseotincta, Opegrapha vulgata, Parmotrema hypotropum,P. subsumptum, Usnea cornuta, U. strigosa, and U. subgracilis), representing 2.7% of all species sampled. Seven of these taxa (78%) are foliose (leaf‐like) or fruticose (shrubby) lichens that belong to families where basidiomycete yeasts have been previously detected. In several of the nine cases, cystobasidiomycete rDNA coverage was comparable to, or greater than, that of the primary lichen fungus single‐copy nuclear genomic rDNA, suggesting sampling artifacts are unlikely to account for our results.

Conclusions

Studies from diverse areas of the natural sciences have led to the need to reconceptualize lichens as dynamic metacommunities. However, our failure to detect cystobasidiomycetes in 97.3% (330 species) of the sampled species suggests that basidiomycete yeasts are not ubiquitous in lichens.

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Diatoms are the most diverse lineage of algae, but the diversity of their chloroplast genomes, particularly within a genus, has not been well documented. Herein, we present three chloroplast genomes from the genus Halamphora (H. americana, H. calidilacuna, and H. coffeaeformis), the first pennate diatom genus to be represented by more than one species. Halamphorachloroplast genomes ranged in size from ~120 to 150 kb, representing a 24% size difference within the genus. Differences in genome size were due to changes in the length of the inverted repeat region, length of intergenic regions, and the variable presence of ORFs that appear to encode as-yet-undescribed proteins. All three species shared a set of 161 core features but differed in the presence of two genes, serC and tyrC of foreign and unknown origin, respectively. A comparison of these data to three previously published chloroplast genomes in the non-pennate genus Cyclotella (Thalassiosirales) revealed that Halamphora has undergone extensive chloroplast genome rearrangement compared to other genera, as well as containing variation within the genus. Finally, a comparison of Halamphora chloroplast genomes to those of land plants indicates diatom chloroplast genomes within this genus may be evolving at least ~4–7 times faster than those of land plants. Studies such as these provide deeper insights into diatom chloroplast evolution and important genetic resources for future analyses.

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Recent lichenological investigations of Fox Hills Formation sandstone outcrops in Colorado resulted in the discovery of three populations that represent an undescribed member of the Lecanora dispersa group (¼Myriolecis). This new species is different from all others in the group in its production of usnic acid, which yields apothecia that are yellowish-green in color in fresh field material. The new species, here formally described as Lecanora lendemeri, is further characterized by its relatively large ascospores, endolithic thallus, presence of POLþ granules, and apparent restriction to this sandstone formation. We conducted molecular phylogenetic analyses to place the new species into the context of other members of Lecanora using new shotgun sequence data generated for this study in tandem with previously published rDNA data, and found that the new species is resolved as nested within the L. dispersa group, which was a strongly supported clade in our analysis. Using IUCN criteria including a known occurrence of only three populations, the largest of which is under conservation threat, we herein formally rank this new species as Endangered. This discovery comes on the heels of several other recent lichen discoveries on Fox Hills Sandstone, all species that are, so far as known, restricted to this rock type, suggesting that substrate endemism may be a common element of the biotic communities of the Fox Hills Formation. From the results of this and prior studies, it is clear that sandstone outcrops serve as important, yet still incompletely documented, habitats for cryptogamic diversity. This discovery further highlights the significance of conservation areas, even tiny units (e.g., 40 ha or less) that represent mere islands in a sea of urban development, such as in the Front Range of Colorado.

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