Lichen Systematics: The Role of Morphological and Molecular Data to Reconstruct Phylogenetic Relationships

Integrative taxonomy confirms three species of Coniocarpon (Arthoniaceae) in Norway

We have studied the highly oceanic genus Coniocarpon in Norway. Our aim has been to delimit species of Coniocarpon in Norway based on an integrative taxonomic approach. The material studied comprises 120 specimens of Coniocarpon, obtained through recent collecting efforts (2017 and 2018) or received from major fungaria in Denmark, Finland, Norway and Sweden, as well as from private collectors. We have assessed (1) species delimitations and relationships based on Bayesian and maximum likelihood phylogenetic analyses of three genetic markers (mtSSU, nucITS and RPB2), (2) morphology and anatomy using standard light microscopy, and (3) secondary lichen chemistry using high-performance thin-layer chromatography. The results show three genetically distinct lineages of Coniocarpon, representing C.cinnabarinum, C.fallax and C.cuspidans comb. nov. The latter was originally described as Arthoniacinnabarinaf.cuspidans and is herein raised to species level. All three species are supported by morphological, anatomical and chemical data.

Multiple historical processes obscure phylogenetic relationships in a taxonomically difficult group (Lobariaceae, Ascomycota)

In the age of next-generation sequencing, the number of loci available for phylogenetic analyses has increased by orders of magnitude. But despite this dramatic increase in the amount of data, some phylogenomic studies have revealed rampant gene-tree discordance that can be caused by many historical processes, such as rapid diversification, gene duplication, or reticulate evolution. We used a target enrichment approach to sample 400 single-copy nuclear genes and estimate the phylogenetic relationships of 13 genera in the lichen-forming family Lobariaceae to address the effect of data type (nucleotides and amino acids) and phylogenetic reconstruction method (concatenation and species tree approaches). Furthermore, we examined datasets for evidence of historical processes, such as rapid diversification and reticulate evolution. We found incongruence associated with sequence data types (nucleotide vs. amino acid sequences) and with different methods of phylogenetic reconstruction (species tree vs. concatenation). The resulting phylogenetic trees provided evidence for rapid and reticulate evolution based on extremely short branches in the backbone of the phylogenies. The observed rapid and reticulate diversifications may explain conflicts among gene trees and the challenges to resolving evolutionary relationships. Based on divergence times, the diversification at the backbone occurred near the Cretaceous-Paleogene (K-Pg) boundary (65 Mya) which is consistent with other rapid diversifications in the tree of life. Although some phylogenetic relationships within the Lobariaceae family remain with low support, even with our powerful phylogenomic dataset of up to 376 genes, our use of target-capturing data allowed for the novel exploration of the mechanisms underlying phylogenetic and systematic incongruence.

Two new species of Endocarpon (Verrucariaceae, Ascomycota) from China

Endocarpon species are key components of biological soil crusts. Phenotypic and systematic molecular analyses were carried out to identify samples of Endocarpon collected from the southeast edge of the Tengger Desert in China. These morphological and molecular analyses revealed two previously undescribed species that form highly supported independent monophyletic clades within Endocarpon. The new taxa were named Endocarpon deserticola sp. nov. and E. unifoliatum sp. nov. Furthermore, our results indicated that the newly developed protein coding markers adenylate kinase (ADK) and ubiquitin-conjugating enzyme h (UCEH) are useful for assessing species boundaries in phylogenic analyses.

Circumscription of the genus Lepra, a recently resurrected genus to accommodate the "Variolaria"-group of Pertusaria sensu lato (Pertusariales, Ascomycota)

Pertusarialean lichens include more than 300 species belonging to several independent phylogenetic lineages. Only some of these phylogenetic clades have been comprehensively sampled for molecular data, and formally described as genera. Here we present a taxonomic treatment of a group of pertusarialean lichens formerly known as “Pertusaria amara-group”, “Monomurata-group”, or “Variolaria-group”, which includes widespread and well-known taxa such as P. amara, P. albescens, or P. ophthalmiza. We generated a 6-locus data set with 79 OTUs representing 75 species. The distinction of the Variolaria clade is supported and consequently, the resurrection of the genus Lepra is followed. Thirty-five new combinations into Lepra are proposed and the new species Lepra austropacifica is described from mangroves in the South Pacific. Lepra is circumscribed to include species with disciform ascomata, a weakly to non-amyloid hymenial gel, strongly amyloid asci without clear apical amyloid structures, containing 1 or 2, single-layered, thin-walled ascospores. Chlorinated xanthones are not present, but thamnolic and picrolichenic acids occur frequently, as well as orcinol depsides. Seventy-one species are accepted in the genus. Although the distinction of the genus from Pertusaria is strongly supported, the relationships of Lepra remain unresolved and the genus is tentatively placed in Pertusariales incertae sedis.

Resolving evolutionary relationships in lichen-forming fungi using diverse phylogenomic datasets and analytical approaches

Evolutionary histories are now being inferred from unprecedented, genome-scale datasets for a broad range of organismal groups. While phylogenomic data has helped in resolving a number of difficult, long-standing questions, constructing appropriate datasets from genomes is not straightforward, particularly in non-model groups. Here we explore the utility of phylogenomic data to infer robust phylogenies for a lineage of closely related lichen-forming fungal species. We assembled multiple, distinct nuclear phylogenomic datasets, ranging from ca. 25 Kb to 16.8 Mb and inferred topologies using both concatenated gene tree approaches and species tree methods based on the multispecies coalescent model. In spite of evidence for rampant incongruence among individual loci, these genome-scale datasets provide a consistent, well-supported phylogenetic hypothesis using both concatenation and multispecies coalescent approaches (ASTRAL-II and SVDquartets). However, the popular full hierarchical coalescent approach implemented in *BEAST provided inconsistent inferences, both in terms of nodal support and topology, with smaller subsets of the phylogenomic data. While comparable, well-supported topologies can be accurately inferred with only a small fraction of the overall genome, consistent results across a variety of datasets and methodological approaches provide reassurance that phylogenomic data can effectively be used to provide robust phylogenies for closely related lichen-forming fungal lineages.

A multigene phylogenetic synthesis for the class Lecanoromycetes (Ascomycota): 1307 fungi representing 1139 infrageneric taxa, 317 genera and 66 families

The Lecanoromycetes is the largest class of lichenized Fungi, and one of the most species-rich classes in the kingdom. Here we provide a multigene phylogenetic synthesis (using three ribosomal RNA-coding and two protein-coding genes) of the Lecanoromycetes based on 642 newly generated and 3329 publicly available sequences representing 1139 taxa, 317 genera, 66 families, 17 orders and five subclasses (four currently recognized: Acarosporomycetidae, Lecanoromycetidae, Ostropomycetidae, Umbilicariomycetidae; and one provisionarily recognized, 'Candelariomycetidae'). Maximum likelihood phylogenetic analyses on four multigene datasets assembled using a cumulative supermatrix approach with a progressively higher number of species and missing data (5-gene, 5+4-gene, 5+4+3-gene and 5+4+3+2-gene datasets) show that the current classification includes non-monophyletic taxa at various ranks, which need to be recircumscribed and require revisionary treatments based on denser taxon sampling and more loci. Two newly circumscribed orders (Arctomiales and Hymeneliales in the Ostropomycetidae) and three families (Ramboldiaceae and Psilolechiaceae in the Lecanorales, and Strangosporaceae in the Lecanoromycetes inc. sed.) are introduced. The potential resurrection of the families Eigleraceae and Lopadiaceae is considered here to alleviate phylogenetic and classification disparities. An overview of the photobionts associated with the main fungal lineages in the Lecanoromycetes based on available published records is provided. A revised schematic classification at the family level in the phylogenetic context of widely accepted and newly revealed relationships across Lecanoromycetes is included. The cumulative addition of taxa with an increasing amount of missing data (i.e., a cumulative supermatrix approach, starting with taxa for which sequences were available for all five targeted genes and ending with the addition of taxa for which only two genes have been sequenced) revealed relatively stable relationships for many families and orders. However, the increasing number of taxa without the addition of more loci also resulted in an expected substantial loss of phylogenetic resolving power and support (especially for deep phylogenetic relationships), potentially including the misplacements of several taxa. Future phylogenetic analyses should include additional single copy protein-coding markers in order to improve the tree of the Lecanoromycetes. As part of this study, a new module ("Hypha") of the freely available Mesquite software was developed to compare and display the internodal support values derived from this cumulative supermatrix approach.