Abstract
Xanthoparmelia (Parmeliaceae, Ascomycota) is the most species-rich genus of lichen-forming fungi. Species boundaries are based on morphological and chemical features, varying reproductive strategies and, more recently, molecular sequence data. The isidiate Xanthoparmeliamexicana group is common in arid regions of North and Central America and includes a range of morphological variation and variable secondary metabolites – salazinic or stictic acids mainly. In order to better understand the evolutionary history of this group and potential taxonomic implications, a molecular phylogeny representing 58 ingroup samples was reconstructed using four loci, including ITS, mtSSU, nuLSU rDNA and MCM7. Results indicate the existence of multiple, distinct lineages phenotypically agreeing with X.mexicana. One of these isidiate, salazinic acid-containing lineages is described here as a new species, X.pedregalensis sp. nov., including populations from xerophytic scrub vegetation in Pedregal de San Angel, Mexico City. X.mexicana s. str. is less isidiate than X.pedregalensis and has salazinic and consalazinic acid, occasionally with norstictic acid; whereas X.pedregalensis contains salazinic and norstictic acids and an unknown substance. Samples from the Old World, morphologically agreeing with X.mexicana, are only distantly related to X.mexicana s. str. Our results indicate that X.mexicana is likely less common than previously assumed and ongoing taxonomic revisions are required for isidiate Xanthoparmelia species.
Highlights
The family Parmeliaceae is the largest family of lichenised fungi (Jaklitsch et al 2016) currently classified in approximately 70 genera with almost 2,800 species (Lumbsch and Huhndorf 2010, Divakar et al 2017)
DNA sequences were generated for four markers using polymerase chain reaction (PCR): the nuclear ribosomal internal transcribed spacer region (ITS), a fragment of nuclear large subunit rDNA, the nuclear protein-coding marker minichromosome maintenance complex component 7 (MCM7) and a fragment of the mitochondrial small subunit rDNA
Illumina reads of each specimen were mapped to reference marker sequences downloaded from Genbank (ITS AY581063, nuclear large subunit rDNA (nuLSU) HM125760, MCM7 HM579689, mitochondrial small subunit rDNA (mtSSU) KR995373) using the mapping feature implemented in Geneious v11.0.3
Summary
The family Parmeliaceae is the largest family of lichenised fungi (Jaklitsch et al 2016) currently classified in approximately 70 genera with almost 2,800 species (Lumbsch and Huhndorf 2010, Divakar et al 2017). Isidiate Xanthoparmelia species are distributed in boreal, temperate and tropical regions. In North and Central America, Xanthoparmelia mexicana (Gyelnik) Hale ranks amongst the most common isidiate species. This taxon is widely distributed and has been reported from western USA, Mexico, Dominican Republic, Argentina, Kenya, Australia, New Zealand, Japan, China and Nepal (Hale 1990, Elix 1994, Nash and Elix 2004). To better understand the evolutionary history of the Xanthoparmelia mexicana complex and potential taxonomic implications, isidiate Xanthoparmelia specimens were collected from different locations throughout arid regions of Mexico and supplemented with previously available sequence data. We focused on sampling Xanthoparmelia populations that were phenotypically similar to X. mexicana, e.g. isidiate specimens containing salazinic acid. Based on the results of this study, we formally describe a previously unrecognised species-level lineage comprised of isidiate specimens as new to science
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