DNA barcoding and LC-MS metabolite profiling of the lichen-forming genus Melanelia: Specimen identification and discrimination focusing on Icelandic taxa

Abstract

Taxa in the genus Melanelia (Parmeliaceae, Ascomycota) belong to a group of saxicolous lichens with brown to black foliose thalli, which have recently undergone extensive changes in circumscription. Taxa belonging to Parmeliaceae are prolific producers of bioactive compounds, which have also been traditionally used for chemotaxonomic purposes. However, the chemical diversity of the genus Melanelia and the use of chemical data for species discrimination in this genus are largely unexplored. In addition, identification based on morphological characters is challenging due to few taxonomically informative characters. Molecular identification methods, such as DNA barcoding, have rarely been applied to this genus. This study aimed to identify the Melanelia species from Iceland using DNA barcoding approach, and to explore their chemical diversity using chemical profiling. Chemometric tools were used to see if lichen metabolite profiles determined by LC-MS could be used for the identification of Icelandic Melanelia species. Barcoding using the fungal nuclear ribosomal internal transcribed spacer region (nrITS) successfully identified three Melalenlia species occurring in Iceland, together with Montanelia disjuncta (Basionym: Melanelia disjuncta). All species formed monophyletic clades in the neighbor-joining nrITS gene tree. However, high intraspecific genetic distance of M. stygia suggests the potential of unrecognized species lineages. Principal component analysis (PCA) of metabolite data gave a holistic overview showing that M. hepatizon and M. disjuncta were distinct from the rest, without the power to separate M. agnata and M. stygia due to their chemical similarity. Orthogonal partial least–squares to latent structures–discriminate analysis (OPLS-DA), however, successfully distinguished M. agnata and M. stygia by identifying statistically significant metabolites, which lead to class differentiation. This work has demonstrated the potential of DNA barcoding, chemical profiling and chemometrics in identification of Melanelia species.

Chemotype variations among lichen ecotypes of Umbilicaria aprina as revealed by LC-ESI-MS/MS: a survey of antioxidant phenolics

“…These MS 2 ions are correspondent to those of stictic acid, therefore peak 2 was identified as the stictic acid, which is a depsidone. Our proposed fragmentation pattern for stictic acid in Fig 4 does not conform well to findings from other studies (Kumar et al, 2018;Matteucci et al, 2017;Parrot et al, 2013;Salgado et al, 2018;Torres-Benítez et al, 2017;Xu et al, 2017). Generally, after CO2 separation from the molecular ion ([M-H]= 385.419), a fragment will appear at m/z 341.07 whose cleavage results in the production of 2 fragments at m/z 148.932 and 196.04.…”

Microbial Communities of Cladonia Lichens and Their Biosynthetic Gene Clusters Potentially Encoding Natural Products

“…Atranorin was already fragmented in the ion source; therefore, fragment ions m / z 179.03389 (C 9 H 7 O 4 + ) and m / z 163.04007 (C 9 H 7 O 3 − ) were used for identification. Identification of perlatoric acid [ 64 ], rangiformic acid [ 65 ], and 4-O-methylolivetoric acid [ 66 ] were confirmed in reference to data presented in the cited publications.…”

Species in lichen-forming fungi: balancing between conceptual and practical considerations, and between phenotype and phylogenomics

“…The barcoding gap has also been used as an approach to delimit species, including lichen-forming fungi (Del Prado et al 2011;Puillandre et al 2012;Xu et al 2017). It is conceptually related to single-marker quantitative species delimitation such as GMYC, in that it assesses variational discontinuities in branch lengths.…”