How useful is the current species recognition concept for the determination of true morels? Insights from the Czech Republic

Abstract

The phylogentic diversity of the genus Morchella has only been sporadically studied in Central Europe. In this study, a molecular taxonomic revision of the Morchella species of the Czech Republic was performed using available fungarium specimens, fresh collections, and axenic cultures. Molecular phylogenetic analyses based on either ITS or five-locus (ITS, LSU, RPB1, RPB2, and EF-1α) sequencing and the application of principles of the genealogical concordance phylogenetic species recognition (GCPSR) have revealed the occurrence of 11 phylogenetic species in the region, but only six of them could be assigned unequivocally to the previously published phylospecies: Mel-3 (M.semilibera), Mel-10 (M.importuna), Mel-19 (M.eohespera), Mes-4 (M.americana), Mes-5 and Mes-8 (M.esculenta). One lineage was identified as a new phylospecies and is designated as Mel-39. Four lineages grouped together with two or more previously published phylospecies: Mel-13/26 (M.deliciosa), Mel-15/16 (M.angusticeps / M.eximioides), Mel-20/34 (M.purpurascens), and Mel-23/24/31/32 (M.pulchella). Our phylogenetic analyses and literature review shed light on the pitfalls of current molecular taxonomy of morels and highlight the ambiguities of present species recognition concepts. The main source of the problems seems to be rooted in the application of different methods (multigene vs single-gene sequencing, phenotypic determination) and approaches (monophyly vs paraphyly, the application or not of GCPSR, degree of differentiation between accepted species, etc.) by various authors for the delimitation of new phylospecies. Therefore, we propose five criteria for distinguishing new phylospecies in the genus Morchella based on molecular data, and recommend a more conservative approach in species delimitation.

DNA Barcoding and Species Classification of Morchella

“…In our study, the nuclear ITS region showed the highest intraspecific and interspecific divergences (0.00062 and 0.1347, respectively), as well as the highest species identification (44.44%) among the single candidate DNA barcodes. These results were largely consistent with previous studies on Morchella species [ 25 , 41 ]. Thus, we suggested that the ITS marker should be incorporated into the core barcode marker for Morchella species.…”

Has taxonomic vandalism gone too far? A case study, the rise of the pay-to-publish model and the pitfalls of Morchella systematics

“…In Morchella, the pitfalls of single-method approaches are exemplified by another recent study by Petrželová and Sochor (2019), focusing on molecular phylogenetics. While the authors of this study are correct to point out that many problems in the genus stem from the application of different methods of analysis and in some cases over-splitting, some of their proposals are unlikely to help.…”

“…While molecular phylogenetics have since clarified the species richness debate, early phylogenetic assessments were faced with the daunting task of matching the numerous phylogenetic clades (phylospecies) inferred through molecular tools to the several dozens of Linnaean binomials available, many of which type material were not available for or, if it existed, were too old to yield useful DNA data. To tackle this problem, the system of informal Mel/Mes designators for each phylospecies was introduced by Taşkın et al (2010) andO'Donnell et al (2011), and widely adopted in subsequent studies (Du et al 2012a, b;Pildain et al 2014;Richard et al 2015;Loizides et al 2016;Petrželová and Sochor 2019). This system, which used the prefix "Mel" for the /Elata clade and "Mes" for the /Esculenta clade followed by a serial number for each species, did not intend to replace binomial nomenclature (as falsely assumed by Phanpadith et al 2019), but was introduced as a temporary solution until the phylogenetic identity of early published binomials could be clarified.…”

“…However, several taxonomic issues remain to be resolved and systematic arrangements in the genus are still in flux. Much of the instability can be attributed to a number of problems, such as (i) the absence of a uniformly applied methodology in species delimitation; (ii) insufficient sampling efforts; (iii) a shortage of integrative taxonomical approaches; (iv) unresolved synonymies Section editor: Roland Kirschner and misapplied names; (v) occasional hybridization among species; (vi) poor or inaccurate morphological descriptions of taxa; (vii) a fragmented or incomplete understanding of their distributional patterns and ecological niches; (viii) lack of molecular data from early-described taxa; and (ix) lack of a common language in descriptive terminology (Du et al 2012b(Du et al , 2019a(Du et al , 2020Loizides et al 2015Loizides et al , 2016Loizides et al , 2021Loizides 2017;Clowez andMoreau 2018a, 2018b;Baroni et al 2018;Petrželová and Sochor 2019).…”

“…Besides this obvious urgency, the present review was initiated to also address other ongoing problems in Morchella, including opposing views with regard to the delimitation of species. These are, on one hand, expressed by multilocus approaches employing a "merging" method based on the concept introduced by O' Donnell et al (2011) and, on the other hand, by approaches advocating for strict application of Genealogical Concordance Phylogenetic Species Recognition (GCPSR) with polygenic differentiation as a prerequisite, as recently proposed by Petrželová and Sochor (2019). In an effort to stabilize taxonomy within the genus, the current pitfalls in Morchella systematics are here further debated and a unified methodology for the circumscription of taxa, including a glossary of descriptive terminology, is proposed.…”