Species Delimitation in Taxonomically Difficult Fungi: The Case of Hymenogaster

Abstract

BackgroundFalse truffles are ecologically important as mycorrhizal partners of trees and evolutionarily highly interesting as the result of a shift from epigeous mushroom-like to underground fruiting bodies. Since its first description by Vittadini in 1831, inappropriate species concepts in the highly diverse false truffle genus Hymenogaster has led to continued confusion, caused by a large variety of prevailing taxonomical opinions.MethodologyIn this study, we reconsidered the species delimitations in Hymenogaster based on a comprehensive collection of Central European taxa comprising more than 140 fruiting bodies from 20 years of field work. The ITS rDNA sequence dataset was subjected to phylogenetic analysis as well as clustering optimization using OPTSIL software.ConclusionsAmong distinct species concepts from the literature used to create reference partitions for clustering optimization, the broadest concept resulted in the highest agreement with the ITS data. Our results indicate a highly variable morphology of H. citrinus and H. griseus, most likely linked to environmental influences on the phenology (maturity, habitat, soil type and growing season). In particular, taxa described in the 19th century frequently appear as conspecific. Conversely, H. niveus appears as species complex comprising seven cryptic species with almost identical macro- and micromorphology. H. intermedius and H. huthii are described as novel species, each of which with a distinct morphology intermediate between two species complexes. A revised taxonomy for one of the most taxonomically difficult genera of Basidiomycetes is proposed, including an updated identification key. The (semi-)automated selection among species concepts used here is of importance for the revision of taxonomically problematic organism groups in general.

Not as Ubiquitous as We Thought: Taxonomic Crypsis, Hidden Diversity and Cryptic Speciation in the Cosmopolitan Fungus Thelonectria discophora (Nectriaceae, Hypocreales, Ascomycota)

“…Given the lack of diagnostic morphological characters than can be used for taxonomic circumscription within many fungal groups and especially species complexes, the inclusion of other kinds of data such as molecular characters is extremely helpful for establishing species limits [21], [62], [63]. Our species delimitation criterion is the genealogical concordance phylogenetic species recognition (GCPSR) [19], which is based on the convergence of evidence from phylogenetic analyses of unlinked loci, combined with species tree recovery and genetic divergence estimates.…”

“…These are phenomena commonly seen at the family and genus levels; however, at the species level, many cases were cosmopolitanism has been assumed have been disproven by molecular data [5]. While some empirical studies have supported the Bass-Becking hypothesis in some species of microorganisms [6], [12]–[15], there are many examples, not only for the majority of fungi [2], [16]–[21], but also for other microbial eukaryotes, marine and fresh water invertebrates, and even for some protists [22]–[27], where this hypothesis has been disproven. Since the rise of molecular phylogenetics over two decades ago, the view that microorganisms have large-scale spatial distributional ranges has changed, mostly due to the use of molecular markers and phylogenetic analyses, which have increased the level of resolution in systematics studies [2].…”

Diversity of Termitomyces Associated with Fungus-Farming Termites Assessed by Cultural and Culture-Independent Methods

“…PCR reactions were performed using TaKaRa Ex Taq™ HS (TaKaRa Bio Inc.) according to [25], however, primers and annealing temperatures were different. The mitochondrial cytochrome oxidase II gene (COII) was amplified using a forward primer A-tLeu_mod (5′-CAG ATA AGT GCA TTG GAT TT-3′) and a reverse primer B-tLys (5′-GTT TAA GAG ACC AGT ACT TG-3′) [26], while the ITS rDNA gene was amplified using a Termitomyces- specific modified ITS primer (ITS1FT: 5′-GTT TTC AAC CAC CTG TGC AC-3′) and ITS4 [11], [27].…”

Phylogeny and phylogeography of the Tuber brumale aggr.

“…with HinfI was utilized earlier by Giomaro et al (2002) et al 2006;Bonuso et al 2009;Li et al 2010;Van de Putte et al 2010;Chen et al 2011;Stielow et al 2011;Sheedy et al 2013;Urban et al 2013). Furthermore, the assessment and protection of biodiversity require knowledge about species that are complicated to distinguish merely on morphological grounds.…”