Data mining for a phylogenetic study including the prominent ericoid mycorrhizal fungus Rhizoscyphus ericae revealed nearly identical ITS sequences of the bryophilous Hyaloscypha hepaticicola suggesting they are conspecific. Additional genetic markers and a broader taxonomic sampling furthermore suggested that the sexual Hyaloscypha and the asexual Meliniomyces may be congeneric. In order to further elucidate these issues, type strains of all species traditionally treated as members of the Rhizoscyphus ericae aggregate (REA) and related taxa were subjected to phylogenetic analyses based on ITS, nrLSU, mtSSU, and rpb2 markers to produce comparable datasets while an in vitro re-synthesis experiment was conducted to examine the root-symbiotic potential of H. hepaticicola in the Ericaceae. Phylogenetic evidence demonstrates that sterile root-associated Meliniomyces, sexual Hyaloscypha and Rhizoscyphus, based on R. ericae, are indeed congeneric. To this monophylum also belongs the phialidic dematiaceous hyphomycetes Cadophora finlandica and Chloridium paucisporum. We provide a taxonomic revision of the REA; Meliniomyces and Rhizoscyphus are reduced to synonymy under Hyaloscypha. Pseudaegerita, typified by P. corticalis, an asexual morph of H. spiralis which is a core member of Hyaloscypha, is also transferred to the synonymy of the latter genus. Hyaloscypha melinii is introduced as a new root-symbiotic species from Central Europe. Cadophora finlandica and C. paucisporum are confirmed conspecific, and four new combinations in Hyaloscypha are proposed. Based on phylogenetic analyses, some sexually reproducing species can be attributed to their asexual counterparts for the first time whereas the majority is so far known only in the sexual or asexual state. Hyaloscypha bicolor sporulating in vitro is reported for the first time. Surprisingly, the mycological and mycorrhizal sides of the same coin have never been formally associated, mainly because the sexual and asexual morphs of these fungi have been studied in isolation by different research communities. Evaluating all these aspects allowed us to stabilize the taxonomy of a widespread and ecologically well-studied group of root-associated fungi and to link their various life-styles including saprobes, bryophilous fungi, root endophytes as well as fungi forming ericoid mycorrhizae and ectomycorrhizae.

Thorough understanding of biodiversity is a fundamental prerequisite for biological research. A lack of taxonomic knowledge and species misidentifications are particularly critical for conservation. Here we present an example of Potamogeton floridanus, the Florida Pondweed, an endangered taxon endemic to a small area in the Florida panhandle, whose taxonomic status remained controversial for more than a century, and all previous attempts to elucidate its identity have failed. We applied molecular approaches to tackle the origin of the mysterious taxon and supplemented them with morphological and anatomical investigations of both historical herbarium collections and plants recently collected in the type area for a comprehensive taxonomic reassessment. Sequencing of two nuclear ribosomal markers and one chloroplast non-coding spacer resulted in the surprising discovery that P. floridanus is a hybrid of P. pulcher and P. oakesianus, with the former being the maternal parent. The hybrid colony is currently geographically isolated from the distribution range of P. oakesianus. We show that previous molecular analyses have failed to reveal its hybrid identity due to inadequate nuclear DNA sequence editing. This is an example how the uncritical use of automized sequence reads can hamper molecular species identifications and also affect phylogenetic tree construction and interpretation. This unique hybrid taxon, P. ×floridanus, adds another case study to the debate on hybrid protection; consequences for its conservation are discussed.

The family Potamogetonaceae has been taxonomically re-evaluated in Turkey, employing traditional morphological as well as molecular approaches (rbcL, ITS). Our fieldwork, herbarium studies and molecular analyses proved the existence of 22 taxa, of which 18 belong to Potamogeton (including 4 interspecific hybrids), 3 to Stuckenia and 1 to monotypic Groenlandia. Morphological re-descriptions of the recognized taxa were prepared, and the information concerning their distribution in Turkey was refined, based on plant material from extensive fieldwork and on specimens stored in herbaria that were previously not examined. Additionally, new identification keys to genera and species, and distribution maps of the species were prepared. Phylogenetic relationships and intraspecific variations were assessed by including samples from other regions. The status of the Zannichelliaceae was investigated using nuclear and chloroplast DNA markers. Our results from ITS sequence divergence corroborate the separation of the two families noted by some authors, and are in accordance with the substantial morphological differences between them. Relatively large genetic distance and non-monophyly indicate that two genotypes of P. gramineus constitute cryptic species, for which the Turkish localities expand upon the previously known distribution areas. We identified P. schweinfurthii as a new species for Turkey and report P. ×angustifolius for the first time for this country. Weak morphological differentiation and high sequence similarity did not permit reliable differentiation between the closely related Stuckenia amblyphylla and S. filiformis.

The widespread aquatic plant genus Callitriche is taxonomically very challenging, but noteworthy in many evolutionary aspects including a high overall diversity, extensive phenotypic plasticity, remarkable reproductive systems and a large variation in ploidy levels and chromosome numbers. We conducted a multi‐level systematic study on 346 individuals of 25 taxa from 21 mostly European countries. Flow cytometric estimation of genome size, chromosome counting and direct sequencing of ITS and trnT‐trnL DNA markers combined with RFLPs of the ITS region were applied in order to unravel the phylogenetic relationships among Callitriche taxa and to clarify the origin of polyploid species and hybrids. Additionally, ITS sequences from a recent worldwide phylogenetic study of the genus were included for comparison. We demonstrate that most of the traditionally recognized European Callitriche taxa are well defined by a combination of genome size and molecular markers. Several species showed remarkable intraspecific genetic variation; previously unknown cryptic taxa were revealed within C. stagnalis, C. truncata and North American C. heterophylla. The origin of selected polyploid taxa was investigated in detail. Diploid C. cophocarpa was confirmed to be the parental species of tetraploid C. platycarpa, but we did not find direct evidence for the putative allopolyploid origin of this species. The complex of C. brutia included three taxa; of these, C. hamulata is probably an allooctoploid derivative of C. brutia var. brutia and C. cophocarpa/C. platycarpa. The third member, C. brutia var. naftolskyi, was newly reclassified at the subspecies level; for the first time, chromosome numbers are provided for this poorly known taxon. For a single triploid sample, our results suggested an autopolyploid origin from C. stagnalis. Four Callitriche hybrids were revealed, two of which are newly described and validated here as C. ×nyrensis and C. brutia nothosubsp. neglecta. A tentative intrageneric concept of two sections (Callitriche, Pseudocallitriche) is adopted, with the need for a more detailed evaluation in the future.