The root-symbiotic Rhizoscyphus ericae aggregate and Hyaloscypha (Leotiomycetes) are congeneric: Phylogenetic and experimental evidence

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.

Evolution of apomixis loci in Pilosella and Hieracium (Asteraceae) inferred from the conservation of apomixis-linked markers in natural and experimental populations

The Hieracium and Pilosella (Lactuceae, Asteraceae) genera of closely related hawkweeds contain species with two different modes of gametophytic apomixis (asexual seed formation). Both genera contain polyploid species, and in wild populations, sexual and apomictic species co-exist. Apomixis is known to co-exist with sexuality in apomictic Pilosella individuals, however, apomictic Hieracium have been regarded as obligate apomicts. Here, a developmental analysis of apomixis within 16 Hieracium species revealed meiosis and megaspore tetrad formation in 1 to 7% of ovules, for the first time indicating residual sexuality in this genus. Molecular markers linked to the two independent, dominant loci LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP) controlling apomixis in Pilosella piloselloides subsp. praealta were screened across 20 phenotyped Hieracium individuals from natural populations, and 65 phenotyped Pilosella individuals from natural and experimental cross populations, to examine their conservation, inheritance and association with reproductive modes. All of the tested LOA and LOP-linked markers were absent in the 20 Hieracium samples irrespective of their reproductive mode. Within Pilosella, LOA and LOP-linked markers were essentially absent within the sexual plants, although they were not conserved in all apomictic individuals. Both loci appeared to be inherited independently, and evidence for additional genetic factors influencing quantitative expression of LOA and LOP was obtained. Collectively, these data suggest independent evolution of apomixis in Hieracium and Pilosella and are discussed with respect to current knowledge of the evolution of apomixis.

Reconstruction of phylogenetic relationships in a highly reticulate group with deep coalescence and recent speciation (Hieracium, Asteraceae)

Phylogeny reconstruction based on multiple unlinked markers is often hampered by incongruent gene trees, especially in closely related species complexes with high degrees of hybridization and polyploidy. To investigate the particular strengths and limitations of chloroplast DNA (cpDNA), low-copy nuclear and multicopy nuclear markers for elucidating the evolutionary history of such groups, we focus on Hieracium s.str., a predominantly apomictic genus combining the above-mentioned features. Sequences of the trnV-ndhC and trnT-trnL intergenic spacers were combined for phylogenetic analyses of cpDNA. Part of the highly variable gene for squalene synthase (sqs) was applied as a low-copy nuclear marker. Both gene trees were compared with previous results based on the multicopy external transcribed spacer (ETS) of the nuclear ribosomal DNA. The power of the different markers to detect hybridization varied, but they largely agreed on particular hybrid and allopolyploid origins. The same crown groups of species were recognizable in each dataset, but basal relationships were strongly incongruent among cpDNA, sqs and ETS trees. The ETS tree was considered as the best approximation of the species tree. Both cpDNA and sqs trees showed basal polytomies as well as merging or splitting of species groups of non-hybrid taxa. These patterns can be best explained by a rapid diversification of the genus with ancestral polymorphism and incomplete lineage sorting. A hypothetical scenario of Hieracium speciation based on all available (including non-molecular) evidence is depicted. Incorporation of seemingly contradictory information helped to better understand species origins and evolutionary patterns in this notoriously difficult agamic complex.

Conflicting character distribution within different data sets on cardueline finches: artifact or history?

Cardueline finches (Passeriformes: Fringillidae, Carduelinae) provide an example of unresolved species relationships despite decades of extensive study of the group. Existing morphological studies suffer from numerous cases of assumed parallel evolution due to a conflicting character distribution in different lineages. In this study, results of assumed parallel evolution due to a conflicting character distribution in different lineages. In this study, results of cytochrome b sequence analysis are compared with species relationships suggested by morphological and behavioral evidence. In the molecular analyses, species clusters mutually excluding each other were observed, lowering the statistical support of the internodes, i.e., the branches could not be resolved convincingly. Despite these difficulties, some phylogenetic signal was present in the molecular data as well as in the other approaches. In particular, any species or genus relationship suggested by cytochrome b sequence analysis was reflected by some other evidence. Based on this general congruence of the different data sets and on a considerable cytochrome b tree stability observed independent of species combination, choice of outgroup and tree-generating method, the short internodes are interpreted to reflect a historical reality. A model of cardueline evolution is proposed which assumes a population of cardueline ancestors with considerable polymorphism concerning the mitochondrial DNA and morphological characters alike. Retention of ancestral character states in different lineages and a subsequent rapid radiation are suggested to explain the conflicting character distributions observed in different fields of investigation.