An overview of the taxonomy, phylogeny, and typification of nectriaceous fungi in Cosmospora, Acremonium, Fusarium, Stilbella, and Volutella

A comprehensive phylogenetic reassessment of the ascomycete genus Cosmospora (Hypocreales, Nectriaceae) is undertaken using fresh isolates and historical strains, sequences of two protein encoding genes, the second largest subunit of RNA polymerase II (rpb2), and a new phylogenetic marker, the larger subunit of ATP citrate lyase (acl1). The result is an extensive revision of taxonomic concepts, typification, and nomenclatural details of many anamorph- and teleomorph-typified genera of the Nectriaceae, most notably Cosmospora and Fusarium. The combined phylogenetic analysis shows that the present concept of Fusarium is not monophyletic and that the genus divides into two large groups, one basal in the family, the other terminal, separated by a large group of species classified in genera such as Calonectria, Neonectria, and Volutella. All accepted genera received high statistical support in the phylogenetic analyses. Preliminary polythetic morphological descriptions are presented for each genus, providing details of perithecia, micro- and/or macro-conidial synanamorphs, cultural characters, and ecological traits. Eight species are included in our restricted concept of Cosmospora, two of which have previously documented teleomorphs and all of which have Acremonium-like microconidial anamorphs. A key is provided to the three anamorphic species recognised in Atractium, which is removed from synonymy with Fusarium and epitypified for two macroconidial synnematous species and one sporodochial species associated with waterlogged wood. Dialonectria is recognised as distinct from Cosmospora and two species with teleomorph, macroconidia and microconidia are accepted, including the new species D. ullevolea. Seven species, one with a known teleomorph, are classified in Fusicolla, formerly considered a synonym of Fusarium including members of the F. aquaeductuum and F. merismoides species complex, with several former varieties raised to species rank. Originally a section of Nectria, Macroconia is raised to generic rank for five species, all producing a teleomorph and macroconidial anamorph. A new species of the Verticillium-like anamorphic genus Mariannaea is described as M. samuelsii. Microcera is recognised as distinct from Fusarium and a key is included for four macroconidial species, that are usually parasites of scale insects, two of them with teleomorphs. The four accepted species of Stylonectria each produce a teleomorph and micro- and macroconidial synanamorphs. The Volutella species sampled fall into three clades. Pseudonectria is accepted for a perithecial and sporodochial species that occurs on Buxus. Volutella s. str. also includes perithecial and/or sporodochial species and is revised to include a synnematous species formerly included in Stilbella. The third Volutella-like clade remains unnamed. All fungi in this paper are named using a single name system that gives priority to the oldest generic names and species epithets, irrespective of whether they are originally based on anamorph or teleomorph structures. The rationale behind this is discussed

A revision of Cyanonectria and Geejayessia gen. nov., and related species with Fusarium-like anamorphs

A revision of Fusarium-like species associated with the plant genus Buxus led to a reconsideration of generic concepts in the Fusarium clade of the Nectriaceae. Phylogenetic analyses of the partial second largest subunit of the RNA polymerase II (rpb2) and the larger subunit of the ATP citrate lyase (acl1) gene exons confirm the existence of a clade, here called the terminal Fusarium clade, that includes genera such as Fusarium sensu stricto (including its Gibberella teleomorphs), Albonectria, Cyanonectria, “Haematonectria”, the newly described genus Geejayessia, and “Nectria” albida. Geejayessia accommodates five species. Four were previously classified in Nectria sensu lato, namely the black perithecial, KOH–species G. atrofusca and the orange or reddish, KOH+ G. cicatricum, G. desmazieri and G. zealandica. Geejayessia celtidicola is newly described. Following our phylogenetic analyses showing its close relationship with Cyanonectria cyanostoma, the former Gibbera buxi is recombined as the second species of Cyanonectria. A three gene phylogenetic analysis of multiple strains of each morphological species using translation elongation factor 1 α (tef-1), rpb2 and acl1 gene exons and introns confirms their status as distinct phylogenetic species. Internal transcribed spacer of the ribosomal RNA gene cluster and nuclear large ribosomal subunit sequences were generated as additional DNA barcodes for selected strains. The connection of Fusarium buxicola, often erroneously reported as the anamorph of G. desmazieri, with the bluish black and KOH+ perithecial species C. buxi is reinstated. Most Cyanonectria and Geejayessia species exhibit restricted host ranges on branches or twigs of Buxus species, Celtis occidentalis, or Staphylea trifolia. Their perithecia form caespitose clusters on well-developed, mostly erumpent stromata on the bark or outer cortex of the host and are relatively thin-walled, mostly smooth, and therefore reminiscent of the more or less astromatous, singly occurring perithecia of Cosmospora, Dialonectria, and Microcera. The cell walls in outer- and inner layers of the perithecial walls of Cyanonectria and Geejayessia have inconspicuous pore-like structures, as do representative species of Albonectria, Fusarium sensu stricto, “Haematonectria”, and “Nectria” albida. The taxonomic significance of these structures, which we call Samuels' pores, is discussed