Phylogenetic delimitation of Apiospora and Arthrinium.

In the present study six species of Arthrinium (including a new taxon, Ar. crenatum) are described and subjected to phylogenetic analysis. The analysis of ITS and 28S rDNA, as well as sequences of tef1 and tub2 exons suggests that Arthrinium s. str. and Apiospora represent independent lineages within Apiosporaceae. Morphologically, Arthrinium and Apiospora do not seem to have clear diagnostic features, although species of Arthrinium often produce variously shaped conidia (navicular, fusoid, curved, polygonal, rounded), while most species of Apiospora have rounded (face view) / lenticular (side view) conidia. Ecologically, most sequenced collections of Arthrinium were found on Cyperaceae or Juncaceae in temperate, cold or alpine habitats, while those of Apiospora were collected mainly on Poaceae (but also many other plant host families) in a wide range of habitats, including tropical and subtropical regions. A lectotype for Sphaeria apiospora (syn.: Ap. montagnei, type species of Apiospora) is selected among the original collections preserved at the PC fungarium, and the putative identity of this taxon, found on Poaceae in Mediterranean lowland habitats, is discussed. Fifty-five species of Arthrinium are combined to Apiospora, and a key to species of Arthrinium s. str. is provided. Citation: Pintos Á, Alvarado P (2021). Phylogenetic delimitation of Apiospora and Arthrinium. Fungal Systematics and Evolution 7: 197-221. doi: 10.3114/fuse.2021.07.10.

INTRODUCTION

The genus Arthrinium was proposed by Kunze & Schmidt (1817) and validated by Fries (1832) for Ar. caricicola, a species found on Carex (Cyperaceae) in Berlin (Germany) for which a lectotype (BPI 422608) and an epitype (CBS H-24083) were recently designated by Crous . Several other species of Arthrinium were found later in temperate, cold or alpine regions, mainly growing on Cyperaceae and Juncaceae hosts, but also Poaceae (Table 1). Most taxa were subsequently recollected, allowing researchers to confirm their distinct identity (Cooke 1954, Gjærum 1966, Scheuer 1996, Minter & Cannon 2018). Some of these species were relocated to different genera by Link (in Willdenow 1824) because of their different conidial shape, e.g., Camptoum (type species C. curvatum ≡ Ar. curvatum), Gonatosporium (type species G. puccinioides ≡ Ar. puccinioides), Goniosporium (type species G. puccinioides ≡ Ar. puccinioides), Sporophleum (type species S. gramineum = Ar. sporophleum). However, they were later again reduced to synonymy with Arthrinium because of their similar conidiophores and conidiogenesis (von Höhnel 1925, Cooke 1954). The type species of Tureenia, T. juncoidea, is considered a heterotypic synonym of Ar. cuspidatum, and therefore, Tureenia was also synonymized with Arthrinium (Cooke 1954).

Table 1.

Species of Arthrinium s. str. with the references containing the protologues, as well as the hosts and regions mentioned in the protologues.

Species	References	Host	Region
Ar. austriacum	Petrak (1959)	Carex (Cyperaceae)	Wienerwald, Austria
Ar. bicorne	Rostrup (1886)	Juncus (Juncaceae)	Kaafjord, Norway
Ar. caricicola	Kunze & Schmidt (1817)	Carex (Cyperaceae)	Berlin, Germany
Ar. carinatum	Bucholtz (1916)	Carex (Cyperaceae)	Saaremaa, Estonia
Ar. crenatum	Present study	(Poaceae), Carex (Cyperaceae)	Côte-d’Or, France
Ar. curvatum	Kunze & Schmidt (1823)	Scirpus (Cyperaceae)	Leipzig, Germany
Ar. cuspidatum	Cooke (1883), Tranzschel (1914)	Scirpus (Cyperaceae)	Mount Shasta, California, USA
Ar. fuckelii	Gjærum (1967)	Carex (Cyperaceae)	Norway
Ar. globosum	Koskela (1983)	Carex (Cyperaceae)	Oulu, Finland
Ar. japonicum	Pollack & Benjamin (1969), Yokoyama & Benjamin (1979)	Carex (Cyperaceae)	Aomori, Japan
Ar. juncoideum	Hall (1915), Saccardo (1931)	Juncus (Juncaceae)	Washington, USA
Ar. kamtschaticum	Elenkin (1914), Pollack & Benjamin (1969)	Carex (Cyperaceae)	Kamtchatka, Russia
Ar. lobatum	Ellis (1963)	(Poaceae)	Mucubají, Venezuela
Ar. luzulae	Ellis (1965)	Luzula (Juncaceae)	Switzerland
Ar. morthieri	Fuckel (1870)	Carex (Cyperaceae)	Dombresson, Switzerland
Ar. muelleri	Ellis (1976)	Carex (Cyperaceae)	Switzerland
Ar. naviculare	Rostrup (1886)	Carex (Cyperaceae)	Vasbottenfjaeld, Norway
Ar. puccinioides	Kunze & Schmidt (1823)	Carex (Cyperaceae)	Léman, France
Ar. sphaerospermum	Fuckel (1874)	Phleum (Poaceae)	Jura, France
Ar. sporophleoides	Fuckel (1874)	Carex (Cyperaceae)	Budenheim, Germany
Ar. sporophleum	Kunze & Schmidt (1823)	(Poaceae)	Grenznach, Germany
Ar. ushuvaiense	Speggazzini (1887)	Luzula (Juncaceae)	Tierra del Fuego, Argentina

Another large group of Arthrinium spp. occurs in a wide variety of climates (including tropical and subtropical regions) in association with Poaceae, as well as many other host plant families (including Cyperaceae and Juncaceae). The first species to be described in this group was probably Ar. saccharicola (Johnston & Stevenson 1917), which was found growing on Saccharum officinarum (Poaceae) in the coastal lowlands of Puerto Rico. Later, Subramanian (1956) combined another asexual species found on Saccharum officinarum, Microtypha saccharicola (type species of Microtypha), into Arthrinium, renaming it as Ar. spegazzinii. Ellis (1965) synonymized several other asexual genera with basauxic conidiogenesis under Arthrinium (Hughes 1953, Cole & Samson 1979, Minter 1985). One such genus, Papularia Fr. (actually an illegitimate name, non Papularia Forssk.), was considered the asexual morph of Apiospora (Saccardo 1875) by von Höhnel (1919), Petrak (1925) and Hudson (1960, 1963a). As a result, a biological relationship between Arthrinium and Apiospora was widely accepted after Ellis (1965). Other asexual genera synonymized with Arthrinium by Ellis (1965) included Innatospora (type species, I. rosea = Ar. arundinis sensu Ellis) and Pseudobasidium (type species P. bicolor = Ar. phaeospermum sensu Ellis). Samuels , showed a biological relationship between Apiospora and species of asexual genera such as Cordella (type species Cordella spinulosa), Pteroconium (type species P. asteroides = Ar. pterospermum sensu von Arx 1981), and Scyphospora (type species S. phyllostachydis = Ar. hysterinum, Sivanesan 1983, Kirk 1986), and hence these taxa were also considered as synonyms of Arthrinium. Due to these synonymies, multiple species occurring on European canes (Arundo, Phragmites — Poaceae) and Asian bamboo (Bambusa, Phyllostachys — Poaceae) were combined into Arthrinium (e.g. Ar. arundinis, Dyko & Sutton 1979), synonymized with other species of this genus (e.g. P. sphaerosperma (Pers.) Höhn = Ar. phaeospermum sensu Ellis 1965), or proposed as new (e.g. Ar. macrosporum, Liu ).

More recently, with the aid of genetic data, Apiospora and Arthrinium were placed in their own family Apiosporaceae (Hyde ), and finally, Crous & Groenewald (2013) synonymized them (with Arthrinium having priority) on the basis of the one fungus- one name policy (Hawksworth ). Crous & Groenewald (2013) also resolved the genetic identity of multiple species of Arthrinium (= Apiospora), analysing ex-type collections, and confirmed that most species occur in Poaceae hosts, although some were known from Amaranthaceae, Cyperaceae, Euphorbiaceae, Fagaeae, Juncaceae, Restionaceae, Vitaceae and even seaweeds. Later, Wang provided genetic evidence of Arthrinium (= Apiospora) records on Theaceae and Rosaceae, but observed that two species occurring on Carex spp. (Ar. japonicum and Ar. puccinioides, sequences produced by Goto et al. unpubl. data) formed a monophyletic clade apparently unrelated with the remaining taxa. Pintos published the first genetic data from the type species of Arthrinium, Ar. cariciola, and samples occurring on Carex and Juncus, identified by them as Ar. curvatum and Ar. sporophleum. These samples form a monophyletic clade with those identified as Ar. japonicum and Ar. puccinioides, distinct from all other sequences of Arthrinium (= Apiospora). The authors suggested that Arthrinium s. str. could actually be phylogenetically different from Apiospora, but considered that confirming the phylogeny of additional species was necessary before making a taxonomic decision on the issue.

In the present work, this task is accomplished. The taxonomic status of the lineage including Ar. caricicola is re-examined after producing genetic data from additional taxa occurring on Cyperaceae and Juncaceae occurring in temperate or cold regions. A lectotype for S. apiospora (≡ Ap. montagnei) is selected to fix the ecological concept of this species and its clade, while the taxonomic status of Arthrinium species is updated in accordance with the phylogenetic results obtained.

MATERIALS AND METHODS

Samples studied

To isolate sexual morphs, fresh mature ascomata were soaked in water for 2 h, and then placed in the base of a Petri-dish lid and covered with the inverted base containing 2 % water agar (WA) culture medium supplemented with 500 mg/L chloramphenicol. Inverted plates were incubated at room temperature for 24 h. Germinated ascospores in the culture medium were transferred to 2 % malt extract agar (MEA) plates (e.g. Crous ), which were incubated at room temperature. To isolate asexual morphs, conidia from colonies growing on the host were sampled with a sterilized needle and streaked over the surface of a Petri dish containing 2 % WA supplemented with 200 mg/L penicillin. The germinated conidia were then transferred to 2 % MEA plates and incubated at room temperature.

In addition to cultures obtained from fresh collections, several fungarium samples were retrieved from the public fungaria such as Cornell University (CUP, Ithaca, USA), Karl-Franzens-Universität Graz (GZU, Graz, Austria), Martin-Luther-Universitat (HAL, Halle, Germany), and Muséum National d’Histoire Naturelle (PC, Paris, France), as well as several private collections from Alain Gardiennet (AG), Ángel Pintos (AP), Edwin W. Johanssen (EWJ), and Volker Kummer (VK). Images and data from type specimens were also retrieved from the Farlow Fungarium (FH, Harvard University, USA), as well as the Conservatory and Botanical Garden of the City of Geneva (G, Geneva, Switzerland). Cultures were deposited at Westerdijk Fungal Biodiversity Institute (CBS, Utrecht, The Netherlands).

DNA isolation, amplification and phylogeny

Total DNA was extracted from cultured isolates and dried fungarium specimens employing a modified protocol based on Murray & Thompson (1980). Amplification reactions (Mullis & Faloona 1987) included 35 cycles with an annealing temperature of 54 ºC. Primers ITS1F and ITS4 (White , Gardes & Bruns 1993) were employed to amplify the ITS1-5.8S-ITS2 nrDNA region (ITS), while LR0R and LR5 (Vilgalys & Hester 1990, Cubeta ) were used for the 28S nrDNA region (LSU), EF1-728F, EF1-983F and EF1-1567R (Carbone & Kohn 1999, Rehner & Buckley 2005) for the translation elongation factor 1-alpha (tef1) gene, and T1, Bt2a, and Bt2b (Glass & Donaldson 1995; O’Donnell & Cigelnik 1997) for the β-tubulin gene (tub2). PCR products were checked in 1 % agarose gels, and positive reactions were sequenced with one or both PCR primers. Chromatograms were checked searching for putative reading errors in MEGA v. 5.0 (Tamura ), and these were corrected.

Two different sequence alignments were built (Table 2): 1) an alignment of 5.8S-ITS2 nrDNA, 28S nrDNA, as well as the tef1 exon between introns 1 and 2 (Stielow ), and the tub2 exon between introns 4 and 5, plus the 5’ region of the exon between introns 5 and 6, obtained from selected samples of Apiosporaceae and other related families of order Amphisphaeriales (using Triangularia verruculosa from order Sordariales as outgroup), and 2) an alignment of ITS1-5.8S-ITS2 nrDNA, 28S nrDNA, as well as 5’ extreme of the tef1 exon between introns 2 and 3, and tub2 introns 3–5 with the exons between them plus the 5’ extreme of the exon between introns 5 and 6, obtained from all samples of Arthrinium s. str. available in public databases (using Ap. tintinnabula ex-type as outgroup). BLAST (Altschul ) was used to select the most closely related sequences from the International Nucleotide Sequence Database Collaboration (INSDC, Cochrane ) public database, and UNITE (Nilsson ). The sequences employed (Supplementary Table S1) were mainly retrieved from Smith , Singh , Crous & Groenewald (2013), Crous , 2020), Senanayake , Dai , 2017), Wang , 2018), Jiang , 2019, 2020), Liu , Pintos , Yan , and Yang . Sequences first were aligned in MEGA software with its Clustal W application and then corrected manually. The number of sequences from each locus, as well as total sites and variable sites analyzed are reported in Table 2. ITS data were subjected to GBlocks v. 0.91b (Castresana 2000) to remove 71 ambiguously aligned positions from the alignment of Amphisphaeriales.

Table 2.

Partitions employed for phylogenetic analyses with the best fitting evolutionary model for each partition, as well as the number of variable sites, total sites and sequences analysed of each marker.

Partition	Model	Variable sites	Total sites	Sequences
Amphisphaeriales	–	541	1429	–
5.8S-ITS2 rDNA	GTR+G+I	132	281	149
28S rDNA	GTR+G+I	270	801	138
tef1 — exon between introns 1–2 /1st codon position	JC	58	138	91
tef1 — exon between introns 1–2 /2nd codon position	JC	58	138	91
tef1 — exon between introns 1–2 /3rd codon position	GTR+G	58	138	91
tub2 — 5’ of exons between introns 4–5 and 5–6 /1st codon position	JC+G	81	209	102
tub2 — 5’ of exons between introns 4–5 and 5–6 /2nd codon position	JC+G	81	209	102
tub2 — 5’ of exons between introns 4–5 and 5–6 /3rd codon position	GTR+G	81	209	102
Arthrinium s. str.	–	747	2436	–
ITS1-5.8S-ITS2 rDNA	GTR+G+I	157	477	44
28S rDNA	GTR+G+I	64	797	20
tef1 — 5’ of exon between introns 2–3 /1st codon position	JC	69	393	11
tef1 — 5’ of exon between introns 2–3 /2nd codon position	JC	69	393	11
tef1 — 5’ of exon between introns 2–3 /3rd codon position	GTR+G	69	393	11
tub2 — introns 3–5 with intermediate exons	GTR+G+I	424	620	20
tub2 — 5’ of exon between introns 5–6 /1st codon position	JC+G	33	149	19
tub2 — 5’ of exon between introns 5–6 /2nd codon position	JC+G	33	149	19
tub2 — 5’ of exon between introns 5–6 /3rd codon position	GTR+G	33	149	19

The aligned loci were loaded in PAUP v. 4.0b10 (Swofford 2003) and each partition was subjected to MrModeltest v. 2.3 (Nylander 2004) to select the best fitting evolutionary model for each partition (Table 2). GTR+G+I was selected for 5.8S-ITS2, LSU and tub2 introns, GTR+G for the 3rd codon positions of tef1 and tub2 exons, JC for tef1 1st and 2nd positions, and JC+G for tub2 exon 1st and 2nd positions. The concatenated dataset of each analysis was loaded in MrBayes v. 3.2.6 (Ronquist ), where a Bayesian analysis (BA) was performed (data partitioned as reported above with the best fitting model, two simultaneous runs, four chains, temperature set to 0.2, sampling every 100th generation) until convergence parameters were met after 9.05 M (Amphisphaeriales) and 1.28 M (Arthrinium s. str.) generations, standard deviation having fell below 0.005. RWTY (Warren ) was employed to estimate sample size (>200 ESS in all analyses), and select the proper burn in (first 2.5 M generations in Amphisphaeriales and 0.25 M in Arthrinium s. str.). Finally, a full search for the best-scoring maximum likelihood (ML) tree was performed in RAxML v. 8.2.12 (Stamatakis 2014) using the standard search algorithm (data partitioned as for BA, GTRCAT model for Amphisphaeriales, GTRGAMMA model for Arthrinium s. str., 2 000 bootstrap replications). Significance threshold was set above 0.95 for posterior probability (PP) and 70 % bootstrap proportions (BP). Separate alignments of 5.8-ITS2, LSU, tef1 exon and tub2 exon sequences of Apiosporaceae were subjected to independent BA analyses to check for congruence between these markers.

Morphology

Samples were studied with a Zeiss Axioscope compound microscope operating with differential interference contrast (DIC). Images were obtained with a FLIR camera using open-source software Microscopia Oberta (A. Coloma). Measurements were taken with FIJI win64 ImajeJ software, and reported as follows: maximum value in parentheses, range between the mean plus and minus the standard deviation, minimum value in parentheses, and the number of elements measured in parentheses. For some images of conidiophores, the image stacking software Zerene Stacker v. 1.04 (Zerene Systems LLC, Richland, WA, USA) was employed. Morphological descriptions were based on fertile cultures growing on 2 % MEA at room temperature. Scanning electron microscopy (SEM) images were taken with a Hitachi SU 5000 device with controlled pressure (Hitachi High-Technologies Europe, Germany) at the Centre de Microscopie INRAE/ Université de Bourgogne.

RESULTS

Phylogeny

The analysis of Apiosporaceae and related families in the order Amphisphaeriales based on 5.8S-ITS2, LSU, tef1 and tub2 exons (Fig. 1) revealed that samples of Arthrinium group in two significantly different clades, with the genus Nigrospora (type species Nigrospora panici) being the closest known relative. The three genetic clades form a monophyletic group, which is identified with the family Apiosporaceae. The existence of two different genetic clades containing species of Arthrinium was already noticed previously (Pintos ). One clade (Arthrinium s. str.) contains the type species of Arthrinium, Ar. caricicola (epitype CBS H-24083, Crous ), as well as other samples found growing on Cyperaceae, Juncaceae and Poaceae hosts in temperate, cold or alpine habitats, identified here as Ar. austriacum, Ar. luzulae, Ar. morthieri, Ar. puccinioides, Ar. sphaerospermum, Ar. cf. sporophleoides and Ar. sporophleum, as well as a new species described below. The other clade contains all sequenced samples of the sexual morph (identified as Ap. tintinnabula, Ap. sinense, Ap. montagnei, Ap. setosa, or Ap. bambusae = Ar. hysterinum), as well multiple samples of arthrinium-like species growing on Poaceae and other plant host families worldwide (including tropical and subtropical regions).

Fig. 1.

Majority rule consensus (50 %) ITS rDNA- 28S rDNA- tub2 exons- tef1 exons phylogram of the Amphisphaeriales obtained in MrBayes from 65 500 sampled trees. Nodes were annotated if supported by > 0.95 Bayesian PP (left) or > 70 % ML BP (right).

The separate analysis of ITS, LSU, and exon data from tef1 and tub2 genes from Apiosporaceae did not reveal any significant incongruence between these markers (data not shown). LSU alone is enough to discriminate the three genera of Apiosporaceae, while 5.8S-ITS2 provides significant support for Nigrospora and Arthrinium s. str. The tub2 exon sequences alone support a monophyletic origin of Nigrospora and Apiospora (but not Arthrinium), while the addition of data from intron 5 provides significant support for the three genera. Similarly, the short sequences analysed of tef1 exon between introns 1 and 2 (about 140 bp) support only Arthrinium s. str. (but not Apiospora or Nigrospora), while the analysis of the 5’ extreme of the tef1 exon between introns 2 and 3 (about 400 bp, available only from 22 samples of Arthrinium and Apiospora but not from Nigrospora), significantly supports an independent origin of these genera. Finally, tef1 intron 2 is apparently absent in all species of Apiospora (but present in both Arthrinium and Nigrospora), while tub2 intron 4 is apparently absent in Nigrospora (but present in Apiospora and Arthrinium).

The analysis of Arthrinium s. str. based on ITS and LSU, as well as the tef1 exon between introns 2 and 3 and tub2 data (introns 3–5 with intermediate exons, plus the 5’ extreme of exon between introns 5–6), revealed the existence of two significantly distinct major clades within this genus (Fig. 2). One of them contains the type species, Ar. caricicola, as well as two significantly supported groups, one including samples identified as Ar. japonicum, Ar. sporophleum and Ar. cf. sporophleoides, and the other containing samples identified as Ar. curvatum, Ar. luzulae and Ar. sphaerospermum, as well as several undetermined lineages. The other major clade contains samples identified as Ar. austriacum, Ar. morthieri, Ar. puccinioides (which has two significantly different, but apparently cryptic, genetic lineages), and a clade with two undetermined samples. The exact genetic boundaries of several species (e.g. Ar. luzulae, Ar. sphaerospermum, Ar. sporophleum) could not be resolved properly, probably due to the lack of complete data from the records in public databases.

Fig. 2.

Best scoring ITS rDNA- 28S rDNA- tub2- tef1 phylogram of the Apiosporaceae obtained in RAxML. Nodes were annotated if supported by > 0.95 Bayesian PP (left) or > 70 % ML BP (right). Non-significant support values are exceptionally represented inside parentheses.

On the basis of the genetic results outlined, the taxonomy of Arthrinium is revisited below. The genus Arthrinium is identified with the clade containing the type species, Ar. caricicola, and samples found in temperate, cold or alpine habitats. The clade containing samples of arthrinium-like species occurring worldwide (including tropical and subtropical habitats) is identified as Apiospora, and the species nested inside are therefore combined to this genus. The identity of the type species, Ap. montagnei, is discussed below, and a lectotype of its basionym, S. apiospora, selected among the original collections of this species maintained at PC. Species of Arthrinium sequenced for the first time in this study are re-described, and a new name is introduced for one of these lineages.

Taxonomy

Sacc, Atti Soc. Veneto-Trent. Sci. Nat. 4: 85. 1875.

Type species: Apiospora montagnei Sacc., Atti Soc. Veneto-Trent. Sci. Nat. 4: 85. 1875.

Sexual morph: Stromata forming black, linear, confluent, raised areas on host surface, with the longer axis broken at the apex revealing the ostioles of pseudothecia. Ascomata uniseriate or irregularly arranged beneath stromata, pseudothecial, black, globose to subglobose with a flattened base. Peridium composed of several layers of brown cells arranged in textura angularis, with a conspicuous periphysate ostiole. Hamathecium paraphyses hyaline, septate, deliquescing early. Asci unitunicate, broadly cylindrical, clavate or subglobose, pedicel indistinct, apically rounded. Ascospores apiosporic, clavate to fusoid with narrowly rounded ends, composed of a large upper cell and small lower cell, slightly curved, hyaline, smooth-walled, surrounded by a gelatinose sheath, with a large droplet at the centre of the upper cell.

Hyphomycetous asexual morph: Colonies compact, pulvinate, rounded, linear, effused becoming confluent, black. Mycelium partly superficial in young colonies, the superficial mycelium is hyaline, with age the cells turn brown, partly immersed in the substrate. Conidiophore mother cell formed densely from superficial hyphae, shape swollen, doliiform, subspherical, ovoid, barrel-shaped, flask-shaped, clavate or lageniform, hyaline to brown. Conidiophores basauxic, cylindrical, flexuous, unbranched, straight, hyaline, usually aseptate. Conidiogenous cells ampulliform to cylindrical, with tiny denticles, hyaline. Conidia in face view clavate, oval, elliptical, globose, subglobose, ellipsoid, subcylindrical, lobed, dentate or polygonal; in side view lenticular, with a pale equatorial slit; pale brown to brown, smooth to finely roughened, granular, or minutely guttulate. Sterile cells elongated, rolled up, lobed, flattened, hemispherical, usually bigger than conidia, brown. Setae present or absent erect, smooth, subcylindrical, tapering to the apex, septate, brown, intermingled among conidiophores.

Coelomycetous asexual morph: Conidiomata acervular, dark brown, partly immersed, becoming erumpent to superficial, parallel to the long axis of the host, opening by longitudinal splitting of the epidermis and revealing a black conidial mass. Conidiomata wall composed of several layers of dark brown to brown to hyaline cells arranged as textura angularis. Conidiophore mother cells arising in dense packs from a mat of brown hyphae emerging directly from the host, shape ranging from ampulliform to doliiform, lageniform, dome-shaped or cylindrical, hyaline to light brown, smooth, producing a single conidiophore. Conidiophores basauxic, strait to flexuous, verrucose or smooth, aseptate or with 1–2 septa. Conidiogenous cells hyaline, with tiny denticles. Conidia 1-celled, globose to obovoid, lenticular, elongated or ellipsoidal; dark brown, smooth-walled, with a thin longitudinal hyaline germ-slit, with a central scar at the base. Sterile cells gray, irregularly angled and lobed.

Notes: The name Apiospora Sacc. was considered confusingly similar to Apiosporium Kunze (type species Apiosporium salicis) by Kuntze (1891), who proposed Detonina as replacement name. The Art. 53.3 of the International Code of Nomenclature for fungi, algae, and plants (Turland ), does not specify the reasons for which two names should be considered confusing, other than being applied to related taxa (especially congeneric species) or commemorate the same person. The type species of Apiosporium, Apiosporium salicis, is currently thought to belong to Capnodiaceae (Dothideomycetes), as possible synonym of Capnodium salicinum (Chomnunti ). A proposal to preserve Capnodium over Apiosporium and other genera was already made, but rejected because of the lack of information from most types (Rogers 1950). Because of these reasons, Apiosporium can hardly be confused with Apiospora, and so the replacement name is here considered superfluous.

Morphologically, the sexual morphs of Apiospora (and the putative sexual morph of Arthrinium s. str., Pseudoguignardia scirpi = Ar. curvatum) have a large upper cell and a small basal cell. The sexual genera Scirrhiella and Rhabdostroma, each based on a different variety of Scirrhiella curvispora Speg., were synonymized with Apiospora by Rehm (1914) and von Höhnel (1919), respectively. These genera were characterised by their stromata, composed of compressed pseudothecia, but differed in their spore size. The sexual morph of the closely related genus Nigrospora, Khuskia (type species, K. oryzae = N. oryzae), also has stromata containing compressed pseudothecia, unitunicate asci surrounded by abundant septate paraphyses, and fusoid to curved unicellular ascospores that form a septum before germinating. Regarding the asexual morphs, those of Apiospora and Arthrinium s. str. have a basauxic conidiogenesis (Hughes 1953), but in Apiospora, conidia are generally more or less rounded in face view and lenticular in side view, while in Arthrinium, conidia are variously shaped (globose, angular, polygonal, curved, fusiform, navicular. However, there are some remarkable exceptions to these general trends among species of Apiospora, e.g. Ar. pterospermum (lobed or dentate conidia) or Ar. mytilomorphum (fusoid conidia), and those of Arthrinium, e.g. Ar. globosum and Ar. sphaerospermum (globose conidia). In addition, the conidiophores of several Arthrinium species have thick blackish septa, rarely observed in Apiospora (Ellis & Ellis 1951), while asexual morphs of Apiospora sometimes develop forming acervuli, a feature not observed yet in any species of Arthrinium. Finally, the asexual morph of the closely related genus Nigrospora usually has cylindrical or lenticular conidia, but lacks the characteristic basauxic conidiogenesis.

Regarding their ecology, Apiospora was first thought to be associated mainly with Poaceae (von Arx 1952, Müller & von Arx 1962), but the asexual morphs linked to this genus suggest a much wider host range (Ellis & Ellis 1951, Ellis 1965), including a species associated with Cyperaceae in the Southern Hemisphere (Ar. pterospermum, growing on Machaerina and Lepidosperma). Most sequenced collections of Arthrinium s. str. have been found associated with Cyperaceae and Juncaceae, and these hosts seem to be also the most frequent among samples of these species identified by previous authors (Ellis & Ellis 1951, Cooke 1954, Scheuer 1996, Minter & Cannon 2018). However, this seems to also be a loose association, as reports of Arthrinium s. str. from other plants (including Poaceae) are also known. Species of Apiospora have been found worldwide, from tropical and subtropical areas to Mediterranean, temperate and cold regions, while reports of Arthrinium s. str. from tropical and subtropical habitats are quite rare, and none of them has been confirmed yet. The closely related genus Nigrospora seems to be present in tropical regions associated with multiple host families, e.g. Brassicaceae, Ericaceae, Lauraceae, Musaceae, Poaceae, Rosaceae or Theaceae (Wang ).

Sacc., Atti Soc. Veneto-Trent. Sci. Nat. 4: 85. 1875. Fig. 3.

Fig. 3.

Apiospora montagnei (Montagne MC 5216, PC 0125160 lectotype of S. apiospora). A. Envelope at PC. B. Plant host (Arundo sp.) with stromata. C. Detail of stromata on host surface. D–F. Asci with ascospores. G–H. Ascospores. I. Asci and ascospores depicted in the protologue. Scale bars: C = 200 μm, D–H = 10 μm.

Synonyms: Sphaeria apiospora Durieu & Mont., Expl. Sci. Alg., Fl. Algér. 1, livr. 13: 492. 1849.

Hypopteris apiospora (Durieu & Mont.) Berk., Hooker’s J. Bot. Kew Gard. Misc. 6: 227. 1854.

Sexual morph: Stromata solitary to gregarious, immersed to erumpent, fusiform, with the long axis broken at the top by one or two cracks, 0.5–4 × 0.2–0.5 mm (n = 20). Ascomata uniseriate or irregularly arranged beneath stromata, pseudothecial, black, globose to subglobose with a flattened base, 150–200 μm high × 200–300 μm wide. Peridium composed of 5 or 6 layers of brown to hyaline cells arranged in textura angularis, with a conspicuous periphysate ostiole. Hamathecium paraphyses hyphae-like, up to 4 μm wide. Asci broadly cylindrical, clavate, with an indistinct pedicel, rounded at the apex, lacking apical apparatus, 72–115 × 14–18 μm. Ascospores uniseriate or biseriate, clavate to fusiform, straight or slightly curved, with narrowly rounded ends, composed of a large upper cell and a small lower cell, hyaline, smooth-walled, measuring 21–25 × 6–8 μm.

Specimens examined: Algeria, Algiers, undated, M.C. Durieu de Maisonneuve (PC FUSION91533); ibid. (PC FUSION91536); ibid. (PC FUSION91538); ibid. (PC FUSION91542); unknown locality, undated (Fungarium Montagne, PC FUSION91537); ibid. (Fungarium Montagne, PC FUSION91541). Algeria/France (mixed collection), Perpignan and Algiers, in culms of Arundo mauritanica, J.P.F.C. Montagne (Fungarium Montagne, PC MC5210). France, Perpignan, in culm of Arundo ‘mauritanica’, undated, J.P.F.C. Montagne, MC5216 (lectotype of Sphaeria apiospora designated here PC 0125160, MBT395682); ibid. MC5220 (PC).

Notes: The exact genetic identity of Ap. montagnei (a replacement name proposed to avoid creating a tautonym from the replaced synonym Sphaeria apiospora, Saccardo 1875) cannot be resolved yet, because there are multiple species with very similar sexual morphs, a problem found in many other species of Apiospora (Hudson ). Hudson (1960, 1963a) identified specimens found in Jamaica growing on Saccharum officinarum and Bambusa vulgaris as Ap. montagnei, and obtained an asexual morph identified as Papularia arundinis. This putative synonymy was largely followed after his works, despite that the host species were quite different from those mentioned in the original protologues. Bory de Saint-Vincent & Durieu de Maissoneuve (1849) reported that Sphaeria apiospora grows in culms of “Arundo mauritanica” near Perpignan (France) and the Bouzareah suburb of Algiers (Algeria), as well as on Piptatherum multiflorum plants in the Maison-Carrée suburb (currently known as El Harrach) of Algiers (Algeria). The host plant “Arundo mauritanica” should refer to Arundo mauritanica (Poiret 1789), later combined as Ampelodesmos mauritanicus (Durand & Schinz 1895), but most probably it refers to the illegitimate homonym Arundo mauritanica (Desfontaines 1798–1799), likely Arundo aff. plinii (Danin 2004). Poiret’s legitimate binomial Arundo mauritanica was at that time subsumed under Amp. tenax (Link 1827), a plant cited by Bory de Saint-Vincent & Durieu de Maisonneuve (1849) as host of other fungi, and Link’s approach is explicitly followed in a later work by Cosson & Durieu de Maisonneuve (1854). The host plants of the original collections from Perpignan stored at the Fungarium of Paris (PC) were checked, confirming that these were species of the genus Arundo, not Ampelodesmos. Hardion , 2014) conducted extensive genetic studies on Arundo aff. plinii populations and fungarium specimens, and concluded that three distinct lineages could be discriminated: Arundo plinii s. str. restricted to Italy, Croatia, Albania and Greece, A. micrantha with a circum-Mediterranean distribution, and A. donaciformis restricted to southern France and Italian Liguria. Specimens of A. micrantha and A. donaciformis have been collected near Narbonne, not far from one of the original collection sites of Sphaeria apiospora at Perpignan. Therefore, both species could have been the original host of this fungus.

Crous & Groenewald (2013) and Pintos provided a first insight of the genetic diversity of Apiospora (as Arthrinium) in the Mediterranean region, studying samples obtained from the original host genera reported for Ap. montagnei, Arundo and Piptatherum. At least three species, Ar. marii, Ar. phragmitis, and Ar. piptatheri were found in Piptatherum miliaceum, while another four, Ar. ibericum, Ar. italicum, Ar. marii and Ar. phragmitis were found in Arundo spp. Three out of these five species, Ar. ibericum, Ar. italicum and Ar. piptatheri, seem to be relatively rare, while the other two, Ar. marii and Ar. phragmitis are more or less widespread. Asci and ascospore size of the sexual morph of both species (Pintos ) are comparable with those observed in the lectotype collection of S. apiospora (≡ Ap. montagnei) from Perpignan chosen here (PC 0125160, MBT395682): asci 70–110 μm, ascospores 21–25 μm. These measurements are comparable also with those observed by Hyde in another sample collected by Durieu de Maisonneuve in Algeria (stored also at PC), which has ascospores 23–28 μm. Therefore, Ar. marii and Ar. phragmitis are, by now, the most probable matches of Ap. montagnei. However, additional samples from Arundo and Piptatherum plants growing near the type locality (Perpignan) are needed to confirm if other species occur in these hosts. The sequences identified as Ap. montagnei in public databases, e.g. ICMP 6967 (isolated from Bambusa sp. growing in New Zealand) or CBS 212.30 (from Phragmites australis growing in UK), do not seem to match any of the species found by Pintos in Arundo or Piptatherum, but this could be due to the incomplete data available from these collections. Putative heterotypic synonyms can be found in Müller & von Arx (1962) and Kirk (1991).

(Z.L. Luo et al.) Pintos & P. Alvarado, MycoBank MB837741.

Basionym: Arthrinium aquaticum Z.L. Luo et al., Fungal Diversity 1: 179. 2019.

(Corda) Pintos & P. Alvarado, MycoBank MB837742.

Basionym: Gymnosporium arundinis Corda, Icon. fung. 2: 1. 1838.

Synonyms: Papularia arundinis (Corda) Fr., Summa veg. Scand: 509. 1849.

Coniosporium arundinis (Corda) Sacc., Syll. fung. 3: 759. 1884.

Melanconium sphaerospermum subsp. arundinis (Corda) Grove, Bull. Misc. Inf. Kew: 173. 1918.

Arthrinium arundinis (Corda) Dyko & B. Sutton, Mycotaxon 8: 119. 1979.

(Calvo & Guarro) Pintos & P. Alvarado, MycoBank MB837675.

Basionym: Arthrinium aureum Calvo & Guarro, Trans. Brit. Mycol. Soc. 75: 156. 1980.

(Pintos & P. Alvarado) Pintos & P. Alvarado, MycoBank MB837665.

Basionym: Arthrinium balearicum Pintos & P. Alvarado, MycoKeys 49: 24. 2019.

(M. Wang et al.) Pintos & P. Alvarado, MycoBank MB837666.

Basionym: Arthrinium camelliae-sinensis M. Wang et al., MycoKeys 34: 11. 2018.

(Mapook & K.D Hyde) Pintos & P. Alvarado, MycoBank MB837667.

Basionym: Arthrinium chromolaenae Mapook & K.D. Hyde, Fungal Diversity 101: 138. 2020.

(Pintos & P. Alvarado) Pintos & P. Alvarado, MycoBank MB837668.

Basionym: Arthrinium descalsii Pintos & P. Alvarado, MycoKeys 49: 28. 2019.

(M. Wang & L. Cai) Pintos & P. Alvarado, MycoBank MB837669.

Basionym: Arthrinium dichotomanthi M. Wang & L. Cai, MycoKeys 34: 12. 2018.

(Pintos & P. Alvarado) Pintos & P. Alvarado, MycoBank MB837670.

Basionym: Arthrinium esporlense Pintos & P. Alvarado, MycoKeys 49: 30. 2019.

(C.M. Tian & N. Jiang) Pintos & P. Alvarado, MycoBank MB837671.

Basionym: Arthrinium gaoyouense C.M. Tian & N. Jiang, Fungal Syst. Evol. 2: 3. 2018.

(D.Q. Dai & H.B. Jiang) Pintos & P. Alvarado, MycoBank MB837672.

Basionym: Arthrinium garethjonesii D.Q. Dai & H.B. Jiang, Mycosphere 7: 1337. 2017.

(M. Wang & L. Cai) Pintos & P. Alvarado, MycoBank MB837673.

Basionym: Arthrinium guizhouense M. Wang & L. Cai, MycoKeys 34: 13. 2018.

(Larrondo & Calvo) Pintos & P. Alvarado, MycoBank MB837674.

Basionym: Arthrinium hispanicum Larrondo & Calvo, Mycologia 84: 476. 1992.

(Crous) Pintos & P. Alvarado, MycoBank MB837676.

Basionym: Arthrinium hydei Crous, IMA Fungus 4: 142. 2013.

(D.Q. Dai & K.D. Hyde) Pintos P. Alvarado, MycoBank MB837677.

Basionym: Arthrinium hyphopodii D.Q. Dai & K.D. Hyde, Fungal Diversity 73: 112. 2015.

(Sacc.) Pintos & P. Alvarado, MycoBank MB837743.

Basionym: Melanconium hysterinum Sacc., Bol. Soc. Broteriana 11: 27. 1893.

Synonyms: Scyphospora hysterina (Sacc.) Sivan., Trans. Brit. Mycol. Soc. 81: 331. 1983.

Arthrinium hysterinum (Sacc.) P.M. Kirk, Trans. Brit. Mycol. Soc. 86: 409. 1986.

(Pintos & P. Alvarado) Pintos & P. Alvarado, MycoBank MB837678.

Basionym: Arthrinium ibericum Pintos & P. Alvarado, MycoKeys 49: 34. 2019.

(Kajale et al.) Pintos P. Alvarado, MycoBank MB837744.

Basionym: Arthrinium intestini Kajale et al. (as ‘gutiae’), Persoonia 35: 315. 2105.

(Pintos & P. Alvarado) Pintos & P. Alvarado, MycoBank MB837679.

Basionym: Arthrinium italicum Pintos & P. Alvarado, MycoKeys 49: 36. 2019.

(R. Sharma et al.) Pintos & P. Alvarado, MycoBank MB837680.

Basionym: Arthrinium jatrophae R. Sharma et al., Fungal Diversity 55: 119. 2012.

(M. Wang & L. Cai) Pintos & P. Alvarado, MycoBank MB837681.

Basionym: Arthrinium jiangxiense M. Wang & L. Cai, MycoKeys 34: 14. 2018.

(Crous) Pintos & P. Alvarado, MycoBank MB837682.

Basionym: Arthrinium kogelbergense Crous, IMA Fungus 4: 143. 2013.

(F. Liu & L. Cai) Pintos & P. Alvarado, MycoBank MB837763

Basionym: Arthrinium locutum-pollinis F. Liu & L. Cai (as ‘locuta-pollinis’), Mycosphere 9: 1094. 2018.

(D.Q. Dai & K.D. Hyde) Pintos & P. Alvarado, MycoBank MB837683.

Basionym: Arthrinium longistromum D.Q. Dai & K.D. Hyde, Fungal Diversity 82: 62. 2016.

(Crous) Pintos & P. Alvarado, MycoBank MB837684.

Basionym: Arthrinium malaysianum Crous, IMA Fungus 4: 144. 2013.

(Larrondo & Calvo) Pintos & P. Alvarado, MycoBank MB837685.

Basionym: Arthrinium marii Larrondo & Calvo, Mycologia 82: 397. 1990.

(Larrondo & Calvo) Pintos & P. Alvarado, MycoBank MB837686.

Basionym: Arthrinium mediterranei Larrondo & Calvo, Mycologia 84: 476. 1992.

(Bhat & W.B. Kendrick) Pintos & P. Alvarado, MycoBank MB837762.

Basyonym: Arthrinium mytilomorphum Bhat & W.B. Kendrick, Mycotaxon 49: 24. 1993.

Pintos & P. Alvarado, MycoBank MB837756.

Synonym: Arthrinium bambusae M. Wang & L. Cai, MycoKeys 34: 10. 2018.

[to avoid homonymy with Apiospora bambusae (Turconi) Sivan., Trans. Brit. Mycol. Soc. 81: 331. 1983.]

Pintos & P. Alvarado, MycoBank MB837757.

Synonym: Arthrinium chinense C.M. Tian & N. Jiang, Sydowia 72: 78. 2020.

[to avoid homophony with Apiospora sinensis K.D. Hyde et al., Sydowia 50: 27. 1998.]

(D.Q. Dai & K.D. Hyde) Pintos & P. Alvarado, MycoBank MB837695.

Basionym: Arthrinium neogarethjonesii D.Q. Dai & K.D. Hyde, Mycosphere 11: 424. 2020.

(D.Q. Dai & H.B. Jiang) Pintos & P. Alvarado, MycoBank MB837696.

Basionym: Arthrinium neosubglobosum D.Q. Dai & H.B. Jiang, Mycosphere 7: 1337. 2017.

(M. Wang & L. Cai) Pintos & P. Alvarado, MycoBank MB837704.

Basionym: Arthrinium obovatum M. Wang & L. Cai, MycoKeys 34: 16. 2018.

(Crous) Pintos & P. Alvarado, MycoBank MB837703.

Basionym: Arthrinium ovatum Crous, IMA Fungus 4: 146. 2013.

(Senan. & K.D. Hyde) Pintos & P. Alvarado, MycoBank MB837705.

Basionym: Arthrinium paraphaeospermum Senan. & K.D. Hyde, Fungal Diversity 80: 198. 2016.

(Crous) Pintos & P. Alvarado, MycoBank MB837728.

Basionym: Arthrinium phragmitis Crous, IMA Fungus 4: 147. 2013.

(C.L. Yang et al.) Pintos & P. Alvarado, MycoBank MB837729.

Basionym: Arthrinium phyllostachydis C.L. Yang et al., Phytotaxa 406: 102. 2019.

(Pintos & P. Alvarado) Pintos & P. Alvarado, MycoBank MB837708.

Basionym: Arthrinium piptatherum Pintos & P. Alvarado, MycoKeys 49: 40. 2019.

(M. Wang & L. Cai) Pintos & P. Alvarado, MycoBank MB837707.

Basionym: Arthrinium pseudoparenchymaticum M. Wang & L. Cai, MycoKeys 34: 17. 2018.

(Crous) Pintos & P. Alvarado, MycoBank MB837709.

Basionym: Arthrinium pseudosinense Crous, IMA Fungus 4: 148. 2013.

(Crous) Pintos & P. Alvarado, MycoBank MB837710.

Basionym: Arthrinium pseudospegazzinii Crous, IMA Fungus 4: 149. 2013.

(Cooke & Massee) Pintos & P. Alvarado, MycoBank MB837711.

Basionym: Coniosporium pterospermum Cooke & Massee, Grevillea 19: 90. 1891.

Synonyms: Pteroconium pterospermum (Cooke & Massee) Grove, Hedwigia 55: 146. 1914.

Arthrinium pterospermum (Cooke & Massee) Arx, Gen. Fungi Spor. Pure Cult.: 331. 1981.

(C.M. Tian & N. Jiang) Pintos & P. Alvarado, MycoBank MB837712.

Basionym: Arthrinium qinlingense C.M. Tian & N. Jiang, Fungal Syst. Evol. 2: 5. 2018.

(Shiv M. Singh et al.) Pintos & P. Alvarado, MycoBank MB837716.

Basionym: Arthrinium rasikravindrae Shiv M. Singh et al., Mycotaxon 122: 452. 2013.

(Speg.) Pintos & P. Alvarado, MycoBank MB837731.

Basionym: Coniosporium sacchari Speg., Revta. Fac. Agron. Vet. Univ. Nac. La Plata 2: 248. 1896.

Synonym: Arthrinium sacchari (Speg.) M.B. Ellis, Mycol. Pap. 103: 11. 1965.

(F. Stevens) Pintos & P. Alvarado, MycoBank MB837732.

Basionym: Arthrinium saccharicola F. Stevens, J. Dept. Agric. Porto Rico 1: 223. 1917.

(Larrondo & Calvo) Pintos & P. Alvarado, MycoBank MB837733.

Basionym Arthrinium serenense Larrondo & Calvo, Mycologia 82: 396. 1990.

(H.B. Jiang et al.) Pintos & P. Alvarado, MycoBank MB837713.

Basionym: Arthrinium setostromum H.B. Jiang et al., Asian J. Mycol. 2: 260. 2019.

(Pers.) Pintos & P. Alvarado, MycoBank MB837962.

Basionym: Stilbospora sphaerosperma Pers., in Usteri Ann. Bot. 15: 31. 1795.

Synonyms: Melanconium sphaerospermum (Pers.) Link, in Willdenow Linn. Sp. Pl., 6(2): 91. 1825.

Papularia sphaerosperma (Pers.) Höhn., Sitzungsber. Kaiserl. Akad. Wiss. Wien. Math.-naturw. Kl., Abt. 1 125: 114. 1916.

Notes: Ellis (1965) considered Gymnosporium phaeospermum (found in pine wood) a synonym of the earlier species Stilbospora sphaerospora (found on tree bark) and Stilbospora sphaerosperma (found on Arundo and Phragmites). He probably used Corda’s name as basionym to combine this species into Arthrinium because of the putative homonymy of Persoon’s epithets with Ar. sphaerospermum Fuckel. Since Ar. sphaerospermum is a species of Arthrinium s. str., Persoon’s epithets are available again for Apiospora. However, the woody substrates where G. phaeospermum and S. sphaerospora were found do not fit well with the hosts of other species of Apiospora. Until further evidence is found, only Stilbospora sphaerosperma is combined into this genus. Saccardo (1884) reported that this species (as Melanconium sphaerospermum) has conidia 8–10 μm diam in face view, and 6–7 μm diam in side view. These measurements fit with the clade identified as Ar. phaeospermum sensu Ellis by Crous & Groenewald (2013), but the one identified as Ar. phragmitis could be another possible candidate. Type studies, and additional data from both lineages are needed to provide more informed conclusions.

(D.Q. Dai & K.D. Hyde) Pintos & P. Alvarado, MycoBank MB837715.

Basionym: Arthrinium subglobosum D.Q. Dai & K.D. Hyde, Fungal Diversity 73: 112. 2015.

(M. Wang & L. Cai) Pintos & P. Alvarado, MycoBank MB837734.

Basionym: Arthrinium subroseum M. Wang & L. Cai, MycoKeys 34: 18. 2018.

(D.Q. Dai & K.D. Hyde) Pintos & P. Alvarado, MycoBank MB837735.

Basionym: Arthrinium thailandicum D.Q. Dai & K.D. Hyde, Fungal Diversity 82: 66. 2016.

(Hol.-Jech.) Pintos & P. Alvarado, MycoBank MB837737.

Basionym: Nigrospora vietnamensis Hol.-Jech., Česká Mykol. 17: 19. 1963.

Synonym: Arthrinium vietnamense (Hol.-Jech.) Mei Wang & L. Cai, Persoonia 39: 139. 2017.

(Crous) Pintos & P. Alvarado, MycoBank MB837738.

Basionym: Arthrinium xenocordella Crous, IMA Fungus 4: 151. 2013.

(D.Q. Dai & K.D. Hyde) Pintos & P. Alvarado, MycoBank MB837739.

Basionym: Arthrinium yunnanum D.Q. Dai & K.D. Hyde, Fungal Diversity 82: 69. 2016.

Kunze & J.C. Schmidt, Mykol. Hefte 1: 9. 1817.

Type species: Arthrinium caricicola Kunze & J.C. Schmidt, Mykol. Hefte 1: 9. 1817.

Asexual morph. Colonies compact, pulvinate, round, effused becoming confluent, black. Mycelium partly superficial (hyaline in young specimens, turning brown with age), and partly immersed in the substratum. Conidiophore mother cells originating from superficial hyphae, forming a compact layer, swollen to doliiform, subspherical, ovoid, barrel-shaped, flask-shaped, clavate, or lageniform; hyaline to brown in colour. Conidiophores basauxic, cylindrical, flexuous, not branched, straight, hyaline, with brown to dark brown thick transverse septa. Conidiogenous cells hyaline, with tiny denticles. Conidia unicellular, lateral and sometimes also terminal, in face view variously shaped: polygonal to subglobose, curved, horn-like, flattened, oblong, fusiform, limoniform or lobate; with a distinct hyaline rim and sometimes also concentric rings; in side view hemispherical to triangular or conical; brown to dark brown. Sterile cells, terminal or subterminal (same location as conidia), often containing one or more highly refractive cubical bodies, globose to triangular, polygonal, hat-shaped, lobed, lageniform, curved, ellipsoidal or irregularly lobed; paler than conidia. Setae absent.

Notes: Sequenced samples of Arthrinium s. str. were mostly found on Cyperaceae and Juncaceae, but also Poaceae and other plant hosts. According to the compilation of published records made by Minter & Cannon (2018), Arthrinium species occur mainly in temperate, cold or alpine regions of the Northern Hemisphere, including Europe, Turkey, Iran, alpine India, Russia, China, Japan, Canada and the USA, as well as similar areas of the Southern Hemisphere (Argentina, South Africa, New Zealand). Samples found in subtropical and tropical regions could actually be different fungal species, e.g., reports of Ar. caricicola from Maharashtra, India (Hande ) might be Ap. mytilomorpha, described from the neighbouring state of Karnataka, since the latter species has fusoid conidia that could resemble the navicular conidia of Ar. caricicola. The reports of Ar. sphaerospermum in Minter & Cannon (2018) probably represent Ap. sphaerosperma (= Ar. phaeospermum sensu Crous & Groenewald 2013).

Petr., : 4. 1959. Fig. 4.

Fig. 4.

Arthrinium austriacum (GZU 000345006). A. Conidiophore mother cells. B. Conidiophore mother cell and conidiophore with conidia and sterile cells. C. Conidiophore with conidia. D–F. Conidia in side view. G. Sterile cell with cubical body. H. Conidia in face view. I. Envelope at GZU. Scale bars = 5 μm.

Asexual morph: Colonies punctiform, pulvinate to effuse, sometimes confluent, black, 80–220 (–250) μm diam. Mycelium with immersed and superficial layers composed of hyaline to very pale brown, branched and septate hyphae measuring 1.5–5 μm wide. Conidiophore mother cells spherical to ampulliform, 4–6 μm diam, attached to the superficial mycelium network by an irregularly shaped basal cell 2–4 μm diam. Conidiophores cylindrical, erect or flexuous, 40–100 μm long, with dark refringent septa. Conidiogenous cells hyaline, with inconspicuous denticles between septa. Conidia brownish, with two paler concentric rings, in face view irregularly polygonal or rounded and 9–12 μm diam, in side view irregularly triangular or polygonal and 10–14 × 8–10 μm. Sterile cells smaller and paler than conidia, globose to ellipsoid, containing large refringent crystalline granules.

Specimens examined: Austria, Lower Austria, Wienerwald, eastern foot of the Wienerberg, near Untertullnerbach, on Carex pendula, 23 Feb. 1998, Th. Barta (GZU 000345006); Styria, Koralpe, Deutschlandsberger Laßnitz Klause, on Carex pendula, 14 Aug. 1996, M. Heftberger (GZU 000345004); Upper Austria, Sankt Georgen im Attergau, ca. 13 km SSW of Vöcklabruck, E of Weyregg am Attersee, on Carex pendula, 7 Jul. 2002, H. Teppner (GZU 000345007).

Notes: The samples analysed in the present study were identified by Scheuer (1996), who compared them with the type material of Ar. austriacum [Austria, Lower Austria, Georgenberg near Purkersdorf, on Carex pendula, Oct. 1943, F. Von Petrak (holotype W)]. Arthrinium austriacum is characterised by the concentric rings of its conidia observed in face view. These rings are present also in Ar. puccinioides, but this species has regularly polygonal (never rounded) conidia in face view. In side view, conidia of Ar. austriacum resemble those of Ar. fuckelii and Ar. morthieri due to their irregularly triangular or polygonal morphology, but Ar. morthieri has oblong or irregular conidia in face view.

Pintos, P. Alvarado & Gardiennet, MycoBank MB837755. Fig. 5.

Fig. 5.

Arthrinium crenatum (AG19066). A. Host. B. Colony on host surface. C. Conidiophore mother cell. D. Conidia in side view. E–F. Colony growing on MEA. G–H Conidia and sterile cells attached to the conidiophore. I. Conidia in face view. J. Conidia observed with SEM. Scale bars: B = 200 μm, C–D, G–H = 5 μm, I = 10 μm.

Etymology: From ‘crena’ (Lat. incision, notch), referring to the morphology of conidia in face view, looking like a toothed gear.

Asexual morph with colonies compact, scattered, rounded to elongated, 500–1 100 × 200–500 μm (length × width, n = 10). Mycelium superficial and immersed, composed of hyaline to brown, smooth septate hyphae that branch and anastomose, measuring 2–5 μm diam. Conidiophore mother cells ampulliform to lageniform, measuring 5–9 × 4–6 μm (length × width) (n = 20), emerging from a network of hyaline to brown cells. Conidiophores cylindrical, straight or flexuous, septate, hyaline excepting for the brown or dark brown thick transverse septa, 25–100 × 2–4 μm (length × width) (n = 30), each segment measuring 9–11 μm long. Conidiogenous cells cylindrical, 1–3 × 1 μm, occurring between the septa of conidiophores. Conidia dark brown, smooth, in face view crenate or stellate, looking like a toothed wheel or a sprocket, 10–12 μm in diam., in side view polygonal, hemispherical, with wavy-stellate margin and convex apex, 7–9(–10) × 10–13 (height × width, n = 50). Sterile cells spherical to subspherical, with a cubic refringent element 7–10 μm in diam. Culture characteristics (day/light 25 °C, after 2 wk): colonies slow-growing, with sparse aerial mycelium, reaching 12 mm in 2 wk. On MEA and PDA, pale salmon on surface, salmon in reverse.

Typus: France, Côte-d’Or, Brochon, Champ Sement, on dead leaves of grass (probably Festuca burgundiana), 28 Apr. 2019, A. Gardiennet (holotype AG19066); ex-type culture CBS 146353.

Additional specimens examined: France, Côte-d’Or, Brochon, Champ Sement, on dead leaves of Carex cf. humilis / halleriana, 9 Dec. 2014, A. Gardiennet (A. Gardiennet fungarium AG14223). Germany, Potsdam, Bornim, SE end of Hugstraße, on leaves of Carex ciliata, 29 Sep. 2011, V. Kummer (V. Kummer fungarium VK-P-2529/19b).

Notes: Morphologically, the crenate conidia of Ar. crenatum resemble those of Ap. pterosperma, but the latter are 12–25 μm diam in face view and have more pointed lobes, while conidia of Ar. crenatum are only 10–12 μm diam, and have more rounded lobes. In addition, Ap. pterosperma lacks sterile cells. Apiospora pterosperma is known to occur on the Cyperaceae genera Machaerina and Lepidosperma, therefore representing an exception to the overall ecological preferences of Apiospora.

Kunze, Mykol. Hefte 2: 103. 1823. Fig. 6.

Fig. 6.

Arthrinium curvatum. A–F. (HAL 3337 F). A. Envelope at HAL. B. Copy of the original label. C. Colony on host (Scirpus sylvaticus). D–F. Conidia. G–K. (AG19036). G. Conidiophore mother cell. H. Conidia attached to conidiophore. I. Conidiogenous cell giving rise to conidia. J–K. Colony growing on MEA. Scale bars = 5 μm.

Synonym: Camptoum curvatum (Kunze) Link, in Willdenow Linn. Sp. Pl. 6(1): 44. 1824.

Colonies compact, round, often confluent, dark grey to black, 80–520 diam. Mycelium superficial and immersed, composed of hyaline to pale brown smooth hyphae 3–7 μm in diam. Conidiophore mother cells emerging from superficial hyphae, spherical to lageniform, hyaline with brown pigments at the base, measuring (3–)5–7(–8) × (3–)5–6(–8) μm (n = 30). Conidiophores cylindrical, not branched, straight or flexuous, hyaline, smooth, with a single brown transversal septum, measuring 30–100 × 2–4 μm (n = 30). Conidiogenous cells cylindrical, measuring 1–1.5 × 1–1.5 μm (n = 20). Conidia produced along the sides of conidiophores from well-developed denticles, strongly curved and rounded at the ends, brown coloured with a hyaline germ slit and a conspicuous scar, measuring (9–)11–14(–15) μm long in face view, (5–)6–8(– 9) μm in side view (n = 30). Sterile cells oblate or rounded, paler than conidia, not containing refringent bodies, 7–8 μm diam.

Culture characteristics: Flat colonies on MEA with moderate aerial mycelium, reverse whitish.

Typus: Germany, Saxony, Leipzig, on dead leaves of Scyrpus sylvaticus (holotype HAL 3337F).

Additional specimens examined: France, Auvergne, Puy-de-Dôme, Saint-Alyre-d’Arlanc, Le mouline de Chelles, on dead leaves of Scirpus sylvaticus, 855 m asl, 22 Apr. 2019, A. Gardiennet (Alain Gardiennet fungarium AG191036), culture CBS 146354; Calvados, Louvières, on dead leaves of Carex pendula, 18 Jan. 2020, A. Gardiennet, (Alain Gardiennet fungarium P301119A). Norway, Oslo, Wyllerløypa, grassy roadside, on leaves of Calamagrostis sp., 15 Apr. 2020, E.W. Johanssen (Edwin W. Johanssen fungarium EWJ24118299); ibid., in a moist slope between a stream and melting water near a ski slope, on leaves of Calamagrostis sp., 15 Apr. 2020, E.W. Johanssen, (Edwin W. Johanssen fungarium EWJ24117931). : Austria, Upper Austria, a bit W of Steyr, Schloss Rosenegg, on dead leaves of Carex cf. elata, 300 m asl, 9 Apr. 1982, C. Scheuer (GZU 000345023).

Notes: The samples identified here as Arthrinium curvatum var. curvatum are identical with the original collection studied (HAL 3337 F), and fit the descriptions made by Ellis & Ellis (1951), Scheuer (1996) and Minter & Cannon (2018). The new specimens were found in both Cyperaceae (Carex) and Poaceae (Calamagrostis) hosts, where the putatively related species Ar. luzulae and Ar. sphaerospermum are thought to occur too (Minter & Cannon 2018). Several undetermined sequences related to those of Ar. curvatum have been obtained from very different sources, including Oxytropsis kansuensis (Fabaceae), Festuca thurberi and Poa pratensis (Poaceae), Pinus contorta (Pinaceae) and Populus tremula (Salicaceae). Therefore, it seems that the whole clade is associated with a diverse range of host plants. Interestingly, Ar. curvatum is supposed to be the only species of Arthrinium s. str. from which a sexual morph has been obtained. The sexual morph was obtained by Gutner (1927) on Scirpus sylvaticus, and named Pseudoguignardia scirpi. Ellis & Ellis (1951) reproduced the experiment with a new variety, Ar. curvatum var. minus, but further studies on the life cycle of species of Arthrinium are needed to understand which hosts (if any) can actually develop a sexual morph of Arthrinium s. str. Arthrinium curvatum var. minus was proposed for specimens presenting curved spores smaller than those of Ar. curvatum var. curvatum. Minter & Cannon (2018) upgraded this variety to species rank as Ar. minus, due to the significant differences between the spore sizes of both varieties, which do not overlap. However, in the present work, specimens of both varieties (AG191036 and AP25418), did not show significant differences in up to three genetic markers (ITS, LSU, tub2), and so they are considered the same species until further evidence of reproductive isolation is found.

M.B. Ellis, Mycol. Pap. 103: 18. 1965. Fig. 7.

Fig. 7.

Arthrinium luzulae (AP7619.4.1). A. Colony on host surface. B–C. Conidia attached to conidiophore. D. Conidia in face view. E. Aberrant conidia in MEA culture. F–G. Colony growing on MEA. Scale bars: A = 200 μm, B–E = 5 μm.

Colonies punctiform, sometimes confluent, effuse, blackish brown to black, 100–400 μm diam. Mycelium superficial and also immersed in the substratum; superficial part composed of smooth-walled, pale to olivaceous brown septate hyphae 2–7 μm thick, branching and anastomosing; immersed part sparse, composed of pale olivaceous brown hyphae 1–4 μm thick. Conidiophore mother cells emerging on the mat formed by superficial hyphae, barrel-shaped to lageniform, measuring 4–8 × 3–6 μm. Conidiophores erect or erumpent, simple, cylindrical, straight or flexuose, sometimes branched, hyaline, 30–80 μm long and 3–6 μm diam, with multiple thick, brown to dark brown, transversal septa. Conidia curved with the ends bent inwards (horn-like), brown to dark brown, with a hyaline germ slit, smooth-walled, 16–21 × 11–15 μm in face view, 8–11 μm thick (side view), tapering at the ends of the horns to 2–4 μm. Sterile cells acrogenous, hemispherical, pale brown, 5–11 × 5–7 μm.

Culture characteristics: Flat colonies spreading on MEA with moderate aerial mycelium, reverse yellow.

Specimen examined: Spain, Catalonia, Girona, Coll de la Marrana, on dead leaves of Luzula sylvatica, 2 470 m asl, 7 Jun. 2019, Á. Pintos (Ángel Pintos fungarium AP7619-3), culture CBS 146356.

Notes: Arthrinium luzulae is the only species with inwardly curved conidia. The non-type specimen identified here matches the descriptions made by Ellis & Ellis (1951), Scheuer (1996) and Minter & Cannon (2018). Genetically, it is related to samples identified as Ar. curvatum (which have outwardly-curved conidia), suggesting that the whole clade containing these samples could have an ancestor with curved conidia (a feature not present in the other species of Arthrinium). Some samples inside this clade, here identified as Ar. sphaerospermum because of their globose conidia, could have reverted to an earlier undifferentiated conidial shape.

Fuckel, Fungi Rhen. Exs., Suppl. Fasc. 5: no. 1914. 1867. Fig. 8.

Fig. 8.

Arthrinium morthieri (GZU 000345043). A. Envelope at GZU. B,E–F. Conidia attached to conidiophore. C,G. Conidia in face view. D. Conidiophore mother cells. H. Sterile cell with cubical body. Scale bars = 5 μm.

Colonies pulvinate, rounded or ovoid, usually 100–300 μm diam, blackish brown in colour. Mycelium superficial and also immersed in the substratum, composed of branched and anastomosing, septate hyphae, pale to mid olivaceous brown, smooth-walled, 2–5 μm thick. Conidiophore mother cells emerging on the mat formed by superficial hyphae, subspherical or barrel-shaped, lageniform, 5–6 × 4–5 μm Conidiophores erect or ascending, simple, straight or flexuous, cylindrical, colourless except for the thick, brown to dark brown, transverse septa, smooth-walled, 30–90 μm long and 2–5 μm wide. Conidia flattened, oblong or irregularly rectangular to quadrangular or rhombic in face view, 11–16 × 5–9 μm, in side view triangular or rhombic, 11–16 × 11–16 μm, with a germ slit running along the outer wall. Sterile cells spherical to ellipsoidal, very pale, sometimes containing cubical refractive body 6–10 × 5–9 μm.

Specimens examined: Austria, Upper Austria, Steyr, a bit N of Schloss Rosenegg, 300 m asl, on Carex Pilosa, in an alluvial deciduous forest, 9 Jul. 1994, N. Vasilyeva & C. Scheuer (GZU 000345049); Wien, Leopoldsberg, ESE of Josefinenhütte, on Carex digitata, 6 Mar. 1998, Th. Barta (GZU 345043).

Notes: The samples analysed here were identified as Ar. morthieri by Scheuer (1996), and they match the descriptions provided by Ellis & Ellis (1951) and Minter & Cannon (2018). Their conidia resemble those of Ar. fuckelii, but the latter are about 15–21 × 5–8 μm in side view, vs. 11–16 × 11–16 μm in Ar. morthieri. In addition, sterile cells of Ar. morthieri lack lateral projections (present in Ar. fuckelii).

Fuckel, Jb. Nassau. Ver. Naturk. 27–28: 79. 1874. Fig. 9.

Fig. 9.

Arthrinium sphaerospermum (AP25619). A. Colony on host surface. B–D. Conidia attached to conidiophore. Scale bars: A = 200 μm, B–D = 5 μm.

Synonym: Goniosporium sphaerospermum (Fuckel) Sacc., Syll. Fung. 4: 280. 1886.

Colonies rounded to ovoid, pulvinate, up to 500 μm long, blackish brown. Mycelium superficial and also immersed in the substratum; superficial part composed of a network of septate, pale to mid brown, smooth-walled, hyphae, branched and anastomosing, measuring 2–7 μm thick, arranged in two or more layers; immersed hyphae pale to brown, 1–7 μm thick. Conidiophore mother cells emerging on the mat formed by superficial hyphae, subspherical to flask-shaped, measuring 5–9 × 4–8 μm Conidiophores erect or erumpent, simple, straight or flexuous, cylindrical, hyaline excepting for the thick, brown to dark brown, transversal septa, smooth-walled, 10–90 μm long and 2–3 μm wide. Conidia very densely packed in the conidiophore, globose or subglobose, dark gold to gold-brown in colour, smooth-walled, 6–9 μm diam. Sterile cells only seen in culture, cylindrical to oblong or clavate, paler than conidia, measuring 12–30 × 5–8 μm.

Typus: France, Jura, on Phleum pratensis, Apr. 1872, P. Morthier (holotype G 00127277).

Culture characteristics (day/light 25 °C, after 2 wk): Colonies slow-growing, with sparse aerial mycelium, reaching 30 mm in 2 wk. On MEA and PDA, white on surface, salmon in reverse.

Additional specimen examined: Norway, Viken, Akerhus, Nittedal, Varingskollen, alpine hill with some snow spots, probably on Poaceae, 27 May 2019, S. Moen (Ángel Pintos fungarium AP25619), culture CBS 146355.

Notes: The Norwegian sample identified here as Ar. sphaerospermum was compared with the type collection from France (G 00127277). Koskela (1983) reported that conidia of Ar. globosum and Ar. sphaerospermum look similarly globose in face view and ellipsoid in side view, but those of Ar. globosum have a hyaline rim not observed in Ar. sphaerospermum. Conidia of Ar. globosum are also slightly larger (8–10 μm) than those of Ar. sphaerospermum (6–8 μm). In addition, Ar. globosum is supposed to be strictly associated to Cyperaceae, while Ar. sphaerospermum has been found also in Poaceae, in the same way as the samples identified here as Ar. curvatum. Unfortunately, the original collections of Ar. globosum from Koskela could not be located in the OULU fungarium, and so the exact genetic identity of this species remains unresolved.

Fuckel, Jb. Nassau. Ver. Naturk. 27–28: 78. 1874. Fig. 10.

Fig. 10.

Arthrinium cf. sporophleoides (GZU 000345112). A. Colony on host surface. B. Conidiophore mother cell. C–D. Conidia attached to conidiophore with crenate sterile cells. E. Conidia. Scale bars: A = 200 μm, C–E = 5 μm.

Colonies compact, rounded to elongated, scattered or sometimes confluent, up to 600 μm diam. Mycelium superficial and also immersed, hyaline to pale brown, composed of smooth hyphae 3–7 μm diam. Conidiophore mother cells emerging on the mat formed by superficial hyphae, globose to lageniform, hyaline with brown pigments at the base, measuring 4–8 × 4–9 μm. Conidiophores erect or erumpent, simple, straight or flexuous, cylindrical, measuring 30–100 μm long and 2–5 μm wide, hyaline excepting for numerous brown to dark brown thick transversal septa. Conidia fusoid in face view, measuring 11–14 × 5–5.5 μm, in side view often triangular or polygonal with a distinct hyaline rim. Sterile cells irregularly lobed or subspherical with cubical refringent bodies.

Specimen examined: Austria, Styria, Ennstal, Gesäuse, Hartelsgraben, on Carex firma, 15 Sep. 1989, P. Zwetko (GZU 000345102, as Ar. sporophleum).

Additional specimens examined: : , Brandenburg, Potsdam-Mittelmark, Werder (Havel), Phöben, Wachtelberg, on Carex ericetorum, 18 Apr. 1999, V. Kummer (Volker Kummer fungarium VK-P-2524/1); Potsdam, Sacrow, 0.5 km NE road to Kladow, on Carex ericetorum, 15 Apr. 2004, V. Kummer (Volker Kummer fungarium VK-P-2524/2). Russia Leningradskaya Oblast, Lodeinopol’ Skiy District, 51 km W of Lodéinoye Pole, Nizhnesvirsky nature reserve, Segezha forestry, near the river Svir, on Carex ericetorum, wintered leaves, 28 May 1990, V. Mel′nik, (GZU 000345013). Sweden, Torne lappmark, Jukkaskärvi, on Carex vaginata, 13 Jul. 1986, A. Nograsek (GZU 000343016). : Estonia, Saaremaa Island, near Kihelkonna, on dead leaves of Carex ericetorum, 1909, F. Bucholtz, (holotype FH Bucholtz 1757). : Austria, Styria, Hochschwab, Aflenzer Staritzen, ca. 16 km S of Mariazell, NW of Seebergsattel, top of Seeleiten, 1700 m asl, on Carex atrata, 21 Jun. 1984, J. Hafellner (GZU 000345025). Romania, Harghita, Ciuc depression, near Bălan, on Carex sempervirens, 1600–1700 m asl, 16 Aug. 1942, A. Boros (GZU 000345026). : Austria, Styria, Seetal Alps, Zirbitzkogel, on Carex foetida, 1900 m asl, 1959, H. Heske (GZU 000345126); Ibid. (GZU 000345136). : Finland, Lapponia, NW Enontekiö, N Kovddoskaisi, alpine meadow, ca. 800 m asl, 1 Jul. 1968, H. Roivainen (CUP 5683). : Austria, Lower Austria, S-slope of Hutberg by Grünbach, on dead twigs of Carex hordeistichos, 29 Jun. 1998, Th. Barta (GZU 000345072); Lower Austria, 4.5 km SSW of Hainburg an der Donau, WNW of Bundessportschule Spitzerberg, on Carex flacca, 180 m asl, 5 May 2009, Th. Barta (GZU 313371); Styria, Hochschwab, Aflenzer Staritzen, S-slope of Seeleiten, NW of Seebergsattel, on Carex sempervirens, 9 Jul. 1997, C. Scheuer (GZU 000345040, as Ar. morthieri); Styria, Schladminger Tauern, Kleinsölk-Obertal, Schwarzensee, on Carex rostrata, 5 Aug. 1984, C. Scheuer (GZU 000345065); Styria, Schladminger Tauern, Kleinsölk, S of Gröbming, on Carex rostrata, 19 Jul. 1986, C. Scheuer (GZU 000345068); Upper Austria, immediately W of Steyr, floodplains of Steyr at Rosenegg, on Carex flacca, 19 May 1996, C. Scheuer (GZU 000345081). Germany, Brandenburg, Potsdam, Bornim, on dead leaves of Carex humilis, Sep. 2011, V. Kummer (GZU 000345086). : Austria, Burgenland, Leithagebirge, on Carex hordeistichos, 31 Oct. 2010, Th. Barta (GZU 000345112); Carinthia, immediately W of Krumpendorf am Wörthersee, on Carex sp., 2 Nov. 1999, H. Riegler-Hager (GZU 000345119); Styria, Ennstal, Gesäuse Nationalpark, Hartelsgraben, on Carex firma, 15 Sep. 1989, P. Zwetko (GZU 000345102); Styria, ca. 8 km ESE of Leibnitz, Rabenhofteiche, ca. 2 km NE of St. Veit am Vogau, on Carex brizoides, 15 Apr. 1983, C. Scheuer (GZU 000345111); Styria, Graz, Lustbühel, on Carex brizoides, 6 November 1981, C. Scheuer (GZU 000345110); Styria, Spielfeld-Straß, Attemsmoor, on Carex sp., 8 Oct. 1986, P. Zwetko (GZU 000345097). France, Côte-d’Or, Fauverney, La Chassagne, on Carex flacca, 10 May 2019, A. Gardiennet (Alain Gardiennet fungarium AG19067). Germany, Brandenburg, Alt Schadow, Krieg, on Carex acutiformis, 18 Oct. 1998, V. Kummer (Volker Kummer fungarium VK-P-2553/11); Brandenburg, Alt Schadow, Raatschweg, on Carex riparia, 16 Jun. 2018, V. Kummer (Volker Kummer fungarium VK-P-3849/43); Brandenburg, Golßen, Zützen, on Carex acutiformis, 23 Oct. 2016, V. Kummer (Volker Kummer fungarium VK-P-4047/24); Brandenburg, Potsdam, Bornim, Pannenberg, on Carex humilis, 18 May 2002, V. Kummer (Volker Kummer fungarium VK-P-2529/3).

Notes: The sample identified here as Ar. cf. sporophleoides comes from Scheuer (1996), who considered this species a synonym of Ar. sporophleum, rejecting the criterion of Petrak (1959) and following the broad concept of Ellis (1965) instead. The sample analysed in the present work has fusoid conidia that resemble those of Ar. sporophleum, but the latter are wider, (5–) 6–8(–9) μm, vs. 5–5.5 μm in Ar. cf. sporophleoides. This subtle difference was the only useful diagnostic feature found between both clades, but additional samples are needed to confirm its utility.

Key to species of

1. Conidia navicular, fusiform or limoniform .........................................................................................................................................2

1. Conidia differently shaped ................................................................................................................................................................. 6

2. Conidia fusiform < 30 μm long ........................................................................................................................................................... 3

2. Conidia navicular > 30 μm long .......................................................................................................................................................... 5

3. Conidia < 15 μm long ......................................................................................................................................................................... 4

3. Conidia 15–25 μm long ............................................................................................................................................... Ar. ushuvaiense

4. Conidia < 6 μm wide .............................................................................................................................................. Ar. sporophleoides

4. Conidia 5–8.5 μm wide .............................................................................................................................................. Ar. sporophleum

5. Conidia > 15 μm wide .................................................................................................................................................... Ar. japonicum

5. Conidia < 15 μm wide ...................................................................................................................................................... Ar. caricicola

6. Conidia curved ................................................................................................................................................................................... 7

6. Conidia differently shaped ............................................................................................................................................................... 11

7. Conidia with rounded ends ................................................................................................................................................................ 8

7. Conidia with horned ends .................................................................................................................................................................. 9

8. Conidia < 15 μm long ...................................................................................................................................................... Ar. curvatum

8. Conidia > 20 μm long ............................................................................................................................................. Ar. kamtschaticum

9. Conidia with horns curved inwards .................................................................................................................................... Ar. luzulae

9. Conidia with horns curved outwards ............................................................................................................................................... 10

10. Conidia > 20 μm long ................................................................................................................................................... Ar. cuspidatum

10. Conidia < 20 μm long ......................................................................................................................................................... Ar. muelleri

11. Conidia globose to ovoid ................................................................................................................................................................. 12

11. Conidia angular ................................................................................................................................................................................ 14

12. Conidia ovoid or broadly ellipsoidal .................................................................................................................................. Ar. lobatum

12. Conidia globose ............................................................................................................................................................................... 13

13. Conidia 7.5–9.5 μm diam., with a colourless dome-shaped wall section ........................................................................ Ar. globosum

13. Conidia 6–8 μm diam .......................................................................................................................................... Ar. sphaerospermum

14. Conidia polygonal ....................................................................................................................................................... Ar. puccinioides

14. Conidia irregularly angular . ............................................................................................................................................................... 15

15. Conidia crenate in face view............................................................................................................................................ Ar. crenatum

15. Conidia not crenate in face view ...................................................................................................................................................... 16

16. Sterile cells with long lateral projections ............................................................................................................................. Ar. fuckelii

16. Sterile cells lacking lateral projections ............................................................................................................................................. 17

17. Conidia irregularly rectangular with concentric rings .................................................................................................... Ar. austriacum

17. Conidia oblong or irregular in face view ........................................................................................................................... Ar. morthieri

DISCUSSION

In the present study, genetic, morphological and ecological differences between Apiospora and Arthrinium are considered sufficient to support the taxonomic separation of the two genera. Smith were apparently the first to compare 28S nrDNA data from Apiospora sexual morphs and “Papularia”-like Arthrinium asexual morphs, and found them to form a monophyletic clade. Crous & Groenewald (2013) confirmed these results with a much-improved dataset including additional genetic markers and species, and considered both genera synonyms. Nigrospora was later shown to be the most closely related genus within Apiosporaceae by Wang , in agreement with previous morphological studies that highlighted the similarities between Nigrospora and its sexual morph Khuskia (Hudson 1963b) with the “Papularia”-like species of Arthrinium and Apiospora (Minter 1985, Eriksson & Hawksworth 1993). However, genetic differences between the “Papularia”-like species of Arthrinium that grow worldwide mainly on Poaceae, and some species found on Cyperaceae and Juncaceae in temperate or cold habitats (Ar. puccinioides, Ar. japonicum) could already be observed in the phylogenetic analyses conducted by Singh , Sharma , Wang , and Yan , although the issue was not discussed by these authors or investigated further. Pintos analysed the type species of Arthrinium, Ar. caricicola, and found that it groups with the samples occurring mainly on Cyperaceae and Juncaceae hosts in temperate or cold habitats, suggesting that this clade is not monophyletic with Apiospora and the “Papularia”-like species of Arthrinium.

The analysis of additional collections of Arthrinium associated with Cyperaceae and Juncaceae (and rarely Poaceae) found in temperate or cold habitats revealed that they are also related with Ar. caricicola within Arthrinium s. str. Phylogenetic inference suggests that this clade is not monophyletic with the one containing basauxic species occurring worldwide (also in tropical and subtropical habitats) mainly in Poaceae hosts, which are here combined to Apiospora. However, the host plants associated to Arthrinium and Apiospora seem to be diverse, especially for Apiospora, so they cannot be employed as a perfect diagnostic feature to discriminate both genera. For example, Ap. pterosperma has been found thus far, exclusively associated with Cyperaceae plants (genera Machaerina and Lepidosperma), and other species of Apiospora have been occasionally reported too in Carex or Juncus (e.g. Ar. phaeospermum sensu Ellis 1965, but these records need to be confirmed). On the other hand, samples of Ar. crenatum, Ar. curvatum and Ar. puccinioides have been found on Poaceae. Regarding the climate, all sequenced collections of Arthrinium s. str. come from temperate, cold or alpine climates. A few of them, such as Ar. cuspidatum, Ar. fuckelii or Ar. luzulae, occur in alpine habitats and snowbanks (Minter & Cannon 2018), and could be considered psychrophiles. Presently the only sequenced records of Arthrinium s. str. in Asia are those of Ar. japonicum, found in the northernmost part of Honshu island (Japan) in a cold climate, as well as a sequence obtained from soil samples (KT265189, Hu ) found at 4 800 m asl in the Tibet Plateau (China). Verified records of Arthrinium s. str. from tropical or subtropical habitats are lacking, suggesting that this genus could be absent from areas subjected to these climates.

On the contrary, Apiospora seems to be a cosmopolitan genus present in tropical, subtropical, temperate and cold climates. The type species, Ap. montagnei, was found on Poaceae hosts (Arundo, Piptatherum) not known for any species of Arthrinium or Nigrospora. The original samples were collected in Mediterranean lowlands (Perpignan, Algiers) where Arthrinium s. str. species have not been found. In the present work, a lectotype of S. apiospora (≡ Ap. montagnei) has been selected among the original collections stored at PC (Paris, France) as a first step to fix the identity of this species. A sample collected near Perpignan on Arundo sp. was chosen because of its good conservation status, and also because these are the first locality and plant host mentioned in the protologue. With this choice, Ap. marii and Ap. phragmitis are the most probable synonyms of Ap. montagnei, but additional samples obtained near the type locality are needed to confirm if other species of Apiospora occur on the putative host plant species (Arundo micrantha or A. donaciformis) and select an epitype with a known genetic profile.

The phylogenetic placement of other putative species of Arthrinium s. str. still needs to be resolved. Some of these are likely synonyms of earlier taxa on the basis of their morphological similarities (e.g., Ar. naviculare and Ar. carinatum = Ar. caricicola, Ar. bicorne and Ar. juncoideum = Ar. cuspidatum Cooke 1954). However, there could be other scenarios. For example, results obtained in the present study suggest that Ar. sporophleum and Ar. sporophleoides are distinct species with just slight morphological differences, while other names could also hide cryptic species (e.g. Ar. puccinioides). Therefore, putative synonymies with old names need to be reconfirmed with type studies, extensive sampling and genetic analyses. Information from other putatively distinct species of Arthrinium s. str. is also missing. Arthrinium kamtschaticum (first found in Carex sp. in Kamchatka, eastern Russia), has curved conidia resembling those of Ar. curvatum, but darker and larger (22–32 × 10–14 μm in Ar. kamtschaticum vs. 11–15 × 6–8 μm in Ar. curvatum) (Pollack & Benjamin 1969). Arthrinium cuspidatum, a species associated with Scirpus (Cyperaceae) and Juncus (Juncaceae) seems to occur in alpine areas of Europe (Suková et al. 2003) and the USA (Cooke 1954). It has lunulate conidia resembling those of Ar. luzulae, but in the first species the edges are pointing outwards, while in the latter they point inwards. Due to its habitat and morphological features, Ar. cuspidatum could be a genuine species of Arthrinium s. str. Arthrinium muelleri has curved conidia, 15–20 × 8–10 μm that sometimes point outwards, recalling those of Ar. cuspidatum (15–19 × 7–14 μm, Minter & Cannon 2018). It has been found in alpine areas of Switzerland (Ellis 1976) and Austria (Scheuer 1996), growing on Carex. Arthrinium fuckelii resembles Ar. morthieri because both species grow on Carex and have quadrangular conidia, but those of Ar. morthieri are smaller (11–16 × 11–16 × 5–9 μm vs. 7–9 × 16–19 × 3.5–5 μm in Ar. fuckelii, Gjærum 1967, Minter & Cannon 2018), and Ar. fuckelii has sterile cells lacking lateral projections (present in Ar. fuckelii). Arthrinium globosum has globose conidia similar to those of Ar. sphaerospermum, but they are larger (9 × 8 μm vs. 7 × 6 μm in Ar. sphaerospermum) and have a well-defined hyaline dome-shaped wall (Koskela 1983). Arthrinium s. str. might also include Ar. ushuvaiense, a taxon with lobate sterile cells and navicular conidia similar to those present in Ar. japonicum. It was found growing on Luzula (Juncaceae) in Tierra del Fuego (Argentina) (Speggazzini 1887, Gjærum 1967, Ellis 1971). Finally, Ar. lobatum was found in alpine areas of Venezuela. It has also lobate sterile cells but presents ovoid conidia. Despite the effect of altitude, this would be the first species of Arthrinium known to occur in a tropical region, so it needs to be confirmed.