Cortinarius koldingensis Frøslev & T.S. Jeppesen, 2015

Frøslev, Tobias Guldberg, Jeppesen, Thomas Stjernegaard & Dima, Bálint, 2015, Cortinarius koldingensis - a new species of Cortinarius, subgenus Phlegmacium related to Cortinarius sulfurinus, Mycol Progress 14 (73), pp. 1-7 : 4-7

Cortinarius koldingensis Frøslev & T.S. Jeppesen , sp. nov.

MycoBank MB812989

Figs. 2 – 7.

Diagnosis: A medium-sized Phlegmacium, distinguished by pale greenish yellow colours, a distinctly fibrillose pileus, weak alkaline colour reactions on all tissues except the rhizomorphs, which become pink/red. Spores amygdaliform to citriform, coarsely verrucose, 11 – 13.5×6.5 – 7.5 μm.

Etymology: The epithet refers to the only locality from where the species is presently known, Kolding.

Holotype: Denmark, Østjylland : Kolding , Marielund, on east shore of lake, south of Naturskolen , under Fagus sylvatica in loose mineral-rich soil (GPS: 55.499502 9.489281, 6.X.2013, T.G. Frøslev (Danish Basidiomycote Atlas no#: TF2013-640926 ) ( C-F-100309 ). GenBank accession number (ITS region): KT222911 .

Detailed description

Macrocharacters — PILEUS up to 10 cm across, convex, but soon expanded, often irregularly wavy with depressed centre; initially glabrous with only inconspicuous fibrils at margin, but soon becoming conspicuously radially fibrillose near the margin, centre sometimes with small (1 – 2 mm) brown flakes of universal veil; initially homogeneously pale yellow with a greenish tinge (1-2A2-4), soon mixed with brownish colours, and then overall with a pale green-brown tinge (±4(A-)B4), at the most exposed/oxidized parts predominantly green-brown (5CD6), at margin paler cream-yellow, at centre darker yellowish brown (±5F6); when expanded/mature with conspicuous brownish radial fibrils towards margin; where damaged only slightly brownish; pellicle easily peelable. LAMELLAE emarginate, medium spaced, yellow (2B4) with a greenish tinge when young, then greenish grey-yellow (3A5 to 3B4). STIPE relatively short, up to 60× 15 mm (in upper part), often shorter than pileus diameter, often gradually widening towards bulb in the lower fourth, with a sharply marginate bulb, pale greenish yellow (1A2), palest at apex, bulb margin with sparse, ± brownish veil remnants, bulbipellis and rhizomorphs whitish, mycelium ± yellow. CONTEXT cream to pale greenish yellow (1A3), strongest coloured in hygrophanous streaks in stipe. SMELL faint but pleasant like parsley (similar to C. sulfurinus ). MACROCHEMICAL REACTIONS (10 % KOH): brownish, not reddish but yellowish brown (5E6), in context paler brownish (4B5), on bulb margin same tone as pileus, but darker, almost blackish, on bulbipellis seemingly negative, on rhizomorphs strongly blood red to pink-red.

Microcharacters — BASIDIOSPORES amygdaliform to citriform, coarsely verrucose. 95 % conf.: 11 – 13.5× 6.5 – 7.5 μm; av. 12.28×7.05 μm; Q =1.6 – 1.88; Qav.=1.74 (n = 54). BASIDIA 35 – 55× 8 – 11 μm, clavate, 4-spored, with clamps; subhymenium hyphae 4 – 6 μm wide, trama hyphae up to 12 μm wide, with sparse pigmentation, lamella edge fertile, without differentiated cheilocystidia, but with basidiole-like, sterile hyphae. PILEIPELLIS simplex (observed fresh and dried in 2 % NH 4 OH), cutis thick (approx. 250 μm), at surface hyphae 3 – 5 μm wide, gelatinous, entangled, below slightly wider and more parallel, (when scalp cuts are viewed from above, single contrasting entirely golden brown hyphae can be seen in the layer below the glutinous layer, most likely corresponding to the hyphae macroscopically seen as dark fibril near the margin); below with a layer (approx. 250 μm) of more or less parallel hyphae forming an agglutinated brownish layer; trama hyphae hyaline, approx 80×15 μm; patches of veil on the pileus composed of more brownish, narrower (1.5 – 4 μm wide) entangled hyphae. All hyphae types with clamps.

Habitat & distribution — So far known only from Marielund, Kolding, Denmark — a nemoral, suburban forest/ park dominated by Fagus sylvatica . At the locality it has been recorded from two sites approx. 700 m apart — most likely representing at least two individuals. At the northernmost locality, which is presently almost a closed forest, the species grows on the slope of a small hill further influenced by erosion from hiking trails. At the other site (the type locality), which is more open and exposed in a park-like area, it grows on a small slope between a road and the shore of a small lake only 2 m from the water. The site is thus influenced by erosion by the road, the sloping terrain and from general exposure. In both sites the soil is almost without a humus layer, and the species grows more or less directly in the mineral soil influenced by erosion. In both sites it grows among other ectomycorrhizal macromycetes ( Cortinarius spp., Boletus spp., Ramaria spp.) that are uncommon to very rare on a national scale.

Discussion — Phylogenetically C. koldingensis is wellsupported (BS= 100 %) and belongs to a small subclade (Sulfurini) within the large Fulvi/Calochroi clade with high support (BS=99 %). The clade hosts species with relatively little anthraquinonoid pigments, which traditionally are treat- ed in the section Fulvi. The lineage contains two European species, C. sulfurinus and C. koldingensis . They differ from each other by 16 nucleotide and 5 indel positions within the ITS region. They are both distinguished from similar species with yellow pileus and lamellae by the distinct blood-red alkaline reaction on the mycelial cords in combination with nonred alkaline reactions elsewhere. Furthermore, they are characterized by pale greenish yellow colours, an often weak, ̎ parsley̏- like odour and large spores. Cortinarius koldingensis has a pileus which is most often uneven and wavy with a somewhat depressed centre, and a conspicuously fibrillose margin; furthermore, the stipe is most often relatively short. Cortinarius sulfurinus , in contrast, has a pileus which is mostly hemispherical and later homogeneously expanded

with an only slightly fibrillose margin, and the stipe is generally at least as long at the pileus diameter. Cortinarius koldingensis is currently known only from a single locality in a nemoral, thermophilous deciduous forest, where it grows with several classic deciduous forest-associated Phlegmacia (e.g., C. caerulescens (Schaeff.) Fr., C . vulpinus (Velen.) Rob. Henry, C. luhmannii Münzmay, Saar & B. Oertel, C. calochrous (Pers.) Gray, C. olidus J.E. Lange ). Cortinarius sulfurinus occurs mainly in hemiboreal, boreal and subalpine habitats with conifers on richer soils, often in the company of other conifer associated Phlegmacia, but is also found in boreonemoral and nemoral habitats with Fagus and Tilia . Cortinarius sulfurinus var. fageticola was thus described from Scania, Sweden ( Brandrud et al. 1998), as a broad-leaved forest variety of the presumed strict coniferassociated species C. sulfurinus . It has been shown ( Frøslev et al. 2007) that the type collection of C. sulfurinus var. fageticola has an identical ITS sequence with typical specimens of C. sulfurinus s. str. from coniferous forests. Furthermore, studies have shown that the presumed differences in morphological characters between the two varieties is of little value (i.e., overlapping), and they are now considered synonymous (T.E. Brandrud, pers. comm.).

Cortinarius humolens and C. osloensis Brandrud, T.S. Jeppesen & Frøslev may occur in the same habitats as C. koldingensis , but are recognized by smaller spores (<11 μm), the lack of blood-red alkaline reaction on rhizomorphs, and the earth-like to radish-like smell. Cortinarius natalis D. Antonini & M. Antonini — so far only known from southern Europe — is generally smaller, lacks the alkaline reaction, has a smooth pileus, and smaller spores. Cortinarius lavandulochlorus Eyssart. is also somewhat similar, but it has no alkaline reaction on the mycelium, and is further distinguished by violaceous lamellae in its typical form. Cortinarius sulfurinus s. Lange (1938) represents another taxon — C. langeorum Frøslev & T.S. Jeppesen — as discussed in Frøslev et al. (2006b), and this species is also superficially similar to C. koldingensis , but differs by lack of alkaline reaction on mycelium and lack of yellow colours on lamellae and in context.

The Sulfurini lineage also contains two North American species: C. oliveopetasatus M.M. Moser and the recently described Cortinarius subsulfurinus Ammirati et al. ( Dima 2015) , which was identified as C. guttatus Rob. Henry by Moser and Ammirati (1996). However, C. guttatus is described from France and now has a completely different interpretation (as belonging to the Percomes/Cliduchi lineage). Cortinarius koldingensis is genetically well-delimited from these two species, with 16 nucleotide and 6 – 7 indel positions. From the large European material genetically screened we have not encountered matches to any of these, and we assume that they are strictly NA species. According to the original description of C. oliveopetasatus ( Moser and Ammirati 2000) , this species has much darker olive-green pileus, but shows similarities in spore size and seemingly also has a tendency towards innate fibrils near the margin. The first description of C. subsulfurinus (as ̎ C. guttatus̏ in Moser and Ammirati 1996) describes it as a species with affinities to C. percomis due to a peculiar spicy smell — a marjoram-like smell different from the more parsley-like smell of C. koldingensis . Otherwise, the colours and morphology seem to be very close to C. koldingensis , which is confirmed by the description in Dima (2015). Both NA taxa have been recorded from mixed coniferous forests. It will be interesting to see whether these two NA species share the typical pink alkaline reaction of the rhizomorphs seen in C. koldingensis and C. sulfurinus .

Cortinarius koldingensis is so far known only from one locality, and intense sampling in similar habitats has failed to provide evidence of other established populations. The species has likewise not been recorded in the intense ITS sequencing of type material and illustrated material from other studies (e.g., Frøslev et al. 2007; Liimatainen et al. 2014). Thus, we postulate that the species is rare in Europe, but a more solid knowledge of the species distribution and frequency of occurrence await further studies.

Figures

Figs. 2–7 Cortinarius koldingensis. 2. Holotype of Cortinarius koldingensis— TF2013-640926 (C-F-100309), photo by TGF. 3. Map of the locality, Marielund in Kolding, Denmark, where the species has been found; site 1, northern (55.505710, 9.487110), site 2, southern/holotype (55.499502 9.489281), contains data from the Danish Geodata Agency, Topo 25, June 2015. 4) Red/pink alkaline reaction (10 % KOH) of the rhizomorphs (holotype), photo by TSJ. 5) Close-up of radially fibrillose structure of pileus with single darker cuticular fibrils (TF2013-640909), photo by TGF. 6) Basidiospores (holotype), scale bar 10 μm, photo by TGF. 7) Close-up of small (up to 2 mm) brownish velar scales on pileus (holotype), photo by TSJ