Search on : Taxa descriptions


Page number:436 
Remarks (internal):Tricholoma olivaceotinctum has long been known under the name T. squarrulosum in Fennoscandia (e.g. Ryman & HolmÃ¥sen 1984, Gulden 1992, Salo et al. 2005). This is understandable since both the present species and the true T. squarrulosum share important macroscopical characters, i.e. the blackish squamulose pileus in combination with a pale greyish to dark brownish grey stipe. After field studies in different parts of Europe, we realised that the species occurring in boreal coniferous forests in Scandinavia clearly differs morphologically from the species occurring mainly in broadleaved forests from southern Scandinavia to the Mediterranean zone. The separation is well supported by ITS sequence patterns (results not shown). Tricholoma squarrulosum was originally described by Bresadola (1892) from Trento in Italy, and in southern Europe the name is consistently used for a rather common Tricholoma species with blackish scales on the cap and stem, large spores and an occurrence mainly in thermophilous Quercus forests (e.g. Bon 1984, 1991, Riva 1988). We see no reasons to doubt this interpretation of the original concept of Bresadola. We have studied the type of T. squarrulosum, which is in fairly good condition. It is macroscopically similar to our own dried specimens of this species and the spores are long (6.5-8.5 x 3.5-4.5 µm), in agreement with our own material.
Tricholoma squarrulosum occurs also in thermophilous deciduous forests in central and northwest Europe, north to Denmark, south Sweden and England, where it is often referred to as T. atrosquamosum (e.g. Noordeloos & Christensen 1999). We consider this interpretation of T. atrosquamosum to be inconsistent with the original intention of the epithet. According to the protologue of Chevalier (1837), Agaricus atrosquamosus occurs in mossy mountainous forests ("inter muscos in sylvis montosis Hercyniae") and the iconotype (no type specimen has been found) depicts a Tricholoma species with a pale, smooth stipe. We find this to be consistent with the interpretation of T. atrosquamosum by several authors in central and northern Europe (e.g. Gulden 1969, Dähncke & Dähncke 1979), and consider T. atrosquamosum to be a sister taxon to T. orirubens, with weaker colour reactions and a restriction to coniferous forests (Christensen & Heilmann-Clausen 2008). Preferably a neotype should be collected in southern Germany to stabilize the interpretation of this name.
We have found no indication that Elias Fries was familiar with T. olivaceotinctum. This probably reflects that the species was lacking or very rare in his collecting grounds around Femsjö and later Uppsala. Even in other classical mycological works from the Nordic countries we have not come across any other taxa matching with the species. Therefore we find it necessary to describe the species as new.
Macroscopically, T. olivaceotinctum resembles T. squarrulosum, but it is distinguished by differences in ecology and distribution, and by having more slender basidiocarps with distinct olivaceous tinges, especially at the cap margin. Microscopically it is distinguished by having comparably small spores. The species may even be confused with T. atrosquamosum, which may occur in quite similar habitats. From this species T. olivaceotinctum is best separated based on the distinctly greyish or brown stipe and olivaceous colours at the cap margin. Furthermore, T. atrosquamosum is mainly a southern boreal species in Fennoscandia and the zone where these two taxa co-occur is limited.
Description type:Original description 
Description:Tricholoma olivaceotinctum Heilm.-Claus. & Mort. Christ., sp. nov.
MycoBank MB 512781 GenBank FJ544861
Pileus 38-75(-120) mm, at first convex, hemispherical or obtusely conical, expanding to broadly applanate or even planoconcave, typically retaining a small umbo, densely covered by small, very distinct, dark olivaceous brown to black, recurved scales on a cream to olivaceous grey background, olivaceous colours normally distinct, especially in young specimens, which may be almost sulphur yellow at the edge. The scales are often forming a confluent dark spot in the centre. Lamellae emarginate, rather narrow to normal, normal to rather dense, almost white to pale greyish, often with a faint olivaceous tinge, sometimes with small black spots. Stipe 30-80(-150) x 6-20(-30) mm, cylindrical, mostly distinctly swollen at base, white to pale brownish grey or pale olivaceous grey, smooth or slightly greyish fibrous to scaly at apex. Context soft, brittle to rather elastic, often hollow in stem, whitish to pale olivaceous grey, sometimes becoming darker upon exposure. Smell weak, but distinctly spicy, sweetish, reminding of honey often intermixed with pepperish components, after cutting faintly to strongly farinaceous. Taste mild to slightly bitter, distinctly farinaceous.
Spores hyaline [170, 8], 4.0-6.7 x 2.8-4.9 µm, average 5.0-5.7 x 3.5-4.1 µm, subglobose to oblong, Q = 1.1-1.8, average = 1.36-1.54. Basidia 18-27 x 5-7 µm, 4-spored. Pileipellis a cutis of ± parallel hyphae breaking up in curved, trichoderm scales, hyphae (13-)17-50(-75) x 7.5-15(-22) µm, partly incrusted with brownish or blackish pigment. Clamp connections absent.
Distribution and Ecology - Tricholoma olivaceotinctum is confined to moist Picea stands mostly on somewhat calcareous soils. It is widely distributed in Fennoscandia, but is generally rare, with most records from the lime-rich soils in the provinces of Medelpad and Jämtland in central Sweden. According to Salo et al. (2005, sub nom. T. squarrulosum) it is more or less restricted to old-grown stands in Finland, which agrees with our personal experience from Norway and Sweden. It seems to be a truly boreal taxon, restricted to the natural Picea forest zone in central and northern Fennoscandia. The species is red-listed in Finland, Norway, and Sweden (Gärdenfors 2005; Salo et al. 2005; KÀ¥lÀ¥s et al. 2006; sub nom. T. squarrulosum). We know of no collections south of central Sweden and southern Norway and consider it unlikely that it should occur together with the true T. squarrulosum in any kind of habitats in Europe.
Taxon name: