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Porostereum spadiceum (Pers. : Fr.) Hjortstam & Ryvarden

Synopsis Fungorum 4: 51 (1990)

Excluded:
Not known for the Chicago Region. The name Stereum spadiceum was misapplied to Stereum gausapatum by past authors. Ryvarden (2010) and Liu et al. (2018) do not include this species as being present in the Americas.
Uncommon name:
Rußbrauner Schichtpilz.
Fruitbody:
Annual stereoid crust fungus, effused (resupinate) to effused-reflexed. Upper side brown, felt-like tomentose, sulcate. Online photos show green coloration (algae) on older portions. Margin pale or white. Underside brown, smooth or wrinkled. In dried specimens the underside is typically cracked. Microscopic features: generative hyphae with clamps, skeletal hyphae brown, pseudocystidia encrusted.
Similar species:
These are more reliably separated on microscopic characters. Lopharia cinerascens has large projecting pointed and encrusted cystidia (use hand lens). Punctularia strigosozonata, under the microscope, has dendrohyphidia (dendrophyses, branched cells) instead of encrusted pseudocystidia. Hymenochaete rubiginosa has reflexed caps that hang down and the upper surface becomes smooth and nearly black. Hymenochaetopsis tabacina has tiny spines on lower surface (use hand lens). The darker colors and white margin might help separate it from some Stereum species, but it can be confused with S. gausapatum. There are other similar stereoid crusts on conifers.
Ecology:
Saprobe on oak and other dead hardwoods; on branches or logs.
Phenology:
Persistent fruitbodies might be found year-round.
Biogeography:
There is only one Porostereum spadiceum record from North America on MyCoPortal. The others are Stereum spadiceum, which are likely all missapplied names (see below). I wondered if it was a recent introduction to America or if it was rare? But it is treated in the literature as absent from the Americas (Ryvarden 2010, Liu et al. 2018). There are MyCoPortal records from Europe, South Africa, Middle East, Asia, Australasia. Liu et al. (2018) say that Porostereum spadiceum is known from Europe, Armenia and Morocco.
Chicago Region status:

Excluded. What I thought was a species with no recent records turned out to be one with no correct historic records.

This species was described in Moffatt (1909) but I had never identified it. In August 2014, I started assembling this page as an example of a species that had no recent records. When researching taxonomy and records online I thought that photos of it resembled an unknown stereum-like fungus I had found recently but the microscopic characters were quite different; it turned out to be Punctularia strigosozonata.

A few days later I looked through the Field Museum herbarium (F) collections and discovered that Harper's Chicago specimens and most of the U.S.A. collections of early collectors from 1887 to 1914 (including Fungi Columbiani exsiccati) are misidentified and many seem to be Stereum gausapatum; most are labeled as being on oak. The Harper collection from Glencoe IL has both names on the original label with an equal sign suggesting they are synonyms. But Harper and others also have different specimens labeled correctly as Stereum gausapatum.

Both species are described in Moffatt (1909) but Stereum spadiceum is the one described as bleeding red if bruised, not Stereum gausapatum. So it seems the concepts were confused. Many BPI herbarium collections (on MyCoPortal) were identified by C.G. Lloyd as Stereum spadiceum. Herbarium specimens require microscopic examination to sort out their identities.

Next, I searched online regarding the exsiccati of Stereum spadiceum, and this led me to the work of Lentz (1955), a copy of which I had luckily obtained two weeks prior. Lentz examined the Fungi Columbiani exsiccati (see page 53) and found that numbers 2589, 2883, 4292, 4987, 5092 are all Stereum gausapatum; the same set of five I examined earlier in the day at the Field Museum. So this problem had already been sorted out but the findings of Lentz had not been applied to our collections. Lentz worked with specimens from many herbaria of America and Europe but unfortunately not those of the Field Museum.

Ryvarden (2010) describes 4 Porostereum species from Cuba, Mexico, and South America. He equates the type P. phellodendri Pilát with Thelephora spadicea Pers.:Fr. but does not treat it in his book and does not indicate any species existing in USA or Canada. This gave another clue that Porostereum spadiceum may not actually occur in the USA.

Update May 2018: Liu et al. (2018) say that Porostereum spadiceum is known from Europe, Armenia and Morocco. It seems most likely that the many USA and Canada specimens labeled Stereum spadiceum from 1848–1942 are all missapplied identications. The few collections on MyCoPortal from 1999–2014 (all as Stereum spadiceum) are most likely data errors and represent 1899–1914 (this is a frequent problem on MyCoPortal). There is only one modern Porostereum spadiceum collection; it is from 2008 in West Virginia and this identification should be verified. There are no observations of current Porostereum species on Mushroom Observer (as of May 2018), other than some from Austria and Portugal, which are listed as the synonym Lopharia spadicea.

Type:
Apparently from Meissen (Latin: Misnia), Germany.
Taxonomy:
I am using Porostereum which follows Fungi Europaei - Corticiaceae s.l. (2010). Index Fungorum lists the current name as Porostereum (in Phanerochaetaceae) while MycoBank uses Lopharia (in Polyporaceae), but MycoBank does put Porostereum in Phanerochaetaceae. This species has another homotypic synonym in Lloydella (1901). It was redescribed eight times by other authors and these heterotypic synonyms are in Stereum and Thelephora plus Corticium and Peniophora. Species Fungorum shows the tangle of synonyms.
Mycobank (July 2018) indicates that Porostereum spadiceum was not sanctioned by Fries but rather that a different taxon Stereum spadiceum Fr., Epicrisis Systematis Mycologici: 549 (1838) is sanctioned as Thelephora spadicea Fr., Elenchus Fungorum 1: 176 (1828) and this is a synonym of Thelephora gausapata Fr., Elenchus Fungorum 1: 171 (1828) [= Stereum gausapatum]. Perhaps this was part of the confusion between Stereum gausapatum and Porostereum spadiceum.
Specimens examined:
Fungi Columbiani exsiccati 2589, 2883, 4292, 4987, 5092 (see above); and other herbarium collections with the misapplied name.
Description links:
See photos and drawings on MycoBank ; Micro photos at asturnatura.com ; Photos from Poland and Germany.
Related links:
About Ellis, Bartholomew, and the Fungi Columbiani exsiccati: The New York Botanical Garden
Bernicchia, A., S. P. Gorjón. 2010. Corticiaceae s.l. Series: Fungi Europaei Volume: 12 [English]. 1008 pp. Publisher: Editrice Giovanna Biella.
Binder, M., A. Justo, R. Riley, A. Salamov, F. Lopez-Giraldez, E. Sjökvist, A. Copeland, B. Foster, H. Sun, E. Larsson, K-H. Larsson, J. Townsend, I. V. Grigoriev, and D. S. Hibbett. 2013. Phylogenetic and phylogenomic overview of the Polyporales. Mycologia 105(6): 1350-1373.
Lentz, P. L. 1955 [1956]. Stereum and Allied Genera of Fungi in the Upper Mississippi Valley. Series: Agriculture monograph; no. 24. Washington, D.C.: U.S. Dept. of Agriculture. 98 pp. Biodiversity Heritage Library.
Liu, S.-L., K. K. Nakasone, S.-H. Wu, S.-H. He, Y.-C. Dai. 2018. Taxonomy and phylogeny of Lopharia s.s., Dendrodontia, Dentocorticium and Fuscocerrena (Basidiomycota, Polyporales). Mycokeys. 32: 25-48.
Moffatt, W. S. 1909. The Higher Fungi of the Chicago Region: Part I, The Hymenomycetes. Natural History Survey, Bulletin No. VII, Part I. Chicago Academy of Sciences. 156 pp., 24 plates.
Ryvarden, Leif. 2010. Stereoid fungi of America. Synopsis Fungorum 28.
Records online:
Mushroom Observer (Austria, Portugal) ; MycoPortal
Taxon links:
327227 MycoBank ; Index Fungorum ; Species Fungorum