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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) does 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 are very few records of this species from North America and all records on MycoPortal are recent, except for one dubious specimen from SE USA. Is it a recent introduction to America or is it that rare? Widespread and common in Europe, also Russia and the Caucasus. Mushroom Observer records are from Austria and Portugal. MycoPortal records from USA, South America, Europe, Pakistan, India, South Africa, Philippines, New Zealand. Included in a list for Australia.
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 but Stereum spadiceum is the one described as bleeding red if bruised, not Stereum gausapatum. So it seems the concepts were confused. The one herbarium collection that may be correct is from Texas, 1918, identified by C.G. Lloyd as Stereum spadiceum. These 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 lends another clue that Porostereum spadiceum does not actually occur in the USA.

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. Binder et al. (2013) showed Porostereum spadiceum is closely related to Bjerkandera adusta so it may end up in the Bjerkanderaceae if that family is recognized.
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:
Lentz (1955) Stereum and Allied Genera of Fungi in the Upper Mississippi Valley ; Ellis, Bartholomew, and the Fungi Columbiani exsiccati ; Binder et al. 2013. Phylogenetic and phylogenomic overview of the Polyporales, Mycologia 105(6): 1350-1373.
Records online:
Mushroom Observer (Austria, Portugal) ; MycoPortal
Taxon links:
327227 MycoBank ; Index Fungorum ; Species Fungorum