Hypoxylon commutatum Nitschke

TELEOMORPH | CULTURES AND ANAMORPH | SPECIMENS EXAMINED | NOTES

NOTES

Material of L. Fuckel's Fungi Rhenani Exsiccati no. 1056 was originally determined by him as H. coccineum Bull. [= H. fragiforme]. On the specimen label, Fuckel indicated that this exsiccatum was gathered from both Fagus and Carpinus, and included two morphs of H. fragiforme: "a. Fungus spermogoniferus" and "b. Fungus ascophorus". Nitschke (1867) considered that this exsiccatum is composed of two fungi-H. commutatum and H. coccineum. He cited no. 1056-a and no. 1056-b, presumably from Fagus under H. coccineum, and also considered them to be the "spermogoniferus" morph and the "ascophorus" morph of this fungus, respectively. For the part of no. 1056 presumably from Carpinus, Nitschke (1867) named it a new species, H. commutatum. Miller (1961) reported that no. 1056-a at the Nitschke herbarium of B is sterile, and listed no. 1056-b at K as H. fragiforme. Miller's observations may have reflected what Nitschke (1867) observed on the part of exsiccatum no. 1056 collected presumably from Fagus. From the Nitschke herbarium, we have examined a specimen which has Fuckel's exsiccata number 1056 and appears to be a part or the part of original material that was described as H. commutatum by Nitschke, presumably from Carpinus; this specimen is selected as the lectotype. This fungus is peculiar in having a highly reduced or no ascal apical ring, by which it can easily be separated from H. fragiforme. Moreover, it differs from H. fragiforme in having smaller ascospores and in not having both white and red granules in the stromata. Fungi Rhenani Exsiccati no. 2197 [= Herb. Barbey-Boissier no. 297] was identified as H. commutatum by Fuckel. The part of this exsiccatum at WSP is H. fragiforme, whereas the part among Shear's microscope slide collections is H. howeianum. Miller (1961) also reported that those parts of exsiccata no. 2197 at K and at the National Fungal Collections of BPI are H. howeianum, and the part at NY is H. fragiforme.

Petrini and Müller (1986) synonymized H. commutatum with H. rubiginosum var. perforatum (Schwein.: Fr.) L. E. Petrini [= H. perforatum (Schwein.: Fr.) Fr.] from which the former differs mainly in having orange stromatal pigments and in having a highly reduced or no ascal apical ring. Several other Hypoxylon are also known to have highly reduced ascal apical rings, including H. cercidicolum, H. intermedium, H. notatum, H. shearii, and South American collections of H. diatrypeoides. Hypoxylon commutatum differs from H. cercidicolum in not having the stellate ruptured host tissue surrounding the stromata; from H. intermedium and H. shearii in having a different stromatal surface color, in having different stromatal pigments in KOH, and in having smaller ascospores; from H. notatum in having different stromatal pigments and in having smaller ascospores; and from South American collections of H. diatrypeoides in having much smaller ascospores.

Hypoxylon commutatum is known only from the type material. It seems possible that it is host-specific on Carpinus in Europe and possibly has been confused with H. fragiforme, superficially similar forms commonly encountered on Fagus. Hypoxylon pelliculosum is similar but differs in having a distinct ascal apical ring and in having conspicuous coil-like ornamentation on the ascospore perispore.