Opegrapha diffracticola R.C.Harris & Ladd

Description

Type: - U.S.A. MISSOURI. MARIES CO.: Spring Creek Gap Conservation Area E of CR 340 (Old Hwy 63), ca. ½ mi N of US 63, 38°08'14"N, 91°48'08"W, 240–320m; floodplain forest, on Bacidia diffracta S. Ekman on bole of Juniperus virginiana, 4.xi.2002, Harris 46555 (NY, holotype; isotypes to be distributed as Lendemer, Lichens of Eastern North America Exsiccati V: 241).

Description: (From Harris & Ladd 2007) - Ascomata (Figs 1,2) lirelliform, growing on thallus and apothecia of Bacidia diffracta S. Ekman without visible damage to the host thallus but +/- deforming and darkening apothecia, sessile or slightly immersed, fusiform to } oblong, undivided to once branched, 0.2-0.5 x 0.1-0.2 mm, solitary and scattered or aggregated into irregular clusters to 3 x 2 mm; disk concealed by appressed lips. Exciple (Fig 3) brown-black, greenish black in K, entire, thickened below, upper part to 50-60 µm thick. Hypothecium thin, colorless. Epihymenium yellow-brown (K.). Hymenium colorless, I+ patchily bluegreen becoming orangish. Asci (Fig 4) clavate, with 8 +/- biseriately arranged spores. Ascospores (Fig 5) remaining colorless, 3.septate, with thin halo, 13.-15-(.16) x 4.5-5.5 µm. Pycnidia brown, +/- globose, 50-100 µm across. Conidia (Fig 6) rod-shaped, 4.5-5.5 x 1.0-1.2 µm.

Distribution and ecology: (From Harris & Ladd 2007) - Bacidia diffracta is widespread throughout the Ozarks in mesic woodlands, often associated with streams, and occasionally in drier woodland habitats. Substrates include lightly shaded boles of a variety of hardwoods, as well as commonly occurring on shaded boles of Juniperus virginiana. Opegrapha diffracticola probably occurs throughout the range of Bacidia diffracta, in the full range of habitats and substrates as the host. While most of the collections seen are from the Ozark region where Bacidia diffracta is common, Opegrapha diffracticola also occurs in Vermont and Wisconsin. While we have not borrowed the specimens of Bacidia diffracta cited by Ekman (1996), we assume such a search would locate additional records of the Opegrapha. As far as we know Opegrapha diffracticola is confined to B. diffracta and, interestingly, does not occur on the presumably closely related B. polychroa (Th. Fr.) Körber, even when the two taxa are adjacent on a single piece of bark [Harris 44745-C as B. polychroa (NY)].

Discussion: (From Harris & Ladd 2007) - Knowledge of many groups of lichenicolous fungi is largely inaccessible to non–specialists. We thought that there were no previous records of lichenicolous Opegrapha on Bacidia until Jana Kocourková in her review pointed out the existence of Opegrapha bacidiae R. Sant. nom. inval. (1952) on foliicolous Bacidia brasiliensis (Müll. Arg.) Zahlbr. It was included in a key without subsequent English or Latin description. Matzer (1996) could find no material. It differs from O. diffracticola in having 5–septate ascospores. When the ascomata are closely aggregated, Opegrapha diffracticola is somewhat similar to older, multilocular ascomata of the lichenicolous O. anomea Nyl. group. It differs in that the ascomata are lirelliform from the beginning and not subspherical.

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