Hypoxylon liviae

              

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TROM39300

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Hypoxylon liviae Granmo.

Stroma effused-pulvinate on bark, irregularly elongate, with inconspicuous perithecial mounds and abrupt margin, 50 mm long x 7-28 mm broad x 0.6-1mm thick; surface brown vinaceous (84) to vinaceous buff (86) or greyish sepia (106) due to a persistent greyish pruina; orange brown granules beneath surface with KOH-extractable pigments luteous (12) to sienna (8); the tissue between the perithecia greyish sepia (106) to blackish at the base.

Perithecia obovoid, 200-250 Ám diam x 250-400 Ám high.

Ostioles umbilicate, appearing as black dots on stromatal surface.

Asci 150-170 Ám total length, the spore-bearing parts 65-80 Ám long x 7.5-9 Ám broad, the stipes 80-90 Ám long, with apical ring discoid, amyloid, 1 Ám high x 2.5 Ám broad.

Ascospores dark brown, ellipsoid nearly equilateral, 9.5-11.5 x 4.5-5.5 Ám, with a straight, very conspicuous germ slit spore-length, uniseriate in the ascus; perispore dehiscent in 10 % KOH. Anomalous ascospores in 4-spored asci are fairly abundant and reach 15 Ám long x 7.5 Ám broad, and a relatively high number of asci are 1-spored and contain a single giant ascospore 40-56 Ám long x 5.5-7.5 Ám broad, cylindrical with narrowly to broadly rounded ends, with a spore-length germ slit.

Anamorph not seen, referable to Virgariella according to Granmo (2001).

Habitat: apparently specific for Sorbus aucuparia, growing on inner side of bark of dead branches that are not in contact with the soil, more rarely on wood (Granmo, 2001).

Known distribution: so far known from northern Norway (Granmo, 2001).

Specimen examined: NORWAY, Nordland: Evenes Forra, Hoggvik, 0.6 km NO Forrhaugen, 06 Aug. 2001, TROM 39600, on Sorbus aucuparia, leg. & det. A. Granmo.

Notes: The above description is based on a specimen kindly sent to FC by Dr. Granmo, and therefore is less complete than the original description, to which we refer the reader for more details (Granmo, 2001). Nevertheless, we observed in this specimen that some asci contain a single giant ascospore occupying most of the spore-bearing part usually containing eight ascospores. These giant ascospores are not much broader than normal ones but are 4-6 times longer, and have a spore-length germ slit. Anomalous macro-ascospores produced in few-spored asci are not rarely encountered in xylariaceous fungi, but the occurrence of these particularly large ascospores seems worth being reported. According to Dr. Granmo (pers. comm.), this feature is probably exceptional.

Hypoxylon liviae is a distinctive taxon, easily separated from related species through the combination of sepia effused-pulvinate stromata, small perithecia with umbilicate and black ostioles, a well-developped brown tissue between and beneath perithecia with luteous to sienna KOH-extractable pigments and dark brown ascospores which are nearly equilateral. Its host-specificity for Sorbus aucuparia and its northern distribution are likewise reliable characters. In other parts of Europe, it should be searched for in mountain regions, in locations favorable to Sorbus aucuparia.

Its secondary metabolites profile is still unknown.