Strigula guangxiensis S.H.Jiang, X.L.Wei & J.C.Wei

Jiang, Shu-Hua, Wei, Xin-Li & Wei, Jiang-Chun, 2017, Two new species of Strigula (lichenised Dothideomycetes, Ascomycota) from China, with a key to the Chinese foliicolous species, MycoKeys 19, pp. 31-42 : 35-37

Strigula guangxiensis S.H.Jiang, X.L.Wei & J.C.Wei sp. nov. Figure 3

Diagnosis.

Characterized by the thin thallus (30-45 μm thick), long asci (45-65 × 10-12.5 μm), aggregated pycnidia, large ascospores (15-25 × 2.5-5 μm), and 1-septate macroconidia (12.5-17.5 × 2.5-5 μm).

Type.

CHINA. Guangxi: Nanning, Long’an County, Longhu mountain natural reserve. 22°57'42"N, 107°37'40"E, 150 m alt., on living leaves, 1 Dec 2015, S.H.Jiang GX201511127 ( HMAS–L 0138040 - holotype).

Description.

Thallus subcuticular, dispersed into rounded to irregular, partly confluent patches, 1-2 mm across, a few to 3 mm, 30-45 μm thick, margins entire to crenulate, bright green to pale green, sometimes white in the centre, surface smooth. Photobiont Cephaleuros , cells 5-12 × 4-9 μm. Perithecia hemispherical, rarely found in specimens with aggregated pycnidia, small, scattered, round individuals with one or two perithecia occur in pure populations, basal part immersed in the thallus, 0.5-0.7 mm diam and 90-120 μm tall, black. Exciple prosoplectenchymatous, 7.5-12.5 μm thick, brown. Involucrellum carbonaceous, black, 20-90 μm thick. Interascal filaments unbranched, c. 1-2 μm thick. Asci obclavate, 45-65 × 10-12.5 μm. Ascospores 8 per ascus, biseriate, fusiform, 1-septate, distinctly constricted at the septum, distal cell slightly enlarged, 15-25 × 2.5-5 μm, 4-5 times as long as broad. Pycnidia producing abundant macroconidia, few on thalli producing perithecia and overgrowing them, single or most frequently aggregated in groups of 3-10, semi-immersed, wart-shaped, those producing macroconidia 0.07-0.15 mm diam, those producing microconidia 0.05-0.1 mm diam, black. Macroconidia bacillar, 1-septate, 12.5-17.5 × 2.5-5 μm. Microconidia fusiform, non-septate, 4-5 × 1.5-2 μm.

Chemistry.

No substances detected by TLC.

Habitat and distribution.

On the surface of living leaves in humid, semi-exposed forests of south China.

Etymology.

The epithet " guangxiensis " is the name of the province including the type locality of the new species.

Other specimens examined.

CHINA. Guangxi: Nanning, Long’an County, Longhu mountain natural reserve. 22°57'42"N, 107°37'40"E, 150 m alt., on living leaves, 1 Dec 2015, S.H.Jiang GX201511078 ( HMAS–L 0138044), GX201511087 ( HMAS–L 0138041), GX201511071 ( HMAS–L 0138065), GX201511107 ( HMAS–L 0138043), GX201511130 ( HMAS–L 0138042).

Remarks.

Strigula guangxiensis is most similar to Strigula subelegans , having essentially the same ascospore dimensions, but differs in the smaller and thinner thallus (5-15 mm across and 30-70 μm thick in Strigula subelegans ; Lücking 2008). In addition, the perithecia and pycnidia are usually separated on different thallus patches and the pycnidia are often aggregated (dispersed in Strigula subelegans ) ( Lücking 2008). Strigula wandae M. Cáceres & Lücking is also similar in appearance, but distinguished by the oblong-ellipsoid ascospores, with cells of equal size, solitary pycnidia, and smaller macroconidia (12-15 × 2.5-3 μm) ( Lücking et al. 2003, Lücking 2008).

With respect to aggregated pycnidia, four other species of Strigula have aggregated pycnidia developing as in similarly with Strigula guangxiensis : Strigula schizospora , which can be distinguished by the smaller ascospores (8-12 × 2-2.5 μm), usually breaking into parts while still within the asci, and the smaller macroconidia (4-6 × 1.5-2 μm) ( Santesson 1952); Strigula lacericola P.M. McCarthy, has smaller, narrow ascospores (10-14 × 1.5-2.5 μm), with cells of equal size and smaller, and non-septate macroconidia (6-8 × 1-2 μm) ( McCarthy 2009); Strigula novae-zelandiae (Nag Raj) Sérus., characterised by the circular thalli with a crenulate to deeply digitate margin and especially the pycnidia producing polarilocular macroconidia ( Sérusiaux 1998); and Strigula antillarum , which has a thinner thallus (20-30 μm thick) and longer asci (60-70 × 8-11 μm) ( Lücking 2008). According to our phylogenetic analyses, even though the differences in morphology are subtle, the species are readily separated in the molecular phylograms (Figure 1).