Strigula acuticonidiarum 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 : 34

Strigula acuticonidiarum S.H.Jiang, X.L.Wei & J.C.Wei sp. nov. Figure 2 a–d

Diagnosis.

Differs from Strigula antillarum in the almost entirely immersed perithecia, and longer macroconidia with more acute ends.

Type.

CHINA. Guangxi: Nanning City, 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 GX201511085 ( HMAS–L 0138045 - holotype).

Description.

Thallus subcuticular, continuous or dispersed into rounded to partly confluent patches, 0.5-4 mm across and 10-25 μm thick, margin entire to crenulate, distinct lobes absent, bright to dark green. Photobiont Cephaleuros , cells angular-rounded, 5-15 × 4-10 μm. Perithecia immersed to erumpent, covered by thalline tissue, mostly up to the ostiole, hemispherical, 0.3-0.5 mm diam and 100-140 μm tall, dark green, but the uppermost part often black. Exciple prosoplectenchymatous, 10-25 μm thick, colourless to brown. Involucrellum carbonaceous, 22.5-55 μm thick, black. Interascal filaments unbranched, c. 1-2 μm thick. Asci obclavate, 50-65 × 8-12 μm. Ascospores 8 per ascus, biseriate, fusiform, 1-septate, distinctly constricted at the septum, 12.5-20 × 3.7-5 μm, 2.5-5.5 times as long as broad. Pycnidia producing macroconidia numerous, black, wart-shaped, 0.1-0.15 mm diam. Macroconidia 1-septate, often constricted at the septum, ends acute, usually with 1-2 oil droplets per cell when fresh, 15-22.5 × 3-4 μm, 4-7.5 times as long as broad. Microconidia not seen.

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 " acuticonidiarum " is a compound of a Latin adjective “acutatus” (a, um, and acuti- in Latin comp.) meaning sharply pointed, and “macroconidiarum”, a plural genitive of the Latin neuter noun, “macroconidium”. This recalls the acute ends of the macroconidia.

Other specimens examined.

CHINA. Guangxi: Nanning City, 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 GX201511068 ( HMAS–L 0138049), GX201511069 ( HMAS–L 0138048), GX201511070 ( HMAS–L 0138046), GX201511080 ( HMAS–L 0138053), GX201511084 ( HMAS–L 0138050), GX201511089 ( HMAS–L 0138051), GX201511094 ( HMAS–L 0138052). Yunnan: Xishuangbanna, Mengla County, tropical botanical garden of Chinese Academy of Sciences, East area. 21°55'39"N, 101°15'52"E, 560 m alt., on living leaves, 18 Nov 2015, X.L.Wei & S.H.Jiang XTBG2015038 ( HMAS–L 0138047).

Remarks.

Strigula antillarum can be distinguished from the new species by the perithecia being immersed only at base, aggregate and confluent pycnidia forming black spots or radiating lines, and bacillar, shorter, macroconidia (12-20 × 3-4 μm) with rounded ends ( Lücking 2008). The new species is externally most similar to Strigula smaragdula (Figure 2 e–i), in which perithecia are covered by the bright green thallus ( Santesson 1952, Lücking 2008). However, Strigula acuticonidiarum is characterized by a thinner thallus with entire to crenulate margins (thallus 20-80 μm thick in Strigula smaragdula ), the absence of distinct lobes, and in having small and round thalli instead. Anatomically, it differs in the shorter asci and the macroconidia having more acute ends. In molecular analyses, the ITS rDNA sequences confirmed it as different from Strigula smaragdula (Figure 1). The two species are distinct both morphologically and phylogenetically.

Strigula smaragdula is generally considered to be a very common but variable species, traditionally recognized morphologically, for example by the thallus having entire to crenulate or lobulate margins, and sometimes the whole thallus being lobate-lacin iate. This variation series has been regarded as merely due to environmental or habitat modification. However, the most common state, represented by the holotype of Strigula smaragdula , is characterised by distinct, but short and rounded marginal lobes ( Santesson 1952). The broad concept of Strigula smaragdula evidently represents a species complex, rather than a single species. Minor morphological traits, including thallus form and differences in ascus size and the shape of macroconidia, are diagnostic for segregating Strigula acuticonidiarum from Strigula smaragdula s. str., a distinction supported by molecular data (Figure 1).