Verrucaria elaeomelaena (A.Massalongo) Arnold

Schiavo, Lo, 2015, Revision of the Verrucaria elaeomelaena species complex and morphologically similar freshwater lichens (Verrucariaceae, Ascomycota), Phytotaxa 197 (3), pp. 161-185 : 175-176

Verrucaria elaeomelaena (A.Massalongo) Arnold [ V. elaeomelaena s.str.] ( Figs. 3 B–C )

Verh. Zool.-bot. Ges. Wien 18: 958 (1868).— Lithoicea elaeomelaena A.Massal. Atti Inst. Veneto Sci. lett., ed Arti, Sér. 3 (2): 380 (1856).

Type:— [ GERMANY, Bavaria:] ad saxa in Franconia, leg. Arnold (lectotype, designated by Swinscow 1968 TO!: isolectotypes BM!, FR!). — Epitype (selected here): GERMANY, Bavaria, Oberfranken, headwaters of small stream E of the village of Streitberg, 49°48’45.38’’N, 11°14’18.20’’E, Oct. 2003, H. Thüs W1545 [BM000734085] (BM!), GenBank accession no KM243241.

Prothallus whitish, smooth, thin to absent. Thallus greenish-grey to grey (shade forms), light to dark brown (more or less exposed sites), thin to moderately thick 20–115 μm, medulla not differentiated or forming a thin to thick (5–75 μm) black basal layer (often in specimens on limestone), subgelatinous with algal cells often arranged in vertical lines and air filled spaces around hyphae not visible in anatomical sections. Perithecia forming distinct projections in thin thalli, perithecia density 9–28 in an area of 25 mm 2, only little projecting in thick thalli, usually covered by a thin thallus mantle, involucrellum thin (17–25 μm), vertical extension variable, sometimes even in perithecia from the same thallus ranging from near apical to wide spreading and reaching the bottom of the thallus, algae in thalline mantle present throughout or thinning out to absent towards the ostiole, exciple width 210–320 μm, exciple base pale, periphyses (18) 20–25 (38) μm, asci pyriform to obovate 58–90 μm, ascospores (16.2) 20.9– 24.1 –27.3 (29.9) × (9.6) 11.0– 12.3 –16.2 μm, lenght/width ratio of ascospores (1.3) 1.7– 2.0 –2.3 (2.6) [67/6]. Halonate perispore present in some fresh collections. Pycnidia not detected.

Habitat and distribution: Sequenced specimens include lichens from submerged limestone rocks, and subaquatic (only temporarily submerged) siliceous rocks from near sea level to 495 m elevation from Wales and Germany, but this taxon is probably widespread in temperate areas of the world. Morphologically identical specimens were seen from Austria, Poland and North America. In Central Europe and the British Isles it is a typical species of springs and headwaters.At low elevations in Germany it is usually a rare species and populations are often small and geographically isolated from each other, which makes them vulnerable to local extinction by exposure to extended periods of desiccation as a result of climate change or excessive water extraction, physical alteration of springs and increased silting from nutrient enrichment or sediment intake from the catchment area. The type locality of Verrucaria teutoburgensis , a possible synonym of V. elaeomelaena s.str. is directly threatened by the expansion of a nearby quarry.

Typification: The lectotype specimen chosen by Swinscow (1968) has the exact outline of the individual thalli on the rock as the illustrated material in Fig. 1 and 2 on plate 5 of the protologue (Massalongo 1858) and we conclude that they are identical. The type locality is named as “Franconia” on the lectotype specimen label but more precise information is given in the protologue where a letter by Arnold is cited in which he specified the locality of the collection to be nearby the Franconian village of Streitberg. The epitype specimen was collected in October 2003 in a small nameless stream app. 1km east of Streitberg in the valley of the river Wiesent. The sampled locality is the closest permanent stream in the vicinity of the village Streitberg and has a rich population of V. elaeomelaena (together with V. aquatilis and V. praetermissa ). In the protologue the range of the ascospore length is cited as 18.3–52 μm. The exceptional maximum size is much larger than those in the spores observed in all studied isotype specimens. The protologue includes a plate and in the illustration of asci and ascospores of the type specimens document a rather low variation in ascospore size and it is likely that in fact the maximum length given in the protologue is a typographic error and should read 25 instead of 52 μm.

Figures

FIGURE 1. Systematic placement of Verrucaria elaeomelaena agg., V. funckii and morphologically similar taxa within the Verrucariaceae based on a multigene dataset (nuLSU, nuSSU, mtSSU and RPB1). Support values are reported above or below the branches (posterior probability [PP]/bootstrap value [BS]). Nodes with strong support (100% PP and BS) are indicated by a black dot on the branches. Only significant values (higher than 95% PP and higher than 70% BS) are shown on the figure. Capronia munkii and Capronia pilosella were used as an out group.

FIGURE 2. Phylogeny of taxa within the Verrucaria elaeomelaena agg. Most likely tree obtained with MrBayes based on ITS. Support values are reported above or below the branches (posterior probability [PP]/bootstrap value [BS]). Only significant values (higher than 95% PP and higher than 70% BS) are shown on the figure. Verrucaria nigrescens was used as an out group.

FIGURE 3. A. Cross-section of a perithecium of Verrucaria submersella (syntype BM). B. Cross-section of a perithecium of Verrucaria elaeomelaena (isolectotype BM). C. Thallus of Verrucaria elaeomelaena (isolectotype BM). D. Thallus of Verrucaria alpicola (lectotype B). E. Cross-section of a perithecium of Verrucaria alpicola (lectotype B). Scale bar: A, B, E = 50 μm; C–D = 5 mm.