Heterodermia pindurae Eb. Fisch, Killmann, Ertz & Sérus., 2017

Fischer, Eberhard, Killmann, Dorothee, Ertz, Damien & Sérusiaux, Emmanuël, 2017, Heterodermia pindurae (Physciaceae) - a new foliose lichen from Rwanda, Phytotaxa 311 (3), pp. 277-282 : 277-281

Heterodermia pindurae Eb. Fisch, Killmann, Ertz & Sérus. sp. nov. ( Fig. 1 , 2 )

Type:— RWANDA. Nyungwe National Park, Rugenge Swamp c. 1.5 km S of Pindura along road to Bweyeye , 2211 m, S 02°28’48.3’’ E 29°13’41’’, Fischer, Killmann, Ertz & Sérusiaux 246/2005, 4. Apr. 2005 (holotype LG , isotype KOBL ).

The species differs from Heterodermia subcomosa and H. pellucida in the minute, only 0.3–0.6 cm long thallus, blackish cilia, lack of laciniae, the pedicellate, cup-like apothecia with sorediate margin at the end of all lobes and the production of norstictic acid.

Thallus minute, 0.3–0.6 cm long and 0.1–0.15 cm wide; lobes ascending, rounded to revolute, disjunct to imbricate, whitish at base and irregularly to dichotomously branched, margin with greyish to blackish rhizines, 0.8–1.5 mm long. Upper cortex about half of lobe thickness, lower side non-corticated, whitish. Lobes usually ending in a cup-like structure with expanded margin resembling a tulip covering an apothecium with densely sorediate margin; cup 0.9–1.2 mm long and 0.6–1.5 mm in diameter; inner side of the cup non-corticated, arachnoid; margin often asymmetrical, 1 mm wide.

Apothecia subapical, 0.7–0.9 mm in diameter, hidden in the rounded cup-like and hollow lobes, margin densely covered by soredia, 25–45 μm in diameter. Epihymenium greenish-brown, c. 15 μm high; hymenium almost colourless, c. 140 μm in diameter; hypothecium light brown, c. 60 μm in diameter, asci all immature, 120 × 8 μm, spores immature, c. 17 × 10 μm (all measurements in longitudinal section).

Chemistry: —Spot tests: Thallus K+ yellow, medulla K+ yellow, C-, KC+ yellow, PD + yellow. Secondary metabolites: Traces of norstictic acid, atranorin and zeorin.

Habitat and distribution: —The species is so far known from Rwanda (Nyungwe National Park and Volcanoes National Park) in the Albertine Rift (East Africa), where it is colonizing the outermost and thin twigs of Hypericum revolutum , in open swamp vegetation between elevations of 2211 to 3000 m. The type locality ( Fig. 2 ) situated in Nyungwe National Park, which is one of the most diverse montane forests in East Africa ( Ewango 2001, Fischer et al. 2003, Fischer & Killmann 2008), comprises Alchemilla ellenbeckii Engl. , Anagallis angustiloba (Engl.) Engl. , Begonia meyeri-johannis Engl. , Brillantaisia owariensis P.Beauv. , Coelachne africana Pilg. , Cyperus denudatus L.f., Cyperus nigricans Steud. , Epipactis africana Rendle , Eulophia horsfallii (Batemann) Summerh. , Hypericum revolutum Vahl , Impatiens mildbraedii Gilg. , Lobelia mildbraedii Engl. , Lychnis kiwuensis (T.C.E.Fr.) M.Popp , Osmunda regalis L., Hypericum revolutum Vahl, Rapanaea melanophloeos (L.) Mez., and Satyrium crassicaule Rendle.

Comparison to similar species:— The new taxon belongs to the Heterodermia comosa -group ( Moberg 2011, Mongkolsuk et al. 2015) which is characterized by foliose to subfruticose thallus with typically ascending, spathulate or paddle-shaped lobes and white marginal cilia. This group corresponds to the series 4 Podocarpae ( Kurokawa 1962). The new species is morphologically similar to Heterodermia subcomosa (Nyl.) Trass (1992: 20) ( Physcia leucomelaena var. subcomosa Nyl., Nylander 1860: 415 ) ( Fig. 3 ) and Heterodermia pellucida (D.D. Awasthi) D.D. Awasthi ( Awasthi 1973: 114) ( Anaptychia pellucida D.D. Awasthi 1957: 136 ) ( Fig. 3 ), but differs in having small (0.3–0.6 cm) thallus, blackish cilia, lacking laciniae, pedicellate, cup-like apothecia with sorediate margin at the end of lobes and presence of norstictic acid ( Table 1 ). Heterodermia podocarpa (Bél.) D.D.Awashti (1973: 114) ( Parmelia podocarpa Bél., Bélanger 1840: 122 ), a species also known from East Africa containing norstictic acid ( Moberg 2011), differs from the new taxon in the larger thallus (up to 5 cm broad) and the size and shape of the apothecia. Two other members of the Heterodermia comosa -group, viz. H. archeri Elix (2011: 16) from Australia and H. galactophylla (Tuck.) W.L.Culb. ( Culberson 1966: 482) ( Parmelia ciliaris b. galactophylla Tuck., Tuckermann 1847: 224 ) from North and South America differs distinctly from the new taxon in the size and the shape of the thallus which is up to 5 cm broad and lacking apothecia.

Paratypes:— RWANDA. Nyungwe National Park, Rugenge Swamp c. 1.5 km S of Pindura along road to Bweyeye , 2211 m, S 02°28’48.3’’ E 29°13’41’’, Fischer s.n., Apr. 2006 KOBL ); ibid., March 2008 ( KOBL) ; Nyungwe, swamp at Richard Kandt’s source of the Nile, Rukarara River near Rugege , 2450 m, S 2°21’31.2” E 29°22’04.5”, Fischer & Killmann s.n., 22 Sept. 2015 ( KOBL) ; Volcanoes National Park, Hagenia-Hypericum forest near former Karisoke Research Station , open swamp, on branches of Hypericum revolutum, Killmann & Fischer s.n., 14 March 2010 ( KOBL) .

Figures

FIGURE 1. Heterodermia pindurae. A–B. Thallus. C–E. Details of apothecia. F. Section through apothecium. All from the holotype.

FIGURE 2. Heterodermia pindurae. A–B. Thallus. C–E. Type locality Rugenge swamp in Nyungwe National Park, Rwanda. Photo. E. Fischer & D. Killmann.

FIGURE 3. A–B. Heterodermia pellucida (Awashti 3894). C–F. Heterodermia subcomosa (Cleef 6610).