Siphula paramensis V. Marcano & L. Castillo, 2021

Marcano, Vicente, 2021, Siphula paramensis V. Marcano & L. Castillo (Icmadophilaceae, Lichenized Fungi), a new species from the high paramo in Venezuela, Phytotaxa 512 (3), pp. 169-178 : 170-176

Siphula paramensis V. Marcano & L. Castillo sp. nov.; MycoBank MB #838831 ( Figs. 1–4 )

Thallus parvus, ochraceus vel cinereus, lobis pyriformibus, integribus, minutis (usque ad 1.25 mm altis et 0.8 mm latis), apicibus rotundis, rasilibus, acida baeomycesicum squamaticumque in medulla continens.

Type: — VENEZUELA, Merida, Sierra Nevada, Los Chorros valley , 4400 m a.s.l., (8°37’55ˮN, 70°58’37ˮW), 24 January 2021, V. Marcano, L. Castillo & D. Abreu 21–65 (holotype MER, isotype herb. V. Marcano private) .

Thallus quite small, compressed, forming small mats (up to 10 cm), with the basal parts forming a long, tubular, dark brown stalk (0.5–0.6 mm wide) with a developed rooting system. Lobes erect, occasionally divided 2 or 3 times, discrete or more or less fused, narrowly obovoid with a tapering base or globuliform, (0.4–)0.6–0.8(–1) mm wide, 0.9–1.25 mm tall. Surface ochre-coloured, yellowish or whitish gray (in older thalli), smooth at the margins. Apices rounded, sometimes flat, entire, not eroded, frequently rugose, usually with reticulate lines ( Fig. 4 ), radially uniform, occasionally thickened, having yellowish spots. Cortex 20–30(–40) μm thick, distinct, not interrupted; algal layer (30–)40–80(–100) μm thick, continuous; medulla white, compact, 500–670 μm wide; medullary hyphae 2–3 μm thick, thin-walled, straight, hyaline; photobiont cells ± spherical, 8–13(–16) μm diam. Rhizines dark brown, strand-like and flattened, frequently fused, 0.15–0.2 mm at the point of attachment, 0.4–0.5 cm long.

Chemistry: TLC, HPTLC: baeomycesic and squamatic acids (n = 9; V. Marcano & L. Castillo 21–65; V. Marcano, L. Castillo & D. Abreu 21–66, 21–67; V. Marcano & R. Vidal 4997); cortex K-, C + yellow, and P + yellow; medulla K-, C-, and P- (n = 12). The compounds are present in relatively high amounts, and they appear to be concentrated in the cortex. Individual thalli within a single population exhibit different concentrations of secondary compounds. Hence, the intensity of spots tests is generally unpredictable (Marcano 2021). The lobes have inconstant coloration, varying between whitish gray and yellowish or ochre-coloured spots in the apices ( Fig. 2A, B ), presumably due to variable concentrations of secondary compounds.

Ecology and distribution: Siphula paramensis is a rare species known only from the type locality and from the Mifafi paramo at the Sierra La Culata (8°51’05ˮN, 70°56’40ˮW), Venezuelan Andes. In the Sierra Nevada at Los Chorros valley it is relatively abundant whereas in the Mifafi paramo it is apparently uncommon. It grows on mossy soil over exposed granitic rocks and eroded, steep moraine slopes in paramo, at an elevation of 3800–4400 m ( Fig. 5 ). This is the Siphula species that grows at the highest altitude in Venezuela ( Lopez-Figueiras 1986, Kantvilas & Elix 2002, Marcano 2021). The site in the Sierra Nevada at Los Chorros valley supports a shrub vegetation with scattered, populations (chirrivitales) of native trees, such as Polylepis sericea Weddell (Rosaceae) , Escallonia tortuosa Kunth (Escalloniaceae) , with abundant mosses and lichens on the steep slopes, and extensive cushions in seasonally inundated sites consisting of Arenaria jahnii S.F. Blake [= Arenaria venezuelana (S.F. Blake) Stey ] and Aciachne pulvinata Bentham ( Fig. 6 ). This locality is characterized by low mean temperatures (5–8°C), a humid climate and high annual precipitation (1160 mm). By contrast, the Mifafi paramo represents an alpine desert vegetation, with Coespeletia timotensis (Cuatrecasas) Cuatrecasas and C. lutescens (Cuatrecasas & Aristeguieta) Cuatrecasas which are the trees (up to 7 m tall) that grow at the highest altitude in the Venezuelan Andes. The climate is drier than at the Sierra Nevada and has a lower mean temperature (0.4–5°C) and annual precipitation (650 mm). It also receives more UV irradiation, as altitudinal distribution of effective global UV-irradiance in the Venezuelan Andes shows an increment of 150 J m –2 per 100 m, and values of 2.15–2.20 kJ m – 2 in the studied localities ( Marcano et al. 2009, 2010a,b).

Remarks: Siphula paramensis is characterized by its very small thallus, ochre-coloured, yellowish or whitish surface (in older thalli), obovoid or globuliform lobes, rugose, rounded, entire apices ( Fig. 2A, B ) exhibiting reticulated lines ( Fig. 4 ), dark brown rhizines and the presence of baeomycesic and squamatic acids. Siphula paramensis closely resembles S. subsimplex , a species recently described from the Guayana Highlands which is considered to be endemic to Chimanta Massif (Marcano 2021). This latter is readily distinguished by erect, terete lobes, the concave, truncate or eroded apices depending on the age of the specimens, the secondary, erect, more or less terete divisions occasionally emerging from the apices ( Fig. 2C, D ; see Marcano 2021, Fig. 1C ), thicker cortex (70–120 μm thick), larger rhizines (0.8–1.2 cm), and squamatic acid and an unidentified substance. The lobes in S. paramensis are slightly shorter but wider than in S. subsimplex and lack apical divisions. Moreover, S. subsimplex grows on mossy quarzitic rocks in seasonally inundated sites at 2350–2800 m whereas S. paramensis occurs on steep granitic slopes at high elevations (≥ 3800 m). Siphula paramensis is also very similar to S. verrucigera (J.M. Gmelin 1791: 1377) R. Sant. in Almborn (1966: 84). Both contain baeomycesic and squamatic acids, but the latter has a stalked, decumbent thallus, truncate apices, and is known only from South Africa (Kantvilas 2002). Squamatic and baeomycesic acids are present together in S. subteruloides and S. fastigiata among the Venezuelan Siphula species.

Biogeographic evidence suggests that S. paramensis has evolved after the uplift of the northern termination of the Andes, which occurred during the Pliocene-Pleistocene periods ( Kohn et al. 1984), while S. subsimplex may have evolved after the tepuian uplift which is supposed to have taken place about 70 Mya at the end of the Cretaceous period ( Briceño et al. 1991, Gibbs & Barron 1993, Marcano 2021). Thus the geographical distribution of the S. paramensis-S. subsimplex complex seems to be an example of biogeographical vicariance. However, molecular studies are necessary in order to determine the position of these taxa in the Siphula clade.

Usnic acid (dibenzofurane derivative) and atranorin (depside) are often found in the cortex of lichen species ( White & James 1985, Marcano et al. 1999, Truong et al. 2011). Their presence is easily recognized by a yellow-green or pale gray thallus color. However, they are sometimes present in such low quantities that they are undetectable by TLC and HPTLC (Marcano et al. 2021). The yellowish or ochre-coloured thalli of S. paramensis may suggest the presence of usnic acid, but they appear to contain only baeomycesic and squamatic acids by TLC and HPTLC. It is observed that the yellowish coloration is most notable when the species is exposed in its habitat to a higher intensity of irradiation. In the genus Siphula , a yellowish coloration is rare and has been observed in one species only, S. flavovirens Kantvilas, Zedda & Elix (2003: 22) containing usnic acid and caloploicin.

The presence of the baeomycesic and squamatic acids in S. paramensis may suggests a highly efficient UVscreening role at the UVA and UVB region and a selective advantage ( Culberson & Culberson 1970, Rundel 1978, Rogers 1989, Marcano 2010a,b). UV-screening capacity of baeomycesic and squamatic acids in S. paramensis would be influenced by the amounts of this substance synthesized in the thallus. Variation in concentrations of secondary compounds in the Siphula taxa ( Kantvilas & Elix 2002, Marcano 2021) can be difficult to interpret either as the result of genetic variations or as the result of environmental truncation of biosynthesis pathways ( Rogers 1989). However, the distribution of baeomycesic and squamatic acids in S. paramensis reveals it is able to produce a group of substances which appear be typically dependent to the ecology where the species occurs.

Etymology: The epithet refers to the ecological region where the type specimens were collected.

Additional specimens examined: VENEZUELA: Merida: Sierra La Culata, Páramo Mifafi, on granitic rocks, at 4400 m a.s.l., 16 march 1993, V. Marcano & R. Vidal 4997 ( MERF); Sierra Nevada, Los Chorros valley , on mossy in eroded, steep moraine slopes, 3800 m a.s.l., 24 January 2021, V. Marcano, L. Castillo & D. Abreu 21–66, 21–67, 21–68; on mossy, steep granitic slopes 3850 m, 31 March 2021, V. Marcano 21–315, 316 ( MER, herb. V. Marcano private) .

Figures

FIGURE 1. Habit of Siphula paramensis (V. Marcano, L. Castillo & D. Abreu 21–65 holotype); scale = 0.6 cm.

FIGURE 2. Comparative details of lobes in Siphula paramensis (A and B) and S. subsimplex (C and D). A–B. Specimens exhibiting rounded, rugose, entire apices (V. Marcano, L. Castillo & D. Abreu 21–65, holotype); scale = 0.6 mm. C–D. Secondary, erect, more or less terete divisions emerging from the apices (V. Marcano CHU–28–05, holotype); C, scale 0.4 mm; D, scale = 0.5 mm.

FIGURE 3. Comparison of cross sections in Siphula paramensis (A and B) and S. subsimplex (C and D). A–B. Specimens showing thin cortex, continuous algal layer and compact medulla (V. Marcano, L. Castillo & D. Abreu 21–65 holotype); A, scale = 0.3 mm; B, scale = 0.4 mm. C–D. Thicker cortex, algal layer sometimes interrupted, and compact medulla with cells occasionally interspersed (V. Marcano CHU-28-05 holotype); scales = 0.4 mm.

FIGURE 4. Rugose surface in the apices of Siphula paramensis exhibiting reticulated lines (V. Marcano, L. Castillo & D. Abreu 21–65 holotype); A, scale = 167 μm; B, scale = 80 μm.

FIGURE 5. Characteristic substrate of Siphula paramensis growing on exposed, granitic rock surfaces in steep slope, Paramo Los Chorros valley, Sierra Nevada de Mérida, Venezuelan Andes.

FIGURE 6. Typical habitat of Siphula paramensis on the Sierra Nevada de Merida at the Venezuelan Andes, 3800 m. A. Paramo Los Chorros valley. B. Steep moraine slope. Arrows indicate the site of the populations.