Ochrolechia trochophora (Vain.) Oshio var. trochophora

Ochrolechia trochophora (Vain.) Oshio var. trochophora View in CoL View at ENA

Fig. 7 View Figure 7

Remark.

J. Sci. Hiroshima Univ., Ser. B, Div. 2 (12): 145 (1968). – Pertusaria trochophora Vain. View in CoL , Bot. Mag. ( Tokyo) 32: 155 (1918).

Type.

Japan • Prov. Kozuke, Mt. Akagi. Ad corticem arboris, Yasuda 53 ( TUR-V–7255 – holotype, not seen; see Brodo (1991: 762); TI – isotype, not seen; see ( Oshio 1968: 145)).

Description.

Thallus greyish-white to greyish-green, thin, verruculose, dull; isidia absent, prothallus indistinct, soredia greyish-white.

Sexual morph. Apothecia frequent, scattered, sessile, ellipsoid or round, 1.1–1.8 mm diam.; disc pale pink, plane to lightly rugose, epruinose, with a hazy white film; margin smooth or verruculose, higher than disc, dull, concolorous with the thallus. Pycnidia are absent. Hymenium hyaline and colourless, 380–392 μm high; epihymenium brown, 20–28 μm high; hypothecium greyish-brown (the colour of the epihymenium and hypothecium partially or completely disappears in a 10 % KOH solution), 10–17 μm high; coccoid green alga, algae absent or spotty in the margin and continuous below the hypothecium. Asci clavate, 8 - spored, (359) 363–372 (375) × (42) 43–49 (52) μm. Ascospores hyaline, aseptate, broadly ellipsoid, (50) 55–70 (75) × (22) 23–26 (28) μm (n = 30).

Chemistry.

Thallus contains gyrophoric acid, lecanoric acid and atranorin; ascomata contain gyrophoric acid and lecanoric acid. ( TLC). soredia: K + yellow-green, C –, KC –; thallus cortex: K + yellow, C + red, KC + red to yellow-green; medulla: C –; apothecia cortex: K + yellow, C + red, KC + red to yellow-green; medulla: C –; disc: C + red; thallus UV –.

Material examined.

China • Guizhou Province, Zunyi City, Kuankoshui National Nature Reserve , 28°12'29.34"N, 107°10'24.27"E, 1418 m elev., on bark, 18 November, 2023, Weiwei Zheng and Bo Liu, KKS 150-2 ( KUN-L 96625 ) GoogleMaps .

Notes.

Ochrolechia trochophora is a widely distributed species reported from several locations worldwide. It is primarily characterised by verruculose apothecial margins lacking or containing scattered algal cells. The key distinction between O. trochophora var. trochophora and O. trochophora var. pruinirosella lies in the fact that the latter has a pruinose apothecial disc and the vast majority of its specimens contain variolaric acid. In contrast, O. trochophora var. trochophora occasionally exhibits a hazy white film on the disc, but this is not pruina and very few specimens contain variolaric acid or atranorin ( Brodo 1991). As reported by Kukwa (2009), European and Turkish specimens of O. trochophora var. trochophora possess a relatively thin thallus. Furthermore, the detection of atranorin in one Chinese specimen aligns with these findings. Collectively, this evidence supports the identification of specimen KKS 150-2 as O. trochophora var. trochophora .

The specimen also bears soredia, which is a relatively distinctive variation, as according to previous reports, no records of soredia have been documented in O. trochophora (whether the typical variety or other known varieties) ( Brodo 1991; Kukwa 2009). This indicates that O. trochophora might be morphologically more variable than previously thought.

In Ochrolechia , many species (e. g. O. africana , O. antillarum , O. gowardii , O. trochophora ) contain small crystalline structures in the apothecial medulla ( Brodo 1991). In the species we describe, the brownish appearance of both the epihymenium and hypothecium in apothecial sections is more likely a structural colour rather than a pigment-based one. This conclusion is primarily based on the partial or complete fading of the brown colour when treated with 10 % KOH, likely due to the dissolution of abundant granular or crystalline substances in the tissues.

Traditionally, the classification of species within the genus Ochrolechia has primarily relied on a combined analysis of morphological characteristics and chemical compounds. Morphologically, key diagnostic features include thallus thickness, the presence or absence of isidia and soredia, apothecial morphology, hymenium height, spore size and the position of the algal layer. Chemically, species in this genus exhibit a remarkable diversity of secondary metabolites, which serve as critical taxonomic markers. These compounds mainly belong to the following classes: Orcinol depsides (e. g. gyrophoric acid, lecanoric acid and olivetoric acid), orcinol depsidones (e. g. variolaric acid and alectoronic acid), higher aliphatic acids (e. g. lichesterinic acids, protolichesterinic acids and murolic acids) and xanthones, which can induce yellow fluorescence in the thallus under long-wave ultraviolet light. Additionally, trace amounts of atranorin have been detected in some species ( Brodo 1991; Kukwa 2009).

In our study, thin-layer chromatography revealed significant levels of the lichen secondary metabolite atranorin in both the newly-described species O. leigongshanensis and the known species O. trochophora var. trochophora . This finding contrasts with the previous understanding that atranorin exists only in trace amounts within the genus Ochrolechia . Notably, these two species share a key morphological characteristic, the presence of soredia. The combination of this chemical and morphological feature provides valuable new insights into the evolutionary relationships within Ochrolechia .

Soredia are rarely observed in Ochrolechia and atranorin is not usually a major metabolite in this genus. The discovery that both O. leigongshanensis and O. trochophora var. trochophora possess these two characteristics strongly suggests that they may belong to a distinct phylogenetic lineage previously unrecognised. The production of soredia, as an asexual reproductive structure, is linked to specific genotypes, while the substantial synthesis of atranorin indicates the activation of particular biochemical pathways. The stable co-existence of these two independent traits, both morphological and chemical, within a limited taxonomic group is unlikely to be coincidental and likely represents synapomorphies inherited from a common ancestor. Thus, we hypothesise that these two species may share a most recent common ancestor within Ochrolechia , potentially forming a monophyletic group.

With the rapid advancement of molecular techniques, phylogenetic analysis has become an indispensable tool in species identification and evolutionary studies. Molecular data provide objective genetic evidence that enables the effective differentiation of morphologically similar and cryptic species, clarifying taxonomic uncertainties, such as synonymy and facilitating the discovery of new taxa ( Spatafora et al. 2006; Miadlikowska et al. 2014). Relying solely on phenotypic characteristics often fails to resolve taxonomic ambiguities, as these features are influenced by environmental factors and developmental stages. In contrast, genetic data offer greater stability. Therefore, this study adopts an integrative taxonomic approach, combining phylogenetic analysis, morphological examination and chemical profiling to provide a comprehensive and accurate classification of new Ochrolechia species.

The phylogenetic analysis in this study revealed that all newly-described species form a single clade (Fig. 1 View Figure 1 ). Although bootstrap support for some branches within this clade was relatively low (<70 %), we interpret this not to ambiguous taxon delimitation, but rather to the substantial genetic distances amongst these new species or it might be due to the insufficient sampling in this clade. As more sequences of Ochrolechia species are published in the future, the topology may become more stable. Such considerable interspecific genetic divergence may result in a higher number of ambiguous alignment sites, leading to reduced nodal support in phylogenetic reconstructions. This phenomenon strongly suggests that the present study may have only uncovered a fraction of the diversity within the genus Ochrolechia in Guizhou, China. Limitations in sampling scope and specimen numbers currently hinder a full assessment of the true morphological variation and geographical distribution ranges of these species, which may also contribute to the temporarily unresolved phylogenetic relationships.

It is important to note that, while molecular support could be further strengthened through additional gene loci or expanded sampling in the future, all new species described in this study exhibit unique combinations of morphological and chemical characteristics, enabling clear distinction from all known related species.

In conclusion, the distinct clade formed by the new species described in this study not only enhances our understanding of the phylogenetic framework of Ochrolechia , but also highlights significant genetic variation within the clade, suggesting that the region may harbour an underexplored diversity of Ochrolechia . Future studies should prioritise more extensive and systematic specimen collection from this region and neighbouring areas, combined with multi-locus genomic data, to thoroughly elucidate the speciation mechanisms and the broader diversity of this genus.