{{Short description|Species of lichen-forming fungus}} {{Use mdy dates|date=February 2026}} {{Use American English|date=February 2026}} {{Speciesbox | image = | image_caption = | taxon = Gyalectidium barbatum | authority = Herrera‑Camp. & [[Robert Lücking|Lücking]] (2002) }}

'''''Gyalectidium barbatum''''' is a [[foliicolous lichen|foliicolous]] (leaf‑dwelling) [[crustose lichen]] in the family [[Gomphillaceae]],<ref name="CoL_3HNNG"/> described from specimens collected in [[Veracruz]], Mexico. It is distinguished from related species by its {{lichengloss|hyphophores}} (minute [[asexual reproduction|asexual reproductive]] structures) and [[ascospore]] size range.

==Taxonomy== The species was [[species description|described]] as new to science by María de los Ángeles Herrera-Campos and [[Robert Lücking]] in 2002 from material collected from the [[Los Tuxtlas Biosphere Reserve]]; the [[holotype]] is deposited at MEXU (voucher: Herrera‑Campos et al. 153). The original description emphasises diagnostic hyphophore morphology and spore dimensions separating it from others in ''[[Gyalectidium]]''.<ref name="Herrera‑Campos & Lücking 2002"/>

==Description== ''Gyalectidium barbatum'' is a leaf-dwelling crust that grows on the upper surface of living leaves, forming tiny whitish to silvery-gray patches. The thallus is slightly swollen in appearance because it is encrusted with [[calcium oxalate]] crystals; individual patches are about 0.5–1&nbsp;mm wide. The [[photosynthesis|photosynthetic]] partner ({{lichengloss|photobiont}}) is a [[green alga]] in the genus ''[[Trebouxia]]'', with roughly spherical cells measuring about 5–8&nbsp;[[μm]] in diameter. <ref name="Herrera‑Campos & Lücking 2002"/>

The species is characterized by abundant marginal hyphophores ([[asexual reproduction|asexual reproductive]] structures). These are horizontal, closely {{lichengloss|appressed}}, broadly triangular to irregularly cut (giving a "shaggy" outline), and translucent overall but darker near the base. Each scale is about 0.05–0.15&nbsp;mm long and about 0.15–0.3&nbsp;mm wide at the base. Beneath the scale bases, the lichen produces a single "bunch" of short, bead-like ({{lichengloss|moniliform}}) [[hypha]]e that branch in a star-like pattern and are mixed with algal cells. The hyphal segments are roughly sausage-shaped, and measure about 4–7&nbsp;×&nbsp;1.8–2.2&nbsp;μm. [[Apothecia]] appear to be uncommon (only one was reported), and it was said to resemble those of closely related species such as ''[[Gyalectidium caucasicum|G.&nbsp;caucasicum]]'' and ''[[Gyalectidium minus|G.&nbsp;minus]]''.<ref name="Herrera‑Campos & Lücking 2002"/>

==Habitat and distribution== The [[type (biology)|type]] collection of ''Gyalectidium barbatum'' was made at the Los Tuxtlas Tropical Biology Station in Veracruz, Mexico, within the Los Tuxtlas Biosphere Reserve. The authors describe the area as [[tropical]] moist [[broadleaf forest]] (lowland [[rainforest]]), and the specimen was collected at about {{cvt|150|–|250|m}} elevation. As of its original description, it was known only from the [[type locality (biology)|type locality]] in Veracruz.<ref name="Herrera‑Campos & Lücking 2002"/>

==References== <references>

<ref name="CoL_3HNNG">{{Catalogue of Life |id=3HNNG |title=''Gyalectidium barbatum'' Herrera-Camp. & Lücking |access-date=February 2, 2026}}</ref>

<ref name="Herrera‑Campos & Lücking 2002">{{cite journal |last1=Herrera‑Campos |first1=M.A. |last2=Lücking |first2=R. |year=2002 |title=The foliicolous lichen flora of Mexico. I. New species from Los Tuxtlas Tropical Biology Station, Veracruz |journal=The Lichenologist |volume=34 |issue=3 |pages=211–222 |doi=10.1006/lich.2002.0397}}</ref>

</references>

{{Taxonbar|from=Q17388218}}

[[Category:Gyalectidium|barbatum]] [[Category:Lichen species]] [[Category:Lichens described in 2002]] [[Category:Lichens of Mexico]] [[Category:Taxa named by Robert Lücking]]