{{Short description|Genus of lichens}} {{Use dmy dates|date=August 2024}} {{Automatic taxobox | image = | taxon = Siphulastrum | authority = Müll.Arg. (1889) | type_species = ''Siphulastrum triste'' | type_species_authority = Müll.Arg. (1889) | subdivision_ranks = Species | subdivision = ''S. cladinoides''<br /> ''S. granulatum''<br /> ''S. mamillatum''<br /> ''S. triste''<br /> ''S. usneoides'' }}
'''''Siphulastrum''''' is a genus of lichen-forming fungi in the family Pannariaceae.<ref name="Wijayawardene et al. 2022"/> It has five species.<ref name="CoL"/> The genus was circumscribed by Johannes Müller Argoviensis in 1889, with ''S. triste'' assigned as the type species.<ref name="Müller 1889"/>
==Description==
The genus ''Siphulastrum'' comprises lichens that have a small, leaf-like ({{lichengloss|foliose}}) to scale-like ({{lichengloss|squamulose}}) thallus, which can be either smooth or covered with tiny bumps and warty projections. In some species, these features are so densely packed that they form tufted mats. The upper surface of the thallus varies in colour from yellowish-brown to grey-brown or even blackened and is often covered with fine, hair-like structures. The underside lacks a protective layer ({{lichengloss|ecorticate}}) and is pale brown, attaching to the {{lichengloss|substrate}} through root-like structures called {{lichengloss|rhizohyphae}}, which can be white to blue-black in colour. The lichen has a cyanobacterial photobiont (a photosynthetic partner), specifically from the genus ''Scytonema'', with cells arranged in chains.<ref name="Kantvilas 2023"/>
''Siphulastrum'' produces its reproductive structures in the form of apothecia, which are cup-shaped and lack a rim made from the thallus ({{lichengloss|biatorine}}). The {{lichengloss|disc}} of the apothecia is initially red-brown but soon turns black. The outer layer of the apothecia ({{lichengloss|proper exciple}}) is thin and persists as the lichen matures. It starts pale red-brown but eventually becomes the same colour as the disc, made up of radiating, tightly packed fungal filaments. The layer beneath the apothecia ({{lichengloss|hypothecium}}) ranges from pale to deep yellow-brown and intensifies in colour when treated with potassium hydroxide solution (K).<ref name="Kantvilas 2023"/>
The hymenium, the spore-producing layer, is partially amyloid, meaning it reacts with iodine, turning red (I+) and blue (KI+). This layer is mostly colourless (hyaline) but is covered by a greyish upper layer ({{lichengloss|epithecium}}). The filaments within the hymenium (paraphyses) are simple and relatively thick, measuring 3–4 μm in width, with slightly enlarged and often pigmented tips.<ref name="Kantvilas 2023"/>
The asci, which are the cells that produce spores, are club-shaped and contain eight spores. They have a unique ''Siphulastrum''-type structure, with a thin outer wall that turns intensely blue when treated with iodine (KI+), and a well-developed inner part ({{lichengloss|tholus}}) that lacks internal structures. The spores are simple, colourless (hyaline), and ellipsoid, typically with a roughened outer layer about 1 μm thick.<ref name="Kantvilas 2023"/>
The chemical composition of ''Siphulastrum'' includes argopsin, a secondary metabolite (lichen product) found in some lichens.<ref name="Kantvilas 2023"/>
While ''Siphulastrum'' is similar to some other taxa in the Pannariaceae, such as some ''Pannaria'' species, ''Fuscopannaria'', and ''Parmeliella'', it can typically be identified by a unique combination of features. These include the presence of argopsin in its thallus (which turns orange when tested with paraphenylenediamine), its partnership with ''Scytonema'' algae (rather than ''Nostoc''), its disc-shaped apothecia without a defined rim, and its distinctive spore-producing sacs that partially react with iodine.<ref name="Kantvilas 2023"/>
==Habitat and distribution== The species of ''Siphulastrum'' are confined to cold regions of the Southern Hemisphere. They have been found growing on bark or among epiphytic bryophytes, in thin soil amid bryophytes on boulders, and occasionally on peat-rich soil in sheltered microhabitats.<ref name="Kantvilas 2023"/>
==Species==
* ''Siphulastrum cladinoides'' {{au|C.W.Dodge (1948)}}<ref name="Dodge 1948"/> * ''Siphulastrum granulatum'' {{au|P.M.Jørg. & D.J.Galloway (1992)}}<ref name="Jørgensen & Galloway 1992"/> – Tasmania * ''Siphulastrum mamillatum'' {{au|(Hook.f. & Taylor) D.J.Galloway (1983)}}<ref name="Galloway 1983"/> – Tasmania; New Zealand; southern South America * ''Siphulastrum triste'' {{au|Müll.Arg. (1889)}}<ref name="Müller 1889"/> * ''Siphulastrum usneoides'' {{au|C.W.Dodge (1948)}}<ref name="Dodge 1948"/>
==References== {{Reflist|colwidth=30em|refs=
<ref name="CoL">{{Catalogue of Life |id=CF42B |title=''Siphulastrum'' |access-date=27 August 2024}}</ref>
<ref name="Dodge 1948">{{cite journal |last=Dodge |first=C.W. |year=1948 |title=Lichens and lichen parasites |journal=British Australian and New Zealand Antarctic Research Expedition Scientific Reports |volume=7 |page=69}}</ref>
<ref name="Galloway 1983">{{cite journal |last=Galloway |first=D.J. |year=1983 |title=New taxa in the New Zealand lichen flora |journal=New Zealand Journal of Botany |volume=21 |issue=2 |pages=191–199 |doi=10.1080/0028825X.1983|doi-broken-date=12 July 2025 }}</ref>
<ref name="Jørgensen & Galloway 1992">{{cite book |last1=Jørgensen |first1=P.M. |last2=Galloway |first2=D.J. |year=1992 |chapter=Pannariaceae |title=Lichens—Introduction, Lecanorales |series=Flora of Australia |volume=54 |pages=314–317 |isbn=978-0-644-24061-1}}</ref>
<ref name="Kantvilas 2023">{{cite web |authorlink=Gintaras Kantvilas |last=Kantvilas |first=G. |year=2023 |title=''Siphulastrum'', version 2023:1 |editor-first=M.F. |editor-last=de Salas |work=Flora of Tasmania Online |publisher=Tasmanian Herbarium, Tasmanian Museum and Art Gallery |location=Hobart |url=https://flora.tmag.tas.gov.au/pdf/Siphulastrum_2023_1.pdf}}</ref>
<ref name="Müller 1889">{{cite journal |last=Müller |first=J. |year=1889 |title=Lichenologische Beiträge XXXI |journal=Flora |volume=72 |pages=142–147 |language=la |url=https://www.biodiversitylibrary.org/page/71209}}</ref>
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Category:Pannariaceae Category:Peltigerales genera Category:Lichen genera Category:Taxa described in 1889 Category:Taxa named by Johannes Müller Argoviensis