{{Short description|Single-species lichen genus}} {{Use dmy dates|date=June 2025}} {{Use Oxford spelling|date=June 2025}} {{Speciesbox | image = Leifidium tenerum 103555098.jpg | image_caption = ''Leifidium tenerum'' | parent_authority = Wedin (1993) | taxon = Leifidium tenerum | authority = Wedin (1993) }}

'''''Leifidium''''' is a fungal genus the family Sphaerophoraceae. The genus is monotypic, containing the single species '''''Leifidium tenerum''''', a fruticose lichen.<ref name="CoL_5BV6"/> This lichen forms pale grey to whitish cushions made up of thin, flexible branches that divide repeatedly. It reproduces through small fruiting structures at branch tips that release powdery spore masses when mature. The species grows in diverse Southern Hemisphere environments, from cool rainforests to alpine areas, spanning from Chile and New Zealand to Australia and subantarctic islands.

==Taxonomy==

''Leifidium'' is a small lichen genus in the family Sphaerophoraceae. It was erected by Mats Wedin in 1993 on the back of a cladistic study that split the old catch-all genus ''Sphaerophorus'' into three, recognising ''Leifidium'' alongside ''Sphaerophorus'' in the strict sense (''sensu stricto'') and ''Bunodophoron''. The genus is monospecific: its type—and only—species is ''Leifidium tenerum''.<ref name="Wedin 1993"/> This lichen was originally described as ''Sphaerophorus tener'' by Laurer in 1827.<ref name="Laurer 1827"/> The genus is named in honour of the Swedish lichenologist Leif Tibell.<ref name="Hertel et al. 2017"/>

Phylogenetically, ''Leifidium'' groups most closely with ''Bunodophoron''; together they form a single branch within the family, united by a shared style of spore "icing" (a thin coating deposited after the spores leave the asci). ''Leifidium'' is set apart by a thin outer skin or cortex, and by branch-tip fruiting cups whose rigid rim ({{lichengloss|excipulum}}) stays intact until the spores mature, then pops off like a cap. Its spherical spores bear little surface ornamentation, and its asexual spores (conidia) are short, oval bodies—not the rod-shaped type seen in ''Bunodophoron''.<ref name="Wedin 1993"/>

==Description==

''Leifidium'' produces a pale grey-to-whitish thallus made up of very slender, round ({{lichengloss|terete}}) branches that divide repeatedly to form loose cushions or low mats on the substrate. Each branch is sheathed in an exceptionally thin {{lichengloss|cortex}} only about 30–45&nbsp;μm thick—just two or three cell layers—so the branches remain flexible and often appear translucent at the tips. Beneath this skin lies a dense medulla of tightly packed fungal threads (hyphae). The combination of a thread-like, cushion-forming habit and the wafer-thin cortex readily separates ''Leifidium'' from its close relative ''Bunodophoron'', whose branches are flatter and more thickly corticate.<ref name="Wedin 1993"/>

Reproductive structures sit at the very tips of stouter, upright side-branches. Each apothecium begins its development hidden beneath a cup-like wall ({{lichengloss|excipulum}}); when the spores are ripe this wall detaches in one piece "like lifting off a cap", exposing a powdery spore mass (the {{lichengloss|mazaedium}}) that faces upward. The spores themselves are tiny, almost smooth, globe-shaped bodies (6.5–8.5&nbsp;μm in diameter) that start colourless and become faintly bluish-grey in alkaline solutions; any delicate surface ornament quickly dissolves in chemical tests. Minute flask-shaped pycnidia dot the branch tips, lining them with branched filaments that bud off single-celled, broadly ellipsoidal conidia about 3–4 × 1.5–2&nbsp;μm. Chemical analyses show the presence of the compound sphaerophorin, together with minor, unidentified secondary metabolites.<ref name="Wedin 1993"/>

Although ''Leifidium'' is sometimes somewhat similar in appearance to certain species of ''Cladia'' or ''Cladonia'', it can be distinguished by its solid thallus, as those genera have hollow branch structures.<ref name="Kantvilas 2023"/>

==Habitat and distribution==

''Leifidium tenerum'' tolerates a broad range of Southern Hemisphere habitats, growing on alpine and subantarctic soil or rock as well as on the bark and twigs of trees, tree ferns, lianas and bamboo in cool-temperate rainforests. It is most vigorous in moist, well-lit sites; fertile branches become common at higher elevations and rainfall levels, while at low altitudes apothecia are typically produced beside spray zones near waterfalls. The species spans the southern temperate belt, from Cape Horn north to Temuco in Chile, through New Zealand, from Tasmania to central New South Wales in Australia, and across several subantarctic islands.<ref name="Wedin 1993"/>

==References== {{Reflist|refs=

<ref name="CoL_5BV6">{{Catalogue of Life |id=5BV6 |title=''Leifidium'' |access-date=29 June 2025}}</ref>

<ref name="Hertel et al. 2017">{{cite journal |first1=Hannes |last1=Hertel |first2=Georg |last2=Gärtner |first3=László |last3=Lőkös |title=Forscher an Österreichs Flechtenflora |trans-title=Investigators of Austria's lichen flora |journal=Stapfia |year=2017 |volume=104 |issue=2 |pages=1–211 (see pp.&nbsp;149–150) |language=German |url=https://www.zobodat.at/biografien/Flechtenforschung_Austria_STAPFIA_0104_2_0001-0211.pdf}}</ref>

<ref name="Kantvilas 2023">{{cite web |last1=Kantvilas |first1=G. |year=2023 |title=''Leifidium'' version 2023:1 |editor-first=M.F. de |editor-last=Salas |work=Flora of Tasmania Online |publisher=Tasmanian Herbarium, Tasmanian Museum and Art Gallery |location=Hobart |url=https://flora.tmag.tas.gov.au/lichen-genera/leifidium/ |access-date=29 June 2025}}</ref>

<ref name="Laurer 1827">{{cite journal |last=Laurer |first=F. |year=1827 |title=Sieber'sche Lichenen |journal=Linnaea |volume=2 |pages=38–46 |language=de |url=https://www.biodiversitylibrary.org/page/93989}}</ref>

<ref name="Wedin 1993">{{cite journal |last=Wedin |first=Mats |title=A phylogenetic analysis of the lichen family Sphaerophoraceae (Caliciales); a new generic classification and notes on character evolution |journal=Plant Systematics and Evolution |volume=187 |issue=1–4 |year=1993 |doi=10.1007/bf00994100 |pages=213–241 |bibcode=1993PSyEv.187..213W |url=https://www.researchgate.net/publication/225901310}}</ref>

}}

{{Taxonbar|from=Q6519492|from2=Q21274351}}

Category:Lecanorales Category:Taxa described in 1993 Category:Monotypic Lecanorales genera Category:Lichen genera Category:Taxa named by Mats Wedin