Halecania

''Halecania'' is a genus of fungi in the family Leprocaulaceae. It has 24 species. These lichens form inconspicuous, crust-like films that spread over rock or other surfaces, with colours ranging from chalky white through bluish-grey to brownish-grey and textures that can be cracked like dried mud, granular, or covered in tiny warts. They reproduce through small, disc-shaped fruiting bodies that contain eight colourless ascospores divided by a single cross-wall, with the spore envelope swelling conspicuously when treated with certain chemicals—a key identifying feature.

Taxonomy

The genus was circumscribed by the Austrian lichenologist Michaela Mayrhofer in 1987, with '' Halecania alpivaga'' assigned as the type species. She created ''Halecania'' to contain species, formerly placed in '' Lecania'', with the following characteristics: uniformly amyloid apical domes, paraphyses with dark brown apical caps, and halonate ascospores (i.e., surrounded by a transparent coat).

Description

''Halecania'' species form a crustose (firmly attached, crust-like) thallus that spreads as an inconspicuous film over the substrate. The surface can be cracked like dried mud, coarsely , or covered in tiny warts, and its colour ranges from chalky white through bluish-grey to brownish-grey. A true —a protective skin of tightly packed cells—is either very thin or only partially developed; its outermost cells often carry a small brown cap that helps the lichen withstand intense light. Beneath this, the medulla (the inner tissue) shows no reaction to iodine (I–), and green, single-celled algae of the type supply the photosynthetic partner.

Sexual reproduction occurs in sessile apothecia (stalkless disc-shaped fruit-bodies) that are initially ringed by a rim of thallus tissue (the ); this rim soon erodes, leaving a broad zone of algal cells and an indistinct at the base. The —the cup-like wall surrounding the hymenium—remains thin along the sides but flares slightly above, its surface again capped by brown-tipped cells. Inside, the hymenium stains blue with iodine (I+), indicating amyloid structures, while the underlying is colourless. Slender paraphyses (sterile filaments) are mostly unbranched; their swollen, dark-brown tips form a protective canopy over the asci. Each ascus (''Catillaria''-type) contains eight colourless ascospores that are divided by a single cross-wall (septum) and are ellipsoidal to slipper-shaped; when treated with potassium hydroxide solution (K) the spore envelope () swells conspicuously, a feature lost in very old spores. Asexual propagules are produced in immersed pycnidia; these flask-shaped bodies release minute, rod-shaped conidia formed on (side-bearing) chains of cells. Chemical spot tests detect argopsin and, in some species, zeorin, and the upper surface may be pigmented dull brown (K–, non-reactive) or olive-green (K– but turning red with the organic solvent N). Although ''Halecania'' resembles '' Catillaria'' in its ascus and conidiomata structure, it is set apart by having a thalline margin on the apothecia and spores with a thick, reactive perispore; it differs from '' Lecania'' by lacking sickle-shaped conidia and by the presence of dark caps on its surface cells.

Species

, Species Fungorum (in the Catalogue of Life) accepts 24 species of ''Halecania''.
* '' Halecania ahtii'' – Russian Far East
* '' Halecania alpivaga''
* '' Halecania athallina'' – Alaska
* '' Halecania australis''
* '' Halecania bryophila''
* '' Halecania elaeiza''
* '' Halecania etayoana''
* '' Halecania fuscopannariae''
* '' Halecania giraltiae''
* '' Halecania laevis''
* '' Halecania lecanorina''
* '' Halecania lobulata''
* '' Halecania micacea''
* '' Halecania pakistanica''
* '' Halecania panamensis'' – Panama
* '' Halecania pannarica''
* '' Halecania parasitica''
* '' Halecania pepegospora''
* '' Halecania ralfsii''
* '' Halecania rhypodiza''
* '' Halecania robertcurtisii'' – eastern North America
* '' Halecania santessonii'' – Russia
* '' Halecania spodomela''
*'' Halecania subalpivaga''
* '' Halecania subsquamosa''
* '' Halecania tornensis''
* '' Halecania viridescens''

References

{{Taxonbar, from=Q10516179

Leprocaulales
Lecanoromycetes genera
Lichen genera
Taxa described in 1987