# Lepraria

Lepraria is a genus of leprose (powdery) crustose lichens that grows on its substrate like patches of granular, caked up, mealy dust grains. Members of the genus are commonly called dust lichens.$^{:305}$ The main vegetative body (thallus) is made of patches of soredia (little balls of algae wrapped in fungus). There are no known mechanisms for sexual reproduction, yet members of the genus continue to speciate. Some species can form marginal lobes and appear squamulose. Because of the morphological simplicity of the thallus and the absence of sexual structures, the composition of lichen products (i.e., secondary metabolites made by lichens) are important characters to distinguish between similar species in Lepraria.

## Taxonomy

Lepraria was circumscribed in 1803 by Swedish lichenologist Erik Acharius. Jack Laundon assigned Lepraria incana as the type species of the genus in 1992. It is in the family Stereocaulaceae.
The taxonomy of Lepraria has undergone significant changes as new research methods have become available. Historically, some species now classified as Lepraria were placed in a separate genus called Leproloma, which was thought to be distinct based on features such as whitish colouring with yellow tints, a powdery surface composed of small lobes, and specific chemical compounds called dibenzofurans. However, molecular studies in 2002 showed that most species from both genera are actually part of the same evolutionary group.
Scientists use multiple characteristics to identify and classify Lepraria species, including their physical appearance (morphology), their chemical composition, and their genetic sequences. Different populations of the same species can have varying chemical compositions, known as chemotypes. This variation has led to debate among researchers about how to properly define species boundaries within the genus. While some researchers have proposed splitting the genus into many narrowly defined species based on small genetic or chemical differences, others advocate for a more conservative approach that considers multiple lines of evidence.

## Description

Species of Lepraria are characterised by their powdery, crustose thalli, which are composed almost entirely of soredia—small, granular clusters of fungal and algal cells that allow for asexual reproduction. The thallus may appear loosely attached or more firmly integrated with the substrate, forming irregular, diffuse patches or well-defined, lobed margins. Most species exhibit shades of grey, greenish-grey, or cream, lacking the bright pigmentation seen in some other lichens.
Unlike many lichen-forming fungi, Lepraria species do not produce fruiting bodies (apothecia) or sexual spores (ascospores). Instead, their reproduction relies entirely on soredia dispersal. In some species, the soredia aggregate into larger clusters known as consoredia, which may give the thallus a rough or granular texture. Some species, particularly those in wetter or more sheltered environments, may develop a cottony or membranous appearance. The thallus can also have a hypothallus—a weft of fungal hyphae at the base—ranging in colour from white to dark brown or black.
The genus Lepraria is chemically diverse, with species producing a wide range of secondary metabolites, including depsides, depsidones, aliphatic acids, and terpenoids. These substances, detectable through thin-layer chromatography, are often the primary basis for distinguishing species. Many species grow in humid, shaded environments such as tree bark, moss-covered rocks, and soil, although some are found in more exposed, dry habitats.
Molecular phylogenetics studies have refined the circumscription of Lepraria. Several species formerly included in the genus, particularly those producing usnic acid, have been reassigned to other genera within the Lecanoromycetes, including Lecanora and Leprocaulon. This reclassification has clarified Lepraria as a lineage most closely related to the family Stereocaulaceae.

## Habitat, distribution, and ecology

Lepraria species occupy a wide range of habitats but are most commonly found in shaded, humid environments where direct rainfall is limited. Many species grow on tree bark, moss-covered rocks, or decaying wood, particularly in forests with stable humidity levels. Some taxa prefer rocky substrates, particularly siliceous or calcareous surfaces, and can colonise cracks or overhangs where they are partially sheltered. Other species thrive on soil, mosses, or plant debris, often in montane or subalpine environments.
While Lepraria is often associated with moist microhabitats, certain species tolerate or even prefer more exposed conditions, such as sunlit rock faces or dry forest floors. Some species are pioneers in disturbed habitats, rapidly colonising exposed surfaces where competition from other lichens or plants is low. In contrast, others show a preference for mature forests with stable microclimates, particularly in temperate regions.
The genus has a broad geographical distribution, occurring on every continent, including Antarctica. The highest species diversity is found in temperate zones, but representatives of Lepraria are also common in tropical and boreal forests, alpine regions, and oceanic islands. Some species exhibit narrow ecological preferences and are restricted to specific regions or substrate types, while others are cosmopolitan in their distribution.

## Species

As of January 2025, Species Fungorum (in the Catalogue of Life) accepts 85 species of Lepraria.
* Lepraria achariana Flakus & Kukwa (2007) – South America
* Lepraria alba (Roth) Ach. (1799)
* Lepraria albicans (Th.Fr.) Lendemer & B.P.Hodk. (2013)
* Lepraria alpina (B.de Lesd.) Tretiach & Baruffo (2006)
* Lepraria alternata Elix (2013) – Australia
* Lepraria arbuscula (Nyl.) Lendemer & B.P.Hodk. (2013)
* Lepraria atlantica Orange (2001)
* Lepraria aurescens Orange & Wolseley (2005) – Thailand
* Lepraria barbatica Lendemer (2010)
* Lepraria bergensis Tønsberg (2002)
* Lepraria borealis Loht. & Tønsberg (1994)
* Lepraria brasiliensis Elix, A.A.Spielm. & Øvstedal (2010)
* Lepraria brodoi Lendemer & Tønsberg (2014) – North America
* Lepraria cacuminum (A.Massal.) Kümmerl. & Leuckert (1995)
* Lepraria caesiella R.C.Harris (2005)
* Lepraria caesioalba (B.de Lesd.) J.R.Laundon (1992)
* Lepraria celata Slav.-Bay. (2006)
* Lepraria chileana Grewe, Barcenas-Peña, R.Diaz & Lumbsch (2021) – Chile
* Lepraria congesta (Nyl.) Lendemer & B.P.Hodk. (2013)
* Lepraria crassissima (Hue) Lettau (1958)
* Lepraria cryophila Lendemer (2010)
* Lepraria cryptovouauxii Kukwa, Flakus & Guzow-Krzemińska (2019)
* Lepraria cupressicola (Hue) J.R.Laundon (2008)
* Lepraria dibenzofuranica Elix (2008) – Australia
* Lepraria diffusa (J.R.Laundon) Kukwa (2002)
* Lepraria disjuncta Lendemer (2010)
* Lepraria ecorticata (J.R.Laundon) Kukwa (2006)
* Lepraria elobata Tønsberg (1992)
* Lepraria finkii (B.de Lesd.) R.C.Harris (1985)
* Lepraria friabilis Lendemer, K.Knudsen & Elix (2008)
* Lepraria gelida Tønsberg & Zhurb. (2006)
* Lepraria glaucosorediata Flakus & Kukwa (2009)
* Lepraria goughensis Elix & Øvstedal (2005)
* Lepraria gracilescens (Nyl.) Lendemer & B.P.Hodk. (2013)
* Lepraria granulata Slav.-Bay. (2007) – Eastern and Central Europe
* Lepraria granulosa Slav.-Bay. (2007)
* Lepraria harrisiana Lendemer (2012)
* Lepraria hodkinsoniana Lendemer (2011)
* Lepraria humida Slav.-Bay. & Orange (2006)
* Lepraria impossibilis Sipman (2004)
* Lepraria incana (L.) Ach. (1803)
* Lepraria indica Rajesh Bajpai & Upreti (2018) – India
* Lepraria isidiata (Llimona) Llimona & A.Crespo (2004)
* Lepraria jackii Tønsberg (1992)
* Lepraria juanfernandezii M.Kukwa (2019)
* Lepraria lanata Tønsberg (2007)
* Lepraria larrainiana Lendemer (2010) – Chile
* Lepraria lecanorica Tønsberg (2004)
* Lepraria lendemeri Bungartz, Elix, G.Hillmann & Kalb (2013)
* Lepraria leprolomopsis Diederich & Sérus. (1997)
* Lepraria leuckertiana (Zedda) L.Saag (2009)
* Lepraria lobata Elix & Kalb (2006) – Australia
* Lepraria lobificans Nyl. (1873)
* Lepraria maderensis Kukwa & Flakus (2011)
* Lepraria malouina Øvstedal (2012) – Falkland Islands
* Lepraria membranacea (Dicks.) Vain. (1921)
* Lepraria methylbarbatica Elix (2008)
* Lepraria multiacida Aptroot (2002) – Brazil
* Lepraria neojackii Flakus & Kukwa (2007) – South America
* Lepraria neozelandica Barcenas-Peña, Grewe & Lumbsch (2021) – New Zealand
* Lepraria nigrocincta Diederich, Sérus. & Aptroot (1997)
* Lepraria nivalis J.R.Laundon (1992)
* Lepraria normandinoides Lendemer & R.C.Harris (2007)
* Lepraria nothofagi Elix & Kukwa (2010)
* Lepraria nylanderiana Kümmerl. & Leuckert (1995)
* Lepraria ohmiensis Kashiw., Keis. Kobay. & K.H.Moon (2009) – Japan
* Lepraria oxybapha Lendemer (2012)
* Lepraria pacifica Lendemer (2011)
* Lepraria pallida Sipman (2004)
* Lepraria pseudoarbuscula (Asahina) Lendemer & B.P.Hodk. (2013)
* Lepraria pulchra Orange & Wolseley (2005) – Thailand
* Lepraria rigidula (B.de Lesd.) Tønsberg (1992)
* Lepraria salazinica Tønsberg (2007)
* Lepraria santosii Argüello & A.Crespo (2006)
* Lepraria sekikaica Elix (2011) – Australia
* Lepraria sipmaniana (Kümmerl. & Leuckert) Kukwa (2002)
* Lepraria squamatica Elix (2006) – Australia
* Lepraria subalbicans (I.M.Lamb) Lendemer & B.P.Hodk. (2013)
* Lepraria sulphurella Räsänen (1949)
* Lepraria svalbardensis Tønsberg (2009)
* Lepraria sylvicola Orange (2006)
* Lepraria tenella (Tuck.) Lendemer & B.P.Hodk. (2013)
* Lepraria toilenae Kantvilas & Kukwa (2006)
* Lepraria torii Pérez-Ort. & T.Sprib. (2009)
* Lepraria umbricola Tønsberg (1992)
* Lepraria ulrikii Grewe, Barcenas-Peña, R.Diaz & Lumbsch (2021) – Australasia
* Lepraria vouauxii (Hue) R.C.Harris (1987)
* Lepraria xanthonica Lendemer (2010)
* Lepraria xerophila Tønsberg (2004)
* Lepraria zeorinica (L.Saag) Kukwa (2009)