{{Short description|Genus of lichens}} {{Automatic taxobox | image = Nephroma arcticum (29071953967).jpg | image_caption = ''Nephroma arcticum'' | taxon = Nephroma | authority = [[Erik Acharius|Ach.]] (1809) | type_species = ''[[Nephroma arcticum]]'' | type_species_authority = ([[Carl Linnaeus|L.]]) [[Torss.]] (1843) | subdivision_ranks = Species | subdivision = See text | synonyms_ref = <ref name="Species Fungorum synonymy"/> | synonyms = *''Dermatodea'' {{au|[[Vent.]] (1799)}} *''Peltidea subdiv. Opisteria'' {{au|Ach. (1803)}} *''Opisteria'' {{au|(Ach.) [[Vain.]] (1909)}} *''Nephromatomyces'' {{au|[[E.A.Thomas]] (1939)}} *''Nephromiomyces'' {{au|E.A.Thomas ex [[Cif.]] & [[Tomas.]] (1953)}} *''Ornatinephroma'' {{au|[[Gyeln.]] (1934)}} }}

'''''Nephroma''''' is a [[genus]] of medium to large foliose [[lichen]]s. The genus has a widespread distribution.<ref name=Kirk2008>{{cite book |vauthors=Kirk PM, Cannon PF, Minter DW, Stalpers JA |title=Dictionary of the Fungi. |edition=10th |publisher=CABI |location=Wallingford |year=2008|page=467|isbn=978-0-85199-826-8}}</ref> They are sometimes called kidney lichens, named after the characteristic kidney-shaped [[apothecia]] that they produce on the lower surface of their lobe tips, which often curl upwards and thus are visible from above.<ref name="Brodo2001">{{cite book |vauthors=Sharnoff S, Brodo IM, Sharnoff SD|title=Lichens of North America |publisher=Yale University Press |location=New Haven, Connecticut |year=2001 |isbn=978-0-300-08249-4}}</ref> Sterile specimens that do not have apothecia can look somewhat like ''[[Melanelia]]'', ''[[Peltigera]]'', ''[[Platismatia]]'', or ''[[Asahinea]]''. Most species grow either on mossy ground or rocks, or on trees.<ref name="Brodo2001"/>

All species of ''Nephroma'' contain [[cyanobacteria]] (in the genus ''[[Nostoc]]'') as a [[photobiont]], which allows the organism to [[nitrogen fixation|fix nitrogen]]. In some species the cyanobacteria is the sole photobiont, while other species also contain a [[green alga]] photobiont (''[[Coccomyxa]]'') and the cyanobacteria is restricted to warty [[cephalodia]] on the upper or lower surface of the lichen.<ref name="Brodo2001"/>

==Description==

Species of ''Nephroma'' have a stratified foliose [[thallus]] with a {{lichengloss|cortex}} that is well-developed on both the upper and lower surfaces. The fruit bodies ([[apothecia]]) are formed on the lower surface of the thallus, which is later curved backward to expose the [[hymenium]] (spore-bearing surface). Initially, the ascomata are immersed with a vegetative covering that splits open at later stages of development. In contrast to all other groups of [[Peltigerales]], the [[ascus|asci]] of ''Nephroma'' have neither a gelatinous coat nor an [[iodine]]-positive apical ring. The brown [[ascospore]]s are elongated, and have a crosswise partition ([[septum|septa]]). Reproductive structures called [[soredia]], [[isidia]], or {{lichengloss|lobules}} are present in most species.<ref name="Lohtander 2002"/>

The lower surface shows important diagnostic features that vary between species. Some species have a thin layer of very short hairs called pseudotomentum, while others have a distinct mat of longer hairs called tomentum. In species like ''N.&nbsp;resupinatum'', scattered white papillae are visible on the lower surface. These features, along with the presence and nature of reproductive structures (soredia, isidia), are key characteristics for species identification.<ref name="Westberg & Ekman 2024"/>

==Chemistry==

Species of ''Nephroma'' can contain various [[triterpenoid]] compounds that are taxonomically significant and helpful for species identification. Chemical analysis through [[thin-layer chromatography]] is sometimes necessary to distinguish between morphologically similar species.<ref name="Westberg & Ekman 2024"/>

The presence and combinations of specific triterpenoids can be diagnostic. For example, ''N. orvoi'' contains triterpenoids T1, T3, T4, and T6, while the similar-looking ''N.&nbsp;parile'' contains T2, T3, and T5. Similarly, ''N.&nbsp;tangeriense'' contains both [[zeorin]] (also known as T3) and [[dolichorrhizin]] (T6), while ''N.&nbsp;laevigatum'' in the Nordic region contains only dolichorrhizin.<ref name="Westberg & Ekman 2024"/>

Some species can only be reliably distinguished through chemical analysis. For instance, ''N.&nbsp;helveticum'' and ''N.&nbsp;tropicum'' are morphologically identical but can be differentiated by their triterpenoid content, with ''N.&nbsp;helveticum'' containing compounds U1 and U2, while ''N.&nbsp;tropicum'' contains U1 and U3. ''N.&nbsp;resupinatum'' is notable for lacking [[secondary metabolite]]s entirely, which helps distinguish it from similar species.<ref name="Westberg & Ekman 2024"/>

==Photobionts==

''Nephroma'' species form symbiotic relationships with [[photosynthesis|photosynthetic]] partners ({{lichengloss|photobionts}}) that are essential to their survival. All ''Nephroma'' species contain [[cyanobacteria]] from the genus ''[[Nostoc]]'', which not only provide products of photosynthesis but also [[nitrogen fixation|fix nitrogen]] from the atmosphere, making it available to the lichen. Some species, known as {{lichengloss|tripartite lichens}}, also contain a [[green alga]]l partner from the genus ''[[Coccomyxa]]'', while others ({{lichengloss|bipartite lichens}}) contain only ''Nostoc''.<ref name="Lohtander et al. 2003"/>

Research has shown that the ''Nostoc'' partners in ''Nephroma'' fall into two distinct genetic groups that correlate with the lichen's lifestyle. One group is found exclusively in bipartite species that typically grow on tree bark or rocks, while the other group occurs in tripartite species that usually grow on soil or among mosses. This pattern holds true across wide geographic areas – specimens of the same ''Nephroma'' species collected from different continents often contain nearly identical ''Nostoc'' strains. The green algal partners (''Coccomyxa'') in tripartite species show remarkably little genetic variation across different ''Nephroma'' species and geographic regions. These algae are closely related to some free-living species, including certain algae that live within the cells of ''[[Ginkgo biloba]]'' trees.<ref name="Lohtander et al. 2003"/>

Evolutionary studies have revealed that transitions between bipartite and tripartite forms in ''Nephroma''{{'}}s evolutionary history were complex events. When a species gained or lost the ability to partner with green algae, it also had to change the type of ''Nostoc'' it associated with, suggesting that these transitions required concurrent changes in both photobiont partnerships.<ref name="Lohtander et al. 2003"/>

==Species== [[File:Nephroma2.jpg|thumb|right|''Nephroma australe'' growing on Isla Navarino, Chile]] *''[[Nephroma arcticum]]'' {{small|(L.) Torss. (1843)}} *''[[Nephroma australe]]'' {{small|A.Rich. (1832)}} *''[[Nephroma bellum]]'' {{small|(Spreng.) Tuck. (1841)}} *''[[Nephroma cellulosum]]'' {{small|(Ach.) Ach. (1810)}} *''[[Nephroma expallidum]]'' {{small|(Nyl.) Nyl. (1865)}} *''[[Nephroma flavorhizinatum]]'' {{small|Q.Tian & H.Y.Wang (2011)}}<ref name="Tian et al. 2011"/> *''[[Nephroma helveticum]]'' {{small|Ach. (1810)}} *''[[Nephroma isidiosum]]'' {{small|(Nyl.) Gyeln. (1931)}} *''[[Nephroma laevigatum]]'' {{small|Ach. (1814)}} *''[[Nephroma orvoi]]'' {{small|Timdal, M.Westb., Haugan, Hofton, Holien, Speed, Tønsberg & Bendiksby (2020)}}<ref name="Timdal et al. 2020"/> *''[[Nephroma parile]]'' {{small|(Ach.) Ach. (1810)}} *''[[Nephroma resupinatum]]'' {{small|(L.) Ach. (1810)}} *''[[Nephroma rufum]]'' {{small|(C.Bab.) P.James (1983)}} *''[[Nephroma subhelveticum]]'' {{small|H.Y.Wang (2013)}}<ref name="Wang 2013"/> *''[[Nephroma tangeriense]]'' {{small|(Maheu & A.Gillet) Gattefossé & Werner (1931)}} *''[[Nephroma tropicum]]'' {{small|(Müll.Arg.) Zahlbr. (1925)}}

==Evolution and biogeography== [[File:Pimpled Paw Lichen (5130537235).jpg|thumb|right|upright=1|''Nephroma resupinatum'' in [[Wells Gray Provincial Park]], [[British Columbia]]]] A 2011 phylogenetic study of ''Nephroma'' species in [[Macaronesia]] (the [[Azores]], [[Madeira]], and [[Canary Islands]]) revealed evidence of recent [[evolutionary radiation]] and [[neoendemism]] in the region. The study found that all five Macaronesian [[endemic]] species evolved relatively recently (within the last 19 million years) after the formation of the volcanic islands, rather than being ancient relict species. These endemic species belong to two distinct [[lineage (evolution)|lineages]], each associated with a widespread [[Holarctic]] species (''N.&nbsp;parile'' or ''N.&nbsp;laevigatum''). The research suggested that Macaronesia may have served as a source for subsequent colonisation of continental areas, with evidence of recent dispersal events from the islands to Western North America and the [[Mediterranean Basin]]. This represents the first documented case of neo-endemism in lichenised fungi from Macaronesia.<ref name="Sérusiaux et al. 2011"/>

Broader evolutionary studies have revealed complex patterns in how ''Nephroma'' species develop and maintain their symbiotic partnerships. While the fungal partners ({{lichengloss|mycobionts}}) of tripartite species do not form a single evolutionary group, their photosynthetic partners show strict patterns of association. This suggests that the evolution of different symbiotic forms in ''Nephroma'' was not a simple matter of gaining or losing a green algal partner. Instead, any shift between bipartite and tripartite forms required simultaneous changes in both the green algal and cyanobacterial partnerships.<ref name="Lohtander et al. 2003"/>

The genus also shows distinct ecological patterns in its evolution. Species that grow on trees or rocks (epiphytic or lithophytic species) consistently associate with one genetic group of ''Nostoc'' partners, while soil-dwelling species partner with a different group. This pattern holds true across continents, suggesting that these specific partnerships evolved early in the genus's history and have remained stable over long periods. Despite this specialisation in symbiotic partners, the fungal components of ''Nephroma'' species can show considerable genetic variation within species, particularly in temperate regions.<ref name="Lohtander et al. 2003"/>

==Uses==

Several species of ''Nephroma'' are restricted to pristine, [[old-growth forest]]s, and thus are important [[indicator species]] that have already influenced some forest management decisions.<ref name="Brodo2001"/> ''Nephroma occultum'' is listed as vulnerable in Canada by [[Committee on the Status of Endangered Wildlife in Canada|COSEWIC]].

One species of ''Nephroma'' has been found to produce a brown dye,<ref name = "Brough1984">{{cite journal |author=Brough SG. |year=1984 |title=Dye characteristics of British Columbia forest lichens |journal=Syesis |volume=17|pages=81–94}}</ref> while another is recorded as being used in Scotland to produce a blue dye for wool.<ref name="Uphof1959">{{cite book |author=[[Johannes Cornelius Theodorus Uphof|Uphof JCT]].|title=Dictionary of Economic Plants |publisher=Hafner Publishing Co. |location=New York |year=1959 }}</ref> ''Nephroma arcticum'' is called ''kusskoak'' by the [[Yup'ik]] of Alaska, and it is traditionally eaten after being boiled with crushed fish eggs. A medicinal tea is also made from the lichen, and is reputed to be a powerful medicine to return strength to a person who is in a weak condition.<ref name="Oswalt1957">{{cite journal |author=Oswalt WH. |year=1957 |title=A western Eskimo ethnobotany |journal=Anthropological Papers of the University of Alaska |volume=6 |issue=1 |pages=16–36}}</ref> ''N.&nbsp;arcticum'' contains several [[antifreeze protein]]s that have been [[patent]]ed by the Dutch [[multinational corporation]] [[Unilever]] for their ability to modify the growth of [[ice crystals]]; these proteins have been used to improve the texture of low-fat ice cream.<ref name="Oksanen 2006"/>

==References== {{Reflist|colwidth=30em|refs=

<ref name="Lohtander 2002">{{cite journal |last1=Lohtander |first1=K. |last2=Oksanen |first2=I. |last3=Rikkinen |first3=J. |year=2002 |title=A phylogenetic study of ''Nephroma'' |journal=Mycological Research |volume=106 |issue=7 |pages=777–787 |doi=10.1017/S0953756202006068}}</ref>

<ref name="Lohtander et al. 2003">{{cite journal |last1=Lohtander |first1=Katileena |last2=Oksanen |first2=Ilona |last3=Rikkinen |first3=Jouko |title=Genetic diversity of green algal and cyanobacterial photobionts in ''Nephroma'' (Peltigerales) |journal=The Lichenologist |volume=35 |issue=4 |year=2003 |doi=10.1016/S0024-2829(03)00051-3 |pages=325–339}}</ref>

<ref name="Oksanen 2006">{{cite journal |last=Oksanen |first=I. |title=Ecological and biotechnological aspects of lichens |journal=Applied Microbiology and Biotechnology |volume=73 |issue=4 |pages=723–34 |year=2006 |pmid=17082931 |doi=10.1007/s00253-006-0611-3}}</ref>

<ref name="Sérusiaux et al. 2011">{{cite journal |last1=Sérusiaux |first1=Emmanuël |last2=Villarreal A. |first2=Juan Carlos |last3=Wheeler |first3=Tim |last4=Goffinet |first4=Bernard |title=Recent origin, active speciation and dispersal for the lichen genus ''Nephroma'' (Peltigerales) in Macaronesia: Recent radiation of Nephroma in Macaronesia |journal=Journal of Biogeography |volume=38 |issue=6 |year=2011 |doi=10.1111/j.1365-2699.2010.02469.x |doi-access=free |pages=1138–1151}}</ref>

<ref name="Species Fungorum synonymy">{{cite web |title=Synonymy. Current Name: ''Nephroma'' Ach., in Luyken, Tentam. Histor. Lichen. Gen. Prim. Lin. Distrib. nov., Göttingae: 92 (1809) |url=https://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=3493 |publisher=[[Species Fungorum]] |access-date=24 December 2024}}</ref>

<ref name="Tian et al. 2011">{{cite journal |last1=Tian |first1=Q. |last2=Wang |first2=L.S. |last3=Wang |first3=H.Y. |last4=Zhao |first4=Z.T. |year=2011 |title=A new species of ''Nephroma'' (Nephromataceae) from the Tibetan Plateau |journal=Mycotaxon |volume=115 |pages=281–285}}</ref>

<ref name="Timdal et al. 2020">{{cite journal |last1=Timdal |first1=E. |last2=Westberg |first2=M. |last3=Haugan |first3=R. |last4=Hofton |first4=T.H. |last5=Holien |first5=H. |last6=Speed |first6=J.D.M. |last7=Tønsberg |first7=T. |last8=Bendiksby |first8=M. |year=2020 |title=Integrative taxonomy reveals a new species, ''Nephroma orvoi'', in the ''N. parile'' species complex (lichenized Ascomycota) |journal=Graphis Scripta |volume=32 |issue=4 |pages=70–85}}</ref>

<ref name="Wang 2013">{{cite journal |last1=Wang |first1=H.Y. |last2=Jiang |first2=D.F. |last3=Huang |first3=Y.H. |last4=Wang |first4=P.M. |last5=Li |first5=T. |year=2013 |title=Study on the phylogeny of ''Nephroma helveticum'' and allied species |journal=Mycotaxon |volume=125 |pages=263–275}}</ref>

<ref name="Westberg & Ekman 2024">{{cite journal |last1=Westberg |first1=M. |last2=Ekman |first2=S. |year=2024 |title=Bestämningsnyckel till nordiska njurlavar, ''Nephroma'' |journal=Achariana |volume=2.0.0 |pages=1–4 |url=https://www.diva-portal.org/smash/get/diva2:1922813/FULLTEXT01.pdf |language=sv}}</ref>

}}

{{Taxonbar|from=Q951564}}

[[Category:Lichen genera]] [[Category:Peltigeraceae]] [[Category:Taxa named by Erik Acharius]] [[Category:Peltigerales genera]] [[Category:Taxa described in 1810]]