Rhizocarpon Caesium

''Rhizocarpon'' is a genus of crustose, saxicolous (or sometimes lichenicolous), lichens in the family Rhizocarpaceae. The genus is common in arctic-alpine environments, but also occurs throughout temperate, subtropical, and even tropical regions. They are commonly known as map lichens because of the prothallus forming border-like bands between colonies in some species, like the common map lichen (''Rhizocarpon geographicum'').

Taxonomy and phylogeny

Together with three small genera (''Catolechia'', ''Poeltinula'' and ''Epilichen''), ''Rhizocarpon'' constitutes the family Rhizocarpaceae. Historically, ca 389 names have been used. However, many species concepts are ill-defined, many names have been synonymized and new species are regularly being described, so true number of species is not entirely clear as of now, but is estimated to be around 200.

In molecular work, the genus has also been shown to be paraphyletic, with closely related genera being nested within ''Rhizocarpon''.

Common traits

With so many species in a morphologically diverse genus it is difficult to say something general about morphology and anatomy and there will inevitably be some exceptions. However, they do share some key traits. They are all crustose and mostly saxicolous (rock-living), with some being lichenicolous (lichen parasites) on other saxicolous lichens. They are all lecideoid, meaning they have apothecia without a thallus margin containing algae.

Ascus and ascospores

The genus has a distinct type of ascus, the Rhizocarpon-type, which is bitunicate with the inner ascus-wall being slightly apically thickened. Ascospores are considered important characters for determining species within the genus. They are either 2-celled (1-septate) or multi-celled (muriform) and are either hyaline or pigmented (green or brown), often with a characteristic halo () visible when viewed in a microscope. Asci contain eight, two or rarely one spore.

Species

, Species Fungorum (in the Catalogue of Life) accepts 75 species of ''Rhizopogon''.

*''Rhizocarpon advenulum''
*''Rhizocarpon alpicola''
*''Rhizocarpon amphibium''
*''Rhizocarpon anaperum''
*''Rhizocarpon austroalpinum'' – Australia
*''Rhizocarpon austroamphibium'' – Australia
*''Rhizocarpon badioatrum''
*'' Rhizocarpon bicolor'' – Australia
*'' Rhizocarpon caeruleoalbum''
*'' Rhizocarpon caesium'' – Europe
*'' Rhizocarpon chioneum''
*'' Rhizocarpon cinereonigrum''
*'' Rhizocarpon cinereovirens''
*'' Rhizocarpon clausum''
*'' Rhizocarpon cleptophilum'' – Greenland
*'' Rhizocarpon copelandii''
*''Rhizocarpon dahlii''
*'' Rhizocarpon dimelaenae''
*'' Rhizocarpon diploschistinum''
*'' Rhizocarpon disporum''
*''Rhizocarpon distinctum''
*'' Rhizocarpon eupetraeoides''
*'' Rhizocarpon exiguum'' – Australia
*'' Rhizocarpon expallescens''
*'' Rhizocarpon ferax''
*'' Rhizocarpon flavomedullosum'' – Australia
*'' Rhizocarpon furfurosum''
*'' Rhizocarpon geminatum''
*''Rhizocarpon geographicum''
*''Rhizocarpon grande''
*'' Rhizocarpon haidense''
*'' Rhizocarpon hochstetteri''
*''Rhizocarpon inarense''
*'' Rhizocarpon infernulum''
*'' Rhizocarpon intermediellum''
*'' Rhizocarpon jemtlandicum''
*'' Rhizocarpon johnstonii''
*'' Rhizocarpon kerguelense''
*'' Rhizocarpon lavatum''
*'' Rhizocarpon lecanorinum''
*'' Rhizocarpon lusitanicum''
*'' Rhizocarpon macrosporum''
*''Rhizocarpon malvinae'' – Falkland Islands
*'' Rhizocarpon mawsonii''
*'' Rhizocarpon ochrolechiae''
*'' Rhizocarpon oederi''
*'' Rhizocarpon oxydatum'' – New Zealand
*'' Rhizocarpon ozsoyae'' – Antarctica
*'' Rhizocarpon pallidum''
*'' Rhizocarpon petraeum''
*'' Rhizocarpon polycarpum''
*'' Rhizocarpon postumum''
*'' Rhizocarpon purpurascens'' – New Zealand
*'' Rhizocarpon pusillum''
*'' Rhizocarpon quinonum'' – Alaska
*'' Rhizocarpon reductum''
*'' Rhizocarpon richardii''
*'' Rhizocarpon ridescens''
*'' Rhizocarpon roridulum''
*'' Rhizocarpon saurinum''
*'' Rhizocarpon simillimum''
*''Rhizocarpon sipmanianum''
*'' Rhizocarpon smaragdulum'' – Siberia
*'' Rhizocarpon subareolatum'' – Greenland
*'' Rhizocarpon subgeminatum''
*'' Rhizocarpon sublavatum'' – Europe
*'' Rhizocarpon submodestum''
*'' Rhizocarpon subpostumum''
*'' Rhizocarpon sulphurosum''
*'' Rhizocarpon sunchonense'' – South Korea
*'' Rhizocarpon superficiale''
*'' Rhizocarpon tephromelae''
*'' Rhizocarpon timdalii'' – Europe; North America
*'' Rhizocarpon tinei''
*'' Rhizocarpon torquatum'' /
*''Rhizocarpon transiens''
*''Rhizocarpon tungurahuae''
*'' Rhizocarpon umbilicatum''
*'' Rhizocarpon umense''
*'' Rhizocarpon vigilans'' – Australia
*'' Rhizocarpon viridiatrum''
*''Rhizocarpon vulcani'' – Japan

Gallery

File:Rhizocarpon.jpg, ''Rhizocarpon'' sp. on a mountain Zlatibor, Serbia
File:Rhizocarpon pycnocarpoides (10.3897-mycokeys.11.6670) Figure 10.jpg, ''Rhizocarpon pycnocarpoides''

References

{{Taxonbar, from=Q3018582

Rhizocarpaceae
Lichen genera
Lecanoromycetes genera
Taxa named by Augustin Pyramus de Candolle
Taxa described in 1805