''Crocodia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

foliose lichen A foliose lichen is a lichen with flat, leaf-like , which are generally not firmly bonded to the substrate on which it grows. It is one of the three most common growth forms of lichens. It typically has distinct upper and lower surfaces, each o ...

s in the family

Peltigeraceae The Peltigeraceae are a family of lichens in the order Peltigerales. The Peltigeraceae, which contains 15 genera and about 600 species, has recently (2018) been emended to include the families Lobariaceae and Nephromataceae. Many Peltigeraceae sp ...

. It has eight species. The genus has a

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

, although most species occur in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

and

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

regions of the Southern Hemisphere. The main characteristics of the genus that separate it from its parent genus, ''

Pseudocyphellaria ''Pseudocyphellaria'' is a genus of large, leafy lichens that are sometimes referred to as "specklebelly" lichens.Brodo, I. M., S. D. Sharnoff, and S. Sharnoff. 2001. ''Lichens of North America''. Yale University Press: New Haven. The genus has ...

'', include a yellow

medulla Medulla (Latin for "marrow") or medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ...

and yellow

pseudocyphella Pseudocyphellae (singular ''pseudocyphella'') are structures in lichens that appear as tiny pores on the outer surface (the cortex) of the lichen. They are caused when there is a break in the cortex of the lichen, and the medullary hyphae extend ...

e (tiny pores for gas exchange) on the lower

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

surface.

Taxonomy

''Crocodia'' was originally proposed by German naturalist

Johann Heinrich Friedrich Link Johann Heinrich Friedrich Link (2 February 1767 – 1 January 1851) was a German natural history, naturalist and botanist. Biography Link was born at Hildesheim as a son of the minister August Heinrich Link (1738–1783), who taught him love ...

in 1833, with ''Crocodia aurata'' assigned as the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

. A 2013

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

-based analysis of the Lobariaceae showed that the large genus ''Pseudocyphellaria'' was

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

. In 2011, Jørgensen and Galloway had proposed to split ''Pseudocyphellaria'' into two genera, with the large

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

containing the type species '' P. crocata'' to retain the original genus name. The genus name ''Crocodia'' was reinstated by Moncada and colleagues for the smaller ''P. aurata''

(containing ''P. aurata'' and ''P. clathrata''). Additional species were transferred to the genus soon after.

Description

Characteristics of the genus include a foliose (leafy)

, yellow

, and yellow

e on the lower thallus surface. The form of the thallus ranges from neat rosettes to irregularly spreading. The

photobiont A lichen ( , ) is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualistic relationship.

partner is

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

(possibly from the genus ''

Dictyochloropsis ''Dictyochloropsis'' is a genus of Unicellular organism, unicellular Green algae, green alga of the phylum Chlorophyta. This genus consists of Free-swimming, free-living algae which have a reticulate (net-like) chloroplast that varies slightly in ...

''), while cyanobacteria occur in internal

cephalodia A cephalodium () is a small gall-like structure found in some lichens. They occur only in lichens which contain both cyanobacterial and green algal partners. Cephalodia can occur within the tissues of the lichen, or on its upper or lower surface. ...

. The

apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...

are pedicellate and usually pubescent or verrucose. The sexual spores (

ascospore In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...

s) are fusiform (spindle-shaped) to

ellipsoid An ellipsoid is a surface that can be obtained from a sphere by deforming it by means of directional Scaling (geometry), scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a Surface (mathemat ...

, brown, and usually have three

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

; the asexual spores (

conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

) are colourless with a bacilliform shape. Compounds called

triterpenoid Triterpenes are a class of terpenes composed of six isoprene units with the molecular formula C30H48; they may also be thought of as consisting of three terpene units. Animals, plants and fungi all produce triterpenes, including squalene, the pre ...

s are the usual

lichen product Lichen products, also known as lichen substances, are organic compounds produced by a lichen. Specifically, they are secondary metabolites. Lichen products are represented in several different chemical classes, including terpenoids, orcinol deri ...

s found in the genus; they include derivatives of fernene and lupane, which are examples of

hopane Hopane is a natural chemical compound classified as a triterpene. It forms the central core of a variety of other chemical compounds which are collectively known as hopanoids. The first compound of the hopane family to be isolated and characte ...

triterpenoids.

Species interactions

'' Capronia harrisiana'' is a

lichenicolous fungus A lichenicolous fungus is a member of a specialised group of fungi that live exclusively on lichens as their host organisms. These fungi, comprising over 2,000 known species across 280 genera, exhibit a wide range of ecological strategies, includ ...

that has been recorded growing on ''Crocodia aurata'' in southeastern North America. Other lichenicolous fungi growing on members of ''Crocodia'' include '' Homostegia pelvetii'', '' Abrothallus parmeliarum'', '' Arthonia epiphyscia'', '' A. fuscorubella'', '' A. pelveti'', '' A. stictaria'', '' Lichenoconium plectocarpoides'', '' Nectria heterospora'' and '' Scutula epiblastemica''.

Habitat and distribution

''Crocodia'' lichens are generally found in oceanic habitats that are humid and sheltered. Collectively, the genus has a

, with the greatest diversity in the Southern Hemisphere.

Species

* '' Crocodia arvidssonii'' – South America;

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

* '' Crocodia aurata'' – widespread * '' Crocodia asticta'' * '' Crocodia aurora'' * '' Crocodia fossulata'' * '' Crocodia guilleminii'' * '' Crocodia poculifera'' –

palaeotropics The Paleotropical kingdom (Paleotropis) is a floristic kingdom composed of the tropical areas of Africa, Asia and Oceania (excluding Australia and New Zealand), as proposed by Ronald Good and Armen Takhtajan. Part of its flora is inherited fro ...

* '' Crocodia punctulata''

References

{{Taxonbar, from=Q47519611 Peltigeraceae Peltigerales genera Lichen genera Taxa described in 1833 Taxa named by Johann Heinrich Friedrich Link