Dendrographa Franciscana
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''Dendrographa'' 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 ...
of
lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
-forming
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
in the family
Roccellaceae The Roccellaceae are a family (biology), family of mostly lichen-forming fungi in the order Arthoniales, established by the French botanist François Fulgis Chevallier in 1826. Species in the family exhibit various lichen growth forms, growth ...
. It has seven species. These lichens form small, shrubby tufts that cling to bark or coastal rocks along the Pacific seaboard, with brown-grey main branches and paler, pencil-thin tips that lack a protective outer skin. The genus was originally established in 1895 for a single Pacific coast species, but
molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...
studies in the 2010s expanded it by transferring four additional species from other genera and led to the discovery of a seventh species in Brazil.


Taxonomy

The genus ''Dendrographa'' was
circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...
by the British lichenologist Otto Vernon Darbishire in 1895 to accommodate the distinctive Pacific-coast lichen then known as ''Roccella leucophaea''; Darbishire recognised that its
fruticose A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy lichen growth forms, growth structure. It is formed from a symbiotic relationship of a photobiont such as green algae or less commonly cyanobacteri ...
habit, branch tips and
calcium oxalate Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula or . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydr ...
-encrusted
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 ...
set it apart from ''
Roccella Roccella may refer to: * Roccella Valdemone, a municipality in Sicily, Italy * Roccella Ionica (or Roccella Jonica), a municipality in Calabria, Italy * The lichen genus '' Roccella'', known for the species ''Roccella tinctoria ''Roccella tinct ...
'' and related genera. He therefore transferred the species as ''Dendrographa leucophaea'' and designated it 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 ...
of his new genus. For more than a century ''Dendrographa'' was treated as
monospecific In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...
until Sundin and Tehler's 1996
monograph A monograph is generally a long-form work on one (usually scholarly) subject, or one aspect of a subject, typically created by a single author or artist (or, sometimes, by two or more authors). Traditionally it is in written form and published a ...
combined detailed
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
with
thin-layer chromatography Thin-layer chromatography (TLC) is a chromatography technique that separates components in non-volatile mixtures. It is performed on a TLC plate made up of a non-reactive solid coated with a thin layer of adsorbent material. This is called the sta ...
to define the genus more precisely and to describe a second species, ''D. alectoroides''. Their study also documented two informal forms produced by vegetative fragmentation, emphasising that the genus was characterised by the absence of specialised propagules (
isidia An isidium (plural: isidia) is a tiny, wart- or finger-like outgrowth on the thallus surface of certain lichen species. It is one of two principal types of vegetative reproduction, vegetative reproductive structures in lichens, the other being ...
or
soredia Soredia are common reproduction, reproductive structures of lichens. Lichens asexual reproduction, reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungus, fung ...
) and by
protocetraric acid Protocetraric acid is a chemical compound with the molecular formula . It is a secondary metabolite produced by a variety of lichens and is classified as a depsidone. History In 1845 Knop and Schnedermann isolated crystalline cetraric acid fro ...
chemistry.
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 ...
work in the early 2010s reshaped the genus. A broad rDNA/RPB2 analysis of the
Arthoniales The Arthoniales is the second largest order of mainly crustose lichens, but fruticose lichens are present as well. The order contains around 1500 species, while the largest order with lichenized fungi, the Lecanorales, contains more than 14000 s ...
by Ertz and Tehler showed that four sorediate species previously scattered in ''
Roccellina ''Roccellina'' is a genus of lichen-forming fungi in the family Roccellaceae. Taxonomy The genus was circumscribed in 1898 by British botanist Otto Vernon Darbishire with '' Roccellina condensata'' as the type. At that time, only species. A yea ...
'', ''
Dirina ''Dirina'' is a genus of lichen-forming fungi in the family Roccellaceae. All ''Dirina'' species are crustose lichens with a whitish to greyish brown thallus, and live either on rock or on bark–some species can live on both. The partner is ...
'' and allied genera actually nested within the ''Dendrographa''
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 ...
; they were therefore transferred as ''D. conformis'', ''D. decolorans'', ''D. franciscana'' and ''D. latebrarum'' in 2011. The decade closed with the description of ''D. austrosorediata'' from wave-washed granite in southern Brazil—the first member of the genus recorded outside the north-eastern Pacific—which expanded the genus to seven accepted species.


Description

''Dendrographa'' lichens form small, shrubby (
fruticose A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy lichen growth forms, growth structure. It is formed from a symbiotic relationship of a photobiont such as green algae or less commonly cyanobacteri ...
) tufts that cling to bark or coastal rock along the Pacific seaboard of
Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...
and
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
. The main branches are brown-grey and often flattened near the base, but the younger, pencil-thin tips—and the many side that burst through the surface—lack a protective skin () and appear paler, with a fine white, powdery bloom (). Branches sometimes fuse to one another, and broken tips readily re-establish elsewhere, helping the lichen spread. A tightly packed outer of parallel fungal threads (
hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...
e) encloses a looser inner
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 ...
; some specimens accumulate tiny
calcium oxalate Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula or . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydr ...
crystals. The genus does not produce dedicated vegetative
propagule In biology, a propagule is any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by organisms ...
s such as
soredia Soredia are common reproduction, reproductive structures of lichens. Lichens asexual reproduction, reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungus, fung ...
or
isidia An isidium (plural: isidia) is a tiny, wart- or finger-like outgrowth on the thallus surface of certain lichen species. It is one of two principal types of vegetative reproduction, vegetative reproductive structures in lichens, the other being ...
, so reproduction relies chiefly on sexual fruit bodies (
ascomata An ascocarp, or ascoma (: ascomata), is the fruiting body (sporocarp (fungi), sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded ascus, asci, each of which typically contains four to ...
) and accidental fragmentation. Ascomata are small lateral , 0.3–3 mm across, that erupt through the cortex and eventually sit on a narrow base; their exposed surface is smooth, white and often slightly domed, ringed by a pale margin of cracked cortex. Each
ascus An ascus (; : asci) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some gen ...
contains eight colourless, three-segmented (3-septate) spindle-shaped
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, roughly 22–24 μm long by 6–8 μm wide, which are shot into the air when mature. Tiny black
pycnidia A pycnidium (plural pycnidia) is an asexual fruiting body produced by mitosporic fungi, for instance in the order Sphaeropsidales ( Deuteromycota, Coelomycetes) or order Pleosporales (Ascomycota, Dothideomycetes). It is often spherical or inve ...
—flask-shaped cavities sunken in the thallus—exude curved
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 ...
about 11–15 μm long. The
photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...
partner is the orange-tinged green alga '' Trentepohlia'', whose cells (10–20 μm) are scattered throughout the interior. All examined specimens contain
protocetraric acid Protocetraric acid is a chemical compound with the molecular formula . It is a secondary metabolite produced by a variety of lichens and is classified as a depsidone. History In 1845 Knop and Schnedermann isolated crystalline cetraric acid fro ...
as their principal
secondary metabolite Secondary metabolites, also called ''specialised metabolites'', ''secondary products'', or ''natural products'', are organic compounds produced by any lifeform, e.g. bacteria, archaea, fungi, animals, or plants, which are not directly involved ...
, sometimes accompanied by trace amounts of fumarprotocetraric and succinprotocetraric acids; these closely related compounds are thought to deter grazers and mitigate
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
stress.


Species

*'' Dendrographa alectoroides'' *'' Dendrographa austrosorediata'' – Brazil *'' Dendrographa conformis'' *'' Dendrographa decolorans'' *'' Dendrographa franciscana'' *'' Dendrographa latebrarum'' *'' Dendrographa leucophaea''


References

{{Taxonbar, from=Q5256754 Roccellaceae Arthoniomycetes genera Lichen genera Taxa named by Otto Vernon Darbishire Taxa described in 1895