Parmeliaceae
Encyclopedia
The Parmeliaceae is a large and diverse
family of Lecanoromycetes
. With over 2000 species
in roughly 87 genera
, it is currently regarded as the largest family of lichen
forming fungi. The most speciose genera in the family are the well known groups: Xanthoparmelia
(800+ species), Usnea
(500+ species), Parmotrema
(350+ species), and Hypotrachyna
(190+ species).
Nearly all members of the family have a symbiotic association with a green alga
(most often Trebouxia
spp., but Asterochloris spp. are known to associate with some species). The majority of Parmeliaceae species have a foliose, fruticose, or subfruticose growth form. The morphological
diversity and complexity exhibited by this group is enormous, and many specimens are exceedingly difficult to identify down to the species level.
The family has a cosmopolitan distribution
, and can be found in a wide range of habitat
s and climatic regions
. This includes everywhere from roadside pavement to alpine rocks, from tropical rainforest trees to subshrubs in the arctic tundra. Members of the Parmeliaceae can be found in most terrestrial
environments.
. However, despite the family being one of the most thoroughly studied groups of lichens, several relationships within the family still remain unclear. Phylogenetic analysis tentatively supports the existence of six separate clades
in the family:
However, this still leaves roughly 42 Parmeliaceae genera unplaced.
, is even a lichenicolous fungus. They can be a variety of colours, from whitish to grey, green to yellow, or brown to blackish (or any combination therein). Many genera are lobe forming, and nearly all are heteromerous (which are corticate on both sides). Species are usually rhizinate on the lower surface, occasionally with holdfasts, rhizohyphae, or a hypothallus. Only a few genera have a naked lower surface (for example Usnea
, Hypogymnia
and Menegazzia
). The upper surface has a pored or non-pored epicortex. Medulla
is solid, but often loosely woven.
species have 2-spores per ascus.
s are simple, hyaline
, and often small. Conidia
generally arise laterally from the joints of conidiogenous hyphae (Parmelia
-type), but arise terminally from these joints in a small number of species (Psora
-type). The conidia can have a broad range of shapes: cylindrical to bacilliform, bifusiform, fusiform, sublageniform, unciform, filiform, or curved. Pycnidia
are immersed or rarely emergent from the upper cortex, are produced along the lamina or margins, pyriform in shape, and dark-brown to black in colour.
-type, Cetraria
-type, intermediate-type), isolichenan and/or other polysaccharide
s being known from the cell wall
s of many species.
. In particular the species Trebouxia jamesii appears to be especially prominent. Some Parmeliaceae genera are also known to associate with Asterochloris, but the frequence of this association is not yet known. In general photobiont diversity within the Parmeliaceae is a little studied subject, and much is left to discover here.
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family of Lecanoromycetes
Lecanoromycetes
Lecanoromycetes is the largest class of lichenized fungi. It belongs to the subphylum Pezizomycotina in the phylum Ascomycota. The asci of the Lecanoromycetes most often release spores by rostrate dehiscence....
. With over 2000 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in roughly 87 genera
Genera
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, it is currently regarded as the largest family of lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
forming fungi. The most speciose genera in the family are the well known groups: Xanthoparmelia
Xanthoparmelia
Xanthoparmelia is a genus of lichen belonging to the family Parmeliaceae. Xanthoparmelia is synonymous with Almbornia, Neofuscelia, Chondropsis, Namakwa, Paraparmelia, and Xanthomaculina.This family of lichen is commonly found on the mid-east coast of the United States.The name means 'golden...
(800+ species), Usnea
Usnea
Usnea is the generic and scientific name for several species of lichen in the family Parmeliaceae, that generally grow hanging from tree branches, resembling grey or greenish hair. It is sometimes referred to commonly as Old Man's Beard, Beard Lichen, or Treemoss...
(500+ species), Parmotrema
Parmotrema
Parmotrema is a genus of lichen belonging to the family Parmeliaceae.-External links:*...
(350+ species), and Hypotrachyna
Hypotrachyna
Hypotrachyna is a genus of lichenized fungi within the Parmeliaceae family. According to the Dictionary of the Fungi , the widespread genus contains about 198 species...
(190+ species).
Nearly all members of the family have a symbiotic association with a green alga
Green algae
The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...
(most often Trebouxia
Trebouxia
In taxonomy, Trebouxia is a genus of algae, specifically of the Microthamniales.-Scientific databases:* * *...
spp., but Asterochloris spp. are known to associate with some species). The majority of Parmeliaceae species have a foliose, fruticose, or subfruticose growth form. The morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
diversity and complexity exhibited by this group is enormous, and many specimens are exceedingly difficult to identify down to the species level.
The family has a cosmopolitan distribution
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
, and can be found in a wide range of habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s and climatic regions
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
. This includes everywhere from roadside pavement to alpine rocks, from tropical rainforest trees to subshrubs in the arctic tundra. Members of the Parmeliaceae can be found in most terrestrial
Terrestrial plant
A terrestrial plant is one that grows on land. Other types of plants are aquatic , epiphytic , lithophytes and aerial ....
environments.
Taxonomy
Based on several molecular phylogenetic studies, the Parmeliaceae as currently circumscribed has been shown to be a monophyletic group. This circumscription is inclusive of the previously described families Alectoriaceae, Anziaceae, Hypogymniaceae, and Usneaceae, which are all no longer recognised by most lichen systematistsSystematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
. However, despite the family being one of the most thoroughly studied groups of lichens, several relationships within the family still remain unclear. Phylogenetic analysis tentatively supports the existence of six separate clades
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
in the family:
- Alectorioid clade (3 genera)
- Cetrarioid clade (8 genera)
- Hypogymnioid clade (4 genera)
- Letharioid clade (2 genera)
- Parmelioid clade (26 genera)
- Psiloparmelioid clade (2 genera)
However, this still leaves roughly 42 Parmeliaceae genera unplaced.
Thallus
Parmeliaceae thalli are most often foliose, fruticose or subfruticose, but can be umblicate, peltate, caespitose, crustose, or subcrustose. One genus, NesolechiaNesolechia (fungus)
Nesolechia is a genus of fungi that grows on lichens. It probably evolved from a lichen ancestor, as it is closely related to many lichenized species of fungi.-External links:* at Index Fungorum...
, is even a lichenicolous fungus. They can be a variety of colours, from whitish to grey, green to yellow, or brown to blackish (or any combination therein). Many genera are lobe forming, and nearly all are heteromerous (which are corticate on both sides). Species are usually rhizinate on the lower surface, occasionally with holdfasts, rhizohyphae, or a hypothallus. Only a few genera have a naked lower surface (for example Usnea
Usnea
Usnea is the generic and scientific name for several species of lichen in the family Parmeliaceae, that generally grow hanging from tree branches, resembling grey or greenish hair. It is sometimes referred to commonly as Old Man's Beard, Beard Lichen, or Treemoss...
, Hypogymnia
Hypogymnia
Hypogymnia is a genus of lichenized fungi within the Parmeliaceae family....
and Menegazzia
Menegazzia
Menegazzia is a genus of lichenized fungi containing roughly 70 currently accepted species. The group is sometimes referred to as the tree flutes, honeycombed lichens, or hole-punch lichens. The most obvious morphological feature of the genus is the distinctive perforations spread across the upper...
). The upper surface has a pored or non-pored epicortex. Medulla
Medulla
Medulla refers to the middle of something and derives from the Latin word for marrow. Its anatomical uses include:* Medulla oblongata, a part of the brain stem* Renal medulla, a part of the kidney* Adrenal medulla, a part of the adrenal gland...
is solid, but often loosely woven.
Apothecia
Apothecia are lecanorine, produced along the lamina or margin, and sessile to pedicellate (or less often sunken). Thalline exciple is concolourous with the thallus. Asci are amyloid, and the vast majority of species have 8-spores per ascus, though a few species are many-spored, and several MenegazziaMenegazzia
Menegazzia is a genus of lichenized fungi containing roughly 70 currently accepted species. The group is sometimes referred to as the tree flutes, honeycombed lichens, or hole-punch lichens. The most obvious morphological feature of the genus is the distinctive perforations spread across the upper...
species have 2-spores per ascus.
Spores
AscosporeAscospore
An ascospore is a spore contained in an ascus or that was produced inside an ascus. This kind of spore is specific to fungi classified as ascomycetes ....
s are simple, hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
, and often small. Conidia
Conidium
Conidia, sometimes termed conidiospores, are asexual, non-motile spores of a fungus and are named after the greek word for dust, konia. They are also called mitospores due to the way they are generated through the cellular process of mitosis...
generally arise laterally from the joints of conidiogenous hyphae (Parmelia
Parmelia
Parmelia may refer to:* Parmelia , the barque in which were transported the first settlers of the British colony of Western Australia in 1829* Parmelia , a large genus of lichens with global distribution...
-type), but arise terminally from these joints in a small number of species (Psora
Psora
Psora is a genus of fungi within the Psoraceae family.-External links:* at Index Fungorum...
-type). The conidia can have a broad range of shapes: cylindrical to bacilliform, bifusiform, fusiform, sublageniform, unciform, filiform, or curved. Pycnidia
Pycnidium
A pycnidium is an asexual fruiting body produced by mitosporic fungi in the form order Sphaeropsidales . It is often spherical or inversely pearshaped and its internal cavity is lined with conidiophores. When ripe, an opening generally appears at the top, through which the pycnidiospores escape....
are immersed or rarely emergent from the upper cortex, are produced along the lamina or margins, pyriform in shape, and dark-brown to black in colour.
Chemistry
Members of the Parmeliaceae exhibit a diverse chemistry, with several types of lichenan (XanthoparmeliaXanthoparmelia
Xanthoparmelia is a genus of lichen belonging to the family Parmeliaceae. Xanthoparmelia is synonymous with Almbornia, Neofuscelia, Chondropsis, Namakwa, Paraparmelia, and Xanthomaculina.This family of lichen is commonly found on the mid-east coast of the United States.The name means 'golden...
-type, Cetraria
Cetraria
Cetraria is a genus of fruticose lichens that associate with green algae as photobionts. Most species are found at high latitudes, occurring on sand or heath...
-type, intermediate-type), isolichenan and/or other polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
s being known from the cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
s of many species.
Photobiont
The main photobiont genus that associates with Parmeliaceae species is the Chlorophyte TrebouxiaTrebouxia
In taxonomy, Trebouxia is a genus of algae, specifically of the Microthamniales.-Scientific databases:* * *...
. In particular the species Trebouxia jamesii appears to be especially prominent. Some Parmeliaceae genera are also known to associate with Asterochloris, but the frequence of this association is not yet known. In general photobiont diversity within the Parmeliaceae is a little studied subject, and much is left to discover here.
Notable taxa
Some well known members of the Parmeliaceae are:- the genus ParmeliaParmelia (lichen)Parmelia is a large genus of lichenized fungus with a global distribution, extending from the Arctic to the Antarctic continent but concentrated in temperate regions. 125 species have been recorded on the Indian sub-continent...
- the genus UsneaUsneaUsnea is the generic and scientific name for several species of lichen in the family Parmeliaceae, that generally grow hanging from tree branches, resembling grey or greenish hair. It is sometimes referred to commonly as Old Man's Beard, Beard Lichen, or Treemoss...
(old man's beard) - OakmossOakmossEvernia prunastri, also known as Oakmoss, is a species of lichen. It can be found in many mountainous temperate forests throughout the Northern Hemisphere, including parts of France, Portugal, Spain, North America, and much of Central Europe...
(Evernia prunastri) - Iceland mossIceland mossIceland moss is a lichen whose erect or ascending foliaceous habit gives it something of the appearance of a moss, whence probably the name...
(Cetraria islandica) - Wila (Bryoria fremontii)
External links
- Index Fungorum
- Parmeliaceae at the online Encyclopedia of Life
- Parmeliaceae on Wikispecies.