| Megalaria | |
|---|---|
 | |
| Megalaria grossa | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Lecanorales |
| Family: | Ramalinaceae |
| Genus: | Megalaria Hafellner (1984) |
| Type species | |
| Megalaria grossa | |
| Synonyms [1] | |
| |
Megalaria is a genus of lichen-forming fungi in the family Ramalinaceae. [2] It contains 44 species of crustose lichens, the majority of which grow on bark.
The genus was circumscribed by Austrian lichenologist Josef Hafellner in 1984, with Megalaria grossa assigned as the type species. [3]
The genus Catillochroma has been synonymised with Megalaria by Alan Fryday and James Lendemer (2010) due to similar morphological characteristics. [4] While this synonymisation has been debated, recent molecular phylogenetics studies support a broader circumscription of Megalaria that includes Catillochroma, pending further research with expanded taxon sampling. [5]
Megalaria lichens have a crustose thallus (lichen body), which means it forms a crust-like layer that adheres closely to the substrate . The thallus lacks a distinct outer cortex , and its surface can range from smooth and continuous to granular in texture. The lichen's primary photosynthetic partner, or photobiont , is typically from the genus Dictyochloropsis , though other single-celled algae may also be involved. [6]
The fruiting bodies, or ascomata, of Megalaria are sessile apothecia, meaning they are directly attached to the thallus without a stalk. These apothecia are relatively large and black, and they do not have a margin formed from the thallus (known as a thalline margin ). Instead, the edge of the apothecium is made up of the true exciple , which is a layer of hyphae (fungal filaments) arranged in a vertical or anticlinal manner. These hyphae are coated in a thick gel. The hymenium (the spore-producing tissue) of the apothecia is generally colourless to pale brown, while the upper layer, called the epithecium , contains pigments that turn from greenish to dark purple when treated with potassium hydroxide solution (K+). The layer beneath the hymenium, the hypothecium , often shares this greenish to purple colouration, though it can sometimes appear pale. [6]
The interior of the apothecia, or hamathecium , contains numerous slender paraphyses, which are thread-like sterile cells that can be either unbranched or slightly branched. Their tips are club-shaped, but they lack the dark caps sometimes seen in other lichens. The asci (spore-producing sacs) are typically cylindrical to club-shaped and contain between two to eight spores. These asci are of the Lecanora -, Bacidia -, or Biatora -type, which means they feature a broad, non-reactive (non-amyloid) apical cushion and a distinct ocular chamber. [6]
The spores produced by Megalaria are generally ellipsoidal in shape, divided by one internal septum (1-septate), colourless, and smooth with thick walls. Unlike some other lichen spores, they do not have a distinct outer sheath. In addition to its sexual reproductive structures, Megalaria also produces asexual spores, or conidia, in structures called pycnidia. These conidia are colourless and can be ellipsoidal to cylindrical in shape. [6]
Chemical spot tests generally do not detect any products in Megalaria species, although some species can produce secondary metabolites such as atranorin, zeorin, and fumarprotocetraric acid. [6]
As of October 2024 [update] , Species Fungorum (in the Catalogue of Life) accepts 44 species of Megalaria. [2]
The Ramalinaceae are a family of lichen-forming fungi in the order Lecanorales. First proposed by Carl Adolph Agardh in 1821, the family now comprises 63 genera and about 750 species. Ramalinaceae lichens exhibit diverse growth forms, including crustose, fruticose, squamulose, leprose, and byssoid thalli, and form symbiotic relationships primarily with green algae of the genus Trebouxia. The family is characterised by pale-coloured thalli, apothecia that are typically pale but may darken with age, and ascospores that vary in shape and septation.
Bacidia is a genus of lichen-forming fungi in the family Ramalinaceae. The genus was circumscribed by Giuseppe De Notaris in 1846.
Ochrolechia is a genus of crustose lichens in the family Ochrolechiaceae. These lichens typically form uneven, often thick, crust-like growths on various surfaces and are characterised by their white to pale grey thalli, which may have a greenish tint. The genus has a long evolutionary history, with fossils dating back to the Paleogene period, about 34 million years ago. Ochrolechia species have disc-like apothecia, which are usually yellowish or brownish-pink and often covered with a fine white powdery coating. The genus is widely distributed and includes both common and rare species, with some found in extreme environments such as arctic and alpine regions. Ochrolechia lichens produce diverse secondary metabolites, including orcinol depsides, depsidones, and xanthones.
Ramalina is a genus of greenish fruticose lichens that grow in the form of flattened, strap-like branches. Members of the genus are commonly called strap lichens or cartilage lichens. Apothecia are lecanorine.
Acanthothecis is a genus of lichen-forming fungi in the family Graphidaceae. The genus was circumscribed by Frederick Edward Clements in 1909.
Cladia is a genus of lichen-forming fungi in the family Cladoniaceae. Cladia species have a crustose or squamulose (scaly) primary thallus and a fruticose, secondary thallus, often referred to as pseudopodetium. The type species of the genus, Cladia aggregata, is widely distributed, occurring in South America, South Africa, Australasia and South-East Asia to southern Japan and India. Most of the other species are found in the Southern Hemisphere.
Herteliana is a genus of lichen-forming fungi. It contains four species of crustose lichens.
Schadonia is a genus of lichen-forming fungi. Established by German lichenologist Gustav Wilhelm Körber in 1859, this genus of crustose lichens is characterised by its black, sessile apothecia, muriform ascospores, and growth on mosses, plant debris, and rocks in montane habitats. While traditionally placed in the family Ramalinaceae, recent studies have suggested its classification may be uncertain within the order Lecanorales, with some researchers proposing its placement in the Pilocarpaceae or the resurrection of the family Schadoniaceae. The genus currently comprises four recognised species.
Arthothelium is a genus of lichen-forming fungi in the family Arthoniaceae.
Punctelia is a genus of foliose lichens belonging to the large family Parmeliaceae. The genus, which contains about 50 species, was segregated from genus Parmelia in 1982. Characteristics that define Punctelia include the presence of hook-like to thread-like conidia, simple rhizines, and point-like pseudocyphellae. It is this last feature that is alluded to in the vernacular names speckled shield lichens or speckleback lichens.
Ramboldia is a genus of lichen-forming fungi in the family Ramboldiaceae. The genus was circumscribed in 1994 by Gintaras Kantvilas and John Alan Elix. It was emended in 2008 by the inclusion of Pyrrhospora species containing the anthraquinone russulone in their apothecia and having a prosoplectenchymatous exciple. The family Ramboldiaceae was circumscribed in 2014 to contain the genus.
Rhizocarpon is a genus of crustose, saxicolous, lecideoid 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.
Catillaria is a genus of crustose lichens in the family Catillariaceae. The genus was circumscribed by Italian lichenologist Abramo Bartolommeo Massalongo in 1852. It is the type genus of Catillariaceae, which was circumscribed by Austrian lichenologist Josef Hafellner in 1984.
Roccellinastrum is a genus of lichen-forming fungi in the family Pilocarpaceae. It has seven species.
Lepra is a genus of lichen-forming fungi in the family Pertusariaceae. Although the genus was created in 1777, it was not regularly used until it was resurrected in 2016 following molecular phylogenetic analyses. It has more than a hundred species, most of which were previously classified in genus Pertusaria.
Piccolia is a small genus of crustose lichens in the class Lecanoromycetes. First circumscribed by Italian lichenologist Abramo Bartolommeo Massalongo in 1864, it contains ten species. Due to a lack of molecular data, it has not been assigned to an order or family.
Crocodia is a genus of foliose lichens in the family Peltigeraceae. It has eight species. The genus has a cosmopolitan distribution, although most species occur in temperate and tropical regions of the Southern Hemisphere. The main characteristics of the genus that separate it from its parent genus, Pseudocyphellaria, include a yellow medulla and yellow pseudocyphellae on the lower thallus surface.
