The Arthoniales is the second largest order of mainly

crustose Crustose is a habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. ''Crustose'' adheres very closely to the substrates at all points. ''Crustose'' is found on rocks and ...

lichens, but

fruticose A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy growth structure. It is formed from a symbiotic relationship of a photobiont such as green algae or less commonly cyanobacteria and one, two or mor ...

lichens are present as well. The order contains around 1500 species, while the largest order with lichenized fungi, the

Lecanorales The Lecanorales are an order of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. The order contains 26 families, 269 genera, and 5695 species. Families * Aphanopsidaceae * Biatorellaceae * Brigan ...

, contains more than 14000 species.

Classification

The Arthoniales is one of two

orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

of the class

Arthoniomycetes Arthoniomycetes are a class of ascomycete fungi. It includes two orders: Arthoniales and Lichenostigmatales. Most of the taxa in these orders are tropical and subtropical lichens. Systematics Phylogenetic analysis supports the monophyly ...

within the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

. The order includes seven families ( Andreiomycetacae, Arthoniaceae, Chrysotrichaceae, Lecanographaceae, Opegraphaceae,

Roccellaceae The Roccellaceae are a family of fungi in the order Arthoniomycetes. Most taxa are lichenized with green algae, although some are lichenicolous, growing on other lichens. Genera , Species Fungorum (in the Catalogue of Life) accepts 47 genera an ...

and Roccellographaceae). Lecanographaceae, Roccellographaceae, Opegraphaceae and Roccellaceae are well-supported families within Arthoniales, and they were circumscribed in 2011. Andreiomycetaceae was described as a new family by Hodkinson and Lendemer in 2013. The Arthoniales is the sister group to

Dothideomycetes Dothideomycetes is the largest and most diverse class of ascomycete fungi. It comprises 11 orders 90 families, 1300 genera and over 19,000 known species. Traditionally, most of its members were included in the loculoascomycetes, which is not par ...

. Figure 1. Cladogram of the Arthoniales, rooted with ''Curvularia brachyspora'', ''Cudonia circinans'' and ''Seynesia erumpens'' as the outgroup. The cladogram shows the division of Arthoniales into seven families, based on Hodkinson et al. 2013.

Distribution and habitats

The Arthoniales is distributed in most habitats worldwide, as it ranges at latitudes from arctic to tropical regions. They grow on different types of substrates like bark, wood, rocks, bryophytes and living leaves. The order has adapted to live in both humid forests and dry habitats like savannas and steppes, as well as varying altitudes from sea level to alpine regions. The highest species diversity are known from subtropical coastal areas with a Mediterranean or dry climate. The species diversity of the Arthoniales is expected to be higher than currently reported from several areas worldwide like the tropical rain forests.

Ecology

The majority of species in Arthoniales have a lichenized lifestyle, but

lichenicolous A lichenicolous fungus is a parasitic fungus that only lives on lichen as the host. A lichenicolous fungus is not the same as the fungus that is the component of the lichen, which is known as a lichenized fungus. They are most commonly specific to ...

and

saprophytic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...

species are presented as well. The original state in the Arthoniales is believed to be the lichenized state, and the non-lichenized and parasitic states have evolved independently several times. The lichenized fungi live in symbiosis with a

photobiont A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.Trentepohliaceae Trentepohliaceae are a family of green algae in the order Trentepohliales Trentepohliales is an order (biology), order of Ulvophyceaen green algae.See the National Center for Biotechnology Information, NCBI]webpage on Trentepohliales Data ext ...

, but photobionts from Chlorococcaceae, Chlorococcaleae are known from Chrysotrichaceae and a few species in '' Arthonia''.

Characters

It is difficult to mention typical morphological characters like fruit body, exiple, hypothecium,

hymenium The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some ...

, chemistry, ascospore color and ascospore septation that can be used as uniting traits for delimiting families and genera in the Arthoniales. The reason is that the Arthoniales is an old order and taxa have evolved in parallel for a long time, which gives a high level of homoplasy.

Ascomatal anatomy

The ascomata are usually apothecial and it produces bitunicate asci. The bitunicate asci are thick-walled, with an outer and inner layer. The outer and inner layer of the ascus wall are called exotunica and endotunica, and they separate during ascospore release. The asci usually contains eight ascospores, while the shape and separation of the ascospores are more variating.

Thallus

The majority of the species in Arthoniales are crustose lichens, with a thallus growing tight to the surface. Fruticose lichens have a bushy thallus and are known in Roccellaceae, where it has evolved and been lost multiple times. The thalli among crustose lichens can either grow within the substrate, called endophloedal or it can grow at the surface of the substrate, called epiphloedal.

Genera ''incertae sedis''

Bactrospora brevispora - Flickr - pellaea (1)

The following

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

have been tentatively classified in the Arthoniales but have not been placed with any certainty into a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

. *'' Angiactis'' – 3 spp. *'' Arthophacopsis'' – 1 sp. *'' Bactrospora'' – 35 spp. *'' Bryostigma'' – 3 spp. *'' Catarraphia'' – 1 sp. *'' Felipes'' – 1 sp. *'' Glyphopsis'' – 1 sp. *'' Gossypiothallon'' – 1 sp. *'' Helminthocarpon'' – 3 spp. *'' Hormosphaeria'' – 1 sp. *'' Minksia'' – 2 spp. *'' Nipholepis'' – 1 sp. *'' Paradoxomyces'' – 1 sp. *'' Perigrapha'' – 5 spp. *'' Phacothecium'' – 1 sp. *''

Phoebus Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...

'' – 1 sp. *'' Sporostigma'' – 1 sp. *'' Synarthonia'' – 5 spp. *'' Synarthothelium'' – 2 spp. *'' Tarbertia'' – 1 sp. *'' Trichophyma'' – 2 spp. *'' Tylophorella'' – 1 sp. *'' Wegea'' – 1 sp.

References

{{Taxonbar, from=Q148747 Arthoniomycetes Lichen orders Ascomycota orders Taxa named by David Leslie Hawksworth Taxa described in 1986