Thelenellaceae is a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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 ...

. It is the sole family in the

monotypic 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 "unisp ...

order Thelenellales, and contains three genera and about 50 species.

Taxonomy

The family was initially proposed by Ove Erik Eriksson, and later formally published by Helmut Mayrhofer in 1987. The order Thelenellales, containing only family Thelenellaceae, was proposed by H. Thorsten Lumbsch and Steven Leavitt in 2018. However, the taxon was not

validly published In botanical nomenclature, a validly published name is a name that meets the requirements in the ''International Code of Nomenclature for algae, fungi, and plants'' (''ICN'') for valid publication. Valid publication of a name represents the minim ...

because "an identifier issued by a recognized repository was not cited in the protologue", contrary to rules of

botanical nomenclature Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy (biology), taxonomy. Plant taxonomy is concerned with grouping and classifying plants; Botany, botanical nomenclature then provides na ...

. This nomenclatural oversight was rectified later the same year in a separate publication. Family Aspidotheliaceae, proposed to contain the single genus ''Aspidothelium'', was later expanded to include ''Musaespora''. Nelsen and colleagues, in their studies published in 2009 and 2011, observed only minimal differences between the Aspidotheliaceae and Thelenellaceae, suggesting the possibility of merging them into a single family. Harris, in 1995, already treated Aspidotheliaceae and Thelenellaceae as one family, alongside the genus '' Celothelium'', while Eriksson and Hawksworth in 1998 proposed retaining Aspidotheliaceae as a separate entity until more taxa could be examined. Using

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 ...

analysis, Nelsen and colleagues showed in 2017 that ''Aspidothelium'' is embedded within the family Thelenellaceae, and thus

synonymous A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

with it.

Description

Family ''Thelenellaceae'' comprises lichens with a

crustose Crustose is a Habit (biology), 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 Substrate (biology), substrates at all poin ...

thallus, which means the lichen forms a crusty, spread-out layer that appears effuse and sometimes breaks into small, angular patches known as . The photosynthetic partner () within these lichens is , a type of

green alga 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 ( ...

. The reproductive structures,

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 ...

, are in form, either sitting freely () or slightly embedded in thalline warts on the lichen's surface. These structures are thick-walled and can be smooth, warted, or ridged, often featuring a broad apical shield and varying in colour from pale to dark brown. The opening of the ascomata, or

ostiole An ''ostiole'' is a small hole or opening through which algae or fungi release their mature spores. The word is a diminutive of wikt:ostium, "ostium", "opening". The term is also used in higher plants, for example to denote the opening of the ...

, is surrounded by , hair-like structures that help protect and support the ascomata. Internally, the ''Thelenellaceae'' family's ascomata contain a made up of narrow, branched, and interconnected , which are filamentous structures within the ascomata. Asci, the spore-producing cells, are thick-walled and may have a small ocular chamber at their apex, but they do not turn blue when stained with

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

. The produced are colourless, thin-walled, and may be transversely

septate In biology, a septum (Latin for ''something that encloses''; septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatrial se ...

(divided by cross-walls) or (divided by both cross and longitudinal walls), often developing a median septum within each cell. Some ascospores are surrounded by a gelatinous sheath. For asexual reproduction, ''Thelenellaceae'' lichens produce

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 ...

, which are small flask-shaped structures that generate asexual spores called

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 ...

. These conidia are cylindrical, lack septa, and are colourless. There are no

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 ...

s (

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) that are known to occur in the family.

Genera

This list of genera in the Thelenellaceae is based on a 2021 review and summary of fungal

classification Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identif ...

by Wijayawardene and colleagues. Following the genus name is the

taxonomic authority In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given ...

(those who first

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 ...

the genus; standardised author abbreviations are used), year of publication, and the number of species: *'' Aspidothelium'' – 17 spp. *'' Chromatochlamys'' – 3 spp. *'' Thelenella'' – 30 spp. '' Julella'' is a poorly known genus of non-lichenised fungi that is tentatively included in the Thelenellaceae by some sources, while other sources include it in the

Trypetheliaceae The Trypetheliaceae are a family of mainly lichen-forming fungi in the order Trypetheliales. The family consists almost exclusively of corticolous (bark-dwelling), crustose lichens with an almost strictly tropical distribution. Taxonomy Trypethe ...

or as a genus of "unconfirmed affinities". In their 2021 treatment of the Thelenellaceae in the ''Revisions of British and Irish Lichens'' series, Cannon and Orange suggest that there is "no convincing morphological distinction between" the genera ''Chromatochlamys'' and ''Thelenella'', and they consider ''Thelenella'' in a broad sense to include ''Chromatochlamys''.

Habitat and distribution

Lichens in the family grow on bark, on leaves, on bryophytes, or on rocks. Collectively, the species in the family have a widespread distribution.

References

{{Authority control Lecanoromycetes Lecanoromycetes families Lichen families Taxa described in 2018 Taxa named by Helge Thorsten Lumbsch