Requienellaceae

Taxonomy

Requienellaceae was circumscribed by Jean Boise in 1986, based on studies conducted during research on the genus Trematosphaeria. The family was established within the order Melanommatales (sensu Barr) or Pyrenulales (sensu Eriksson and Hawksworth). The type genus is Requienella, which was originally proposed by Jean-Henri Fabre in 1883. The genus name was sometimes mistakenly spelled as "Requinella" in early mycological literature, including Ainsworth and Bisby's Dictionary of the Fungi (1943).

When first describing the family, Boise designated Requienella seminuda as the type species of both the genus and family. This species was previously known under various names, including Sphaeria seminuda and Requienella olearum. A significant taxonomic clarification made in the original 1986 publication was that the common concept of "Sphaeria seminuda" at that time (based on Fuckel's Fungi rhenani 2319) actually referred to a different fungus belonging to the genus Melanomma.

The genus Trematomyces was established for R. olearum and R. lichenopsis but was later determined to be synonymous with Requienella. Similarly, Acrocordiella was initially described as a separate genus but is now considered part of the Requienellaceae.

Description

Requienellaceae fungi are characterized by several distinctive features of their reproductive structures. They produce dark, spherical fruiting bodies (ascomata) that are typically 0.5–1.25 mm in diameter. These structures are initially embedded within or beneath the bark of their host plants, with the surrounding tissue becoming blackened. Over time, they emerge through the bark's surface.

A key characteristic of this family is their unique internal structure. They possess unbranched, sparsely septate pseudoparaphyses (sterile threads between the spore-producing cells) and specialized spore-producing cells called asci. The asci have a distinctive broad cylinder of material at their tips that responds distinctively to certain biological stains. This feature helps distinguish them from related fungi.

The spores () produced by these fungi are brown in color and have multiple compartments separated by special cross-walls called . These spores show bilateral symmetry, meaning they are mirror images along their middle. In Requienella seminuda, the type species of the family, the spores typically contain 4–8 compartments and measure 20–34 μm in length.

Members of Requienella are typically found growing on the bark of various trees, including olive trees (Olea), ash trees (Fraxinus), and cherry trees (Prunus). They are not known to form lichens with algae, existing independently as fungi.

Genera

The 2024 Outline of Fungi include 16 species distributed amongst 4 genera in the Requienellaceae:

• Acrocordiella – 4 spp.
• Lacrymospora – 1 spp.
• Parapyrenis – 8 spp.
• Requienella – 3 spp.

References

References

1. (2007). "Fungal Families of the World". CABI.
2. (2024). "The 2024 Outline of Fungi and fungus-like taxa". Mycosphere.
3. Aptroot, A.. (1991). "A monograph of the Pyrenulaceae (excluding ''Anthracothecium'' and ''Pyrenula'') and the Requienellaceae, with notes on the Pleomassariaceae, the Trypetheliaceae, and Mycomicrothelia (lichenized and non-lichenized ascomycetes)". Bibliotheca Lichenologica.
4. Boise, Jean. (1986). "Requinellaceae, a new family of Loculoascomycetes". Mycologia.
5. Eriksson, O.. (1982). "Notes on ascomycetes and coelomycetes from NW Europe". Mycotaxon.
6. Fabre, J.H.. (1883). "Essai sur les Sphériacées du Départment de Vaucluse II". Annales des Sciences Naturelles Botanique.