Coenogonium Explained

Coenogonium is a genus of filamentous lichens in the monotypic family Coenogoniaceae. It has about 90 species. Most species are leaf-dwelling or grow on bark, although a few are known to grow on rocks under certain conditions, and some are restricted to growth on termite nests. The genus was circumscribed in 1820 by German naturalist Christian Gottfried Ehrenberg.

Coenogonium has a worldwide distribution, with most species known from tropical areas. Most species grow in tropical rainforests in the shaded understorey. They typically grow on tree trunks, branches, lianas, and leaves.

Description

Although members of Coenogonium are relatively easy to identify given its unique characteristics, identifying to species is more difficult due to the slight differences between them. The genus is characterized by (rarely), yellow to orange or brown apothecia with a excipulum, partially amyloid hymenium (I+ blue then quickly sordid green then red-brown), thin-walled unitunicate asci, and 1-septate or rarely non-septate ascospores. The photobiont component of Coenogonium is a green alga from the family Trentepohliaceae. The structure of the Coenogonium thallus is largely determined by the algal partner.

Similar genera include Malcolmiella, which differs mainly by having amyloid asci with a thickened and non-septate, usually longer and broader ascospores with an ornamented ; Absconditella, which has a photobiont and non-amyloid asci; and Cryptodiscus, which has Gloeocystis as photobiont, amyloid asci with a thickened apex and non-septate paraphyses.

Research

Species of Coenogonium have frequently used in morphological/anatomical and ecophysiological studies. Examples include thallus growth, apothecial development, ultrastructure, photobiont and resynthesis in culture, and photosynthesis. The filamentous thalli of Coenogonium serve as a home for diatoms and other microorganisms. Johannes Müller Argoviensis even used his erroneous interpretation of the thallus organization of filamentous Coenogonium to oppose Simon Schwendener's theory of the symbiotic nature of lichens.

Species

The genus is well known in continental areas that border the Caribbean, such as Florida and Costa Rica. About half of the world's biodiversity of this genus occurs in Brazil.

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