Abstract
Lichens are fungi (mycobionts) that form symbiotic associations with photoautotrophic prokaryotes or eukaryotes (photobionts); however, some species can exchange photosynthetic partners during their lifecycles. This phenomenon modifies the morphology of lichens and consequently influences the taxonomy of lichenized fungi. Here, a few such cases in which the photobionts influenced the taxonomy and systematics of lichenized fungi are reviewed. Two different morphotypes of the same species – known as photomorphs – were classified as different species and sometimes different genera. Moreover, different types of photobionts and the absence or presence (optional lichenization) of an alga in the thallus were believed to be diagnostic characters for discriminating genera. However, the taxonomy and systematics of lichens are based always, according to Article F.1.1. of the <em>International </em><em>Code of Nomenclature for Algae, Fungi, and Plants</em>, on the fungal partner and only one name is applied.
Highlights
Lichens, known as lichenized fungi, are an iconic example of symbiosis and belong to Ascomycota Caval.-Sm. or Basidiomycota R
The mycobiont is associated with one or more photosynthetic partners, which may belong to eukaryotic green algae or prokaryotic cyanobacteria (e.g., Dal Grande et al, 2017; Friedl & Büdel, 2008; Lücking et al, 2009; Moya et al, 2017; Onut,Brännström et al, 2018; Purvis, 2000)
The third group probably does not play any ecological role in lichen symbiosis; these lichen thalli may serve as banks of spores and mycelia or reservoirs of the local fungal mycobiome (Fernández-Mendoza et al, 2017)
Summary
Known as lichenized fungi, are an iconic example of symbiosis and belong to Ascomycota Caval.-Sm. or Basidiomycota R. Some lichenized fungi form thalli with other autotrophic groups of organisms, of which cyanobacteria (cyanobionts) are the commonest symbiotic partners (e.g., Lücking et al, 2009, 2017; Miadlikowska et al, 2006, 2018; Tschermak-Woess, 1988, 1989) In some lichens, both types of photobionts can be present in a single thallus, forming a tripartite association, with green algae being the dominant component of the thallus and cyanobionts recruited in cephalodia (e.g., Lamb, 1951; Miadlikowska et al, 2018; Oset & Kukwa, 2012; Schneider et al, 2016; Tønsberg & Goward, 2001). Some examples of the influence of shift in photosynthetic partners on the taxonomy of lichenized fungi are presented
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