The Naming of Lichens

This is really just out of curiosity and I know there are lichen-lovers out there!

My introduction and exposure to lichens has so far been to just look for something to iNat during winter times when insects are less active. Though I have recently learnt that lichens are a composite organism consisting of a symbiosis between a fungus and an alga or a fungus and a cyanobacteria (and I guess a combo too).

So do lichen binomials (eg. Flavoparmelia caperata) refer to the composite organism? If yes, does that “break” the many “unofficial rules” of what defines a species? And do the fungus, alga and/or cyanobacteria that make up the lichen have their own individual binomials as well? Or are they do dependent on each other that its just better to bundle them all in one?

Thanks for the answers and the potential discussion.


It’s not exactly a symbiosis, fungi catch algae and the latter doesn’t really like it, algae and cyanobacteria do live freely out of lichens (you can find names of them for different groups of lichen, e.g. Trebouxia) fungi need them to properly live. Name is for fungi.
I’m sure @jurga_li can explain it better.


Yes, as @melodi_96 said, the binomial given to a lichen refers solely to the fungal partner. Algal and cyanobacterial partners each get their own scientific names.

I think it has been shown that some species/strains of photobionts are only really found in lichens, though, and not free living. The symbiosis might not exactly be mutualism, but in those cases it seems like it has been a decent survival strategy.

For an additional bit of interest regarding these composite organisms, it has also been shown that lichen thalli host a lot of different bacteria and even other fungi, as well.


We also do not break any nomenclature rules by calling ourselves Homo sapiens, even though we also have a huge array of gut endosymbionts (and also there is a different code governing the naming of animals… lichen and fungal nomenclature falls under the Code of Botanical Nomenclature, even though fungi are more closely related to animals than plants).


Well, starting from the classics: it is not so simple…
Yes, lichens are composite organisms, or more truly, microecosystems, where many individuals and even several species of fungi can be found in one thallus with addition of many individuals of algae or cyanobacteria, or even algae and cyanobacteria together with some other bacteria, too. Role and relationships of some of these are comparatively well known or totally unknown. Lichen symbiosis at its best is indeed mild parasitism with only slight benefits for the photobionts. But then, all fungal “symbioses” are indeed some kind of parasitism.
Yes, lichens are named after the mycobiont - the main fungus, algae and cyanobacteria have their own names,so do the rest of legal and illegal inhabitants. But here the simple part ends.@robotpie asked: So do lichen binomials (eg. Flavoparmelia caperata) refer to the composite organism? And the answer is: mostly, yes. Because all descriptive names or parts of binominals that refer to thallus, refer to the composite product. Because fungus alone will never create anything like the lichens we know. It can grow as an amorphous mass, but never produce thallus. So Flavoparmelia caperata refers to the product of symbiosis: yellow (flavus) wrinkled (caperatus) thallus. @mftasp Homo sapiens could not live without its microbiome, but it would still have form of Homo sapiens.


I think if we talk about complex organisms no eukariote organism is in fact a single organism, so names we use are always for something bigger than one set of DNA.


Very interesting, thanks for all your answers. So far my relationship with lichens is just wavering curiosity but I learnt more things from your replies so I am appreciative of that.

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Yeah the question I posed wasn’t exactly a good one, I intended it to be like a supplemental to my first one. Good example of disproof by counterexample!

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So I’m assuming due to the naming of lichens being for the fungus, that is why they are placed (at least in iNat) under Fungi.

(I’m also beginning to realize a lot of these questions can be answered via a read through Wikipedia)

And also why, unless you know a narrower ID for your particular fungus, you cannot ID it as just “Fungi,” but only as “Fungi including Lichens.” Presumably, this means that lichen-forming fungi and non-lichen forming fungi are not two neat clades.

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You can use fungi id, you can use ascomycota for most of lichens, but some are in basidiomycota. They’re not like sister clades to other fungi, but lichens are totally different groups within others. English common name is there to help people find where their lichens belong to.

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I do recall iNat has a “Fungi including lichens” selection but that doesn’t seem to appear for me now.

I found this, is it it or there was really more than that? image


This is right, because lichenization occured in different lineages of fungi and sometimes it occurred several times during evolutionary process. There are higher taxonomic entities (mostly families) that include only lichenized members, others include both. In some, lichenized members prevail, in others there are only few lichens. Name Fungi including lichens here is for convenience purpose only (and a very good idea!),because many people would not know where to place lichens otherwise. Quite a few still place them in Plants.


Yeah, since the scientific name is for their primary fungi component, they’re classified based on that as well. Lichens aren’t a single group taxonomically, but identifiers have told me that they prefer if I identify my lichens as class Lecanoromycetes, which covers most of them.

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