Azolla (commonly called mosquito fern, water fern, and fairy moss) is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, having a significantly different appearance to other ferns and more resembling some mosses or even duckweeds. Azolla filiculoides is one of two fern species for which a reference genome has been published. It is believed that this genus grew so prolifically during the Eocene (and thus absorbed such a large amount of carbon) that it triggered a global cooling event that has lasted to the present.
Azolla may establish as an invasive plant in areas where it is not native. In such a situation, it can alter aquatic ecosystems and biodiversity substantially by exhausting oxygen and covering water surface making underwater plants unable to photosynthesise.
Phylogeny
Phylogeny of Azolla
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Azolla
A. nilotica Decne. ex Mett. (Nile Azolla)
A. filiculoides Lam. (Large mosquito fern)
A. rubra R.Br.
A. caroliniana Willdenow 1810 (Eastern/Carolinian mosquito fern)
A. cristata Kaulf. (Mexican mosquito fern)
A. pinnata R.Br. (Ferny/Pacific Azolla; Feathered mosquitofern)
Other species include A. mexicana.
At least six extinct species are known from the fossil record:
