The supraspecific taxonomy and evolution of the fern genus Azolla (Azollaceae)

The systematics of the aquatic fern genus AzollaLam. is revised at the supraspecific level. Published morphological data are reviewed, and cytological and cladistic analyses of the genus conducted, enabling a discussion of the putative evolutionary trends in the genus, and a revision of the current taxonomy. A phylogenetically more acceptable subgeneric and sectional classification is proposed, viz. subg. Azolla sect. Azolla (comprising A. filiculoidesLam., A. rubraR. Br., A caroliniana auct. non Willd., A. microphylla auct. non Kaulf. and A. mexicanaPresl), subg. Azolla sect. Rhizosperma (Mey.)Mett. (comprising A. pinnataR. Br.), and subg. Tetrasporocarpia subg. nov. (comprising A. niloticaDecne. ex Mett.). © 1993 Springer-Verlag.link_to_subscribed_fulltex