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ABSTRACT
A formal cladistic analysis of the morphological features of taxa assigned to the Orthoseiraceae, including Phycavernosa, Guarreraea and species of the genus Orthoseira is developed for 35 taxa based on 16 characters along with two Melosira species and four biddulphioid species as ingroup taxa as well as Leptocylindrus danicus as the outgroup. A consensus tree of 266 843 most parsimonious topologies suggests that the Orthoseiraceae is monophyletic, and that Guarreraea plus all former species of Orthoseira represent a monophyletic group. This analysis of morphological data did not provide support for the members of the Orthoseiraceae being more closely related to melosiroid or biddulphioid diatoms. Relationships within the monophyletic orthoseiracean group are detailed. Due to the exclusion of the generitype of Orthoseira not possessing carinoportulae which are central tube processes, one of the diagnostic features of the former Orthoseiraceae, other taxon names are described and recognized herein. We recognize and describe a new order, the Liparogyrales, based on the genus Liparogyra for taxa that were previously assigned to Orthoseira. Two families, the Phycavernosaceae, comprising the genus Phycavernosa, and the Liparogyraceae, comprising Guarreraea and taxa formerly assigned to Orthoseira, are described. The genus Liparogyra is composed of three subgenera: the subgenus Liparogyra, the subgenus Porocyclia, and the subgenus Insularis which are diagnosed by synapomorphic features. Based on our analysis, the genus Stephanosira appears to lack synapomorphies. Liparogyra, Porocyclia and Stephanosira had previously been described as genera by Ehrenberg. Guarreraea and one newly proposed genus are also included in the Liparogyraceae. Several other lineages are aphyletic, due to them either being monotypic or without diagnostic features. Thus, a total of 29 species in five genera are recognized within the newly described order and two newly described families. Eighteen new combinations are proposed for the transfer of taxa from Orthoseira to other genera. Homoplasy amongst some of the character states is discussed.
Highlights
The diatom genus Orthoseira as typified by O. americana does not possess carinoportulae, requiring a new approach to the nomenclature and taxonomy of the group.
A phylogenetic analysis of the group using morphological data was performed, demonstrating patterns of relationships of the species for this lineage.
A new classification for this diatom lineage is presented.
Acknowledgements
We would like to thank the two anonymous reviewers of this manuscript for their valuable feedback and constructive criticism. Their comments clarified the intention, language and scope of this work. We would also like to thank Dr Wiebe Kooistra and Dr Juliet Brody for their final comments, and for their help in preparing this manuscript for publication. Their comments helped make this manuscript more cohesive and concise.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Author contributions
A. Danz: participated in the development of the project, carried out the analysis, did the majority of the writing of the manuscript and participated in the revisions; J.P. Kociolek: participated in the development of the project, writing and review of the manuscript and in its revisions; B. Vde Vijver, W-H. Kusber, J. Guerrero, A. Vouilloud and S. Sala: participated in writing and review of the manuscript, and in the preparation of the revisions.