Green algae and the origin of land plants

Over the past two decades, molecular phylogenetic data have allowed evaluations of hypotheses on the evolution of green algae based on vegetative morphological and ultrastructural characters. Higher taxa are now generally recognized on the basis of ultrastructural characters. Molecular analyses have...

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Bibliographic Details
Published inAmerican journal of botany Vol. 91; no. 10; pp. 1535 - 1556
Main Authors Lewis, Louise A., McCourt, Richard M.
Format Journal Article
LanguageEnglish
Published United States Botanical Soc America 01.10.2004
Botanical Society of America
Botanical Society of America, Inc
Subjects
Algae
Characeae
Charales
Charophyta
Chlorophyceae
Chlorophyta
Data analysis
Deoxyribonucleic acid
DNA
Evolution
Flowers & plants
Genera
Genetics
Green algae
Hypotheses
Invited Special Papers
Mesostigma
Phycology
Phylogeny
Plantae
Plants
Prasinophyceae
Ribosomal DNA
Streptophytina
Taxa
Trebouxiophyceae
ultrastructure
Ulvophyceae
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Summary:Over the past two decades, molecular phylogenetic data have allowed evaluations of hypotheses on the evolution of green algae based on vegetative morphological and ultrastructural characters. Higher taxa are now generally recognized on the basis of ultrastructural characters. Molecular analyses have mostly employed primarily nuclear small subunit rDNA (18S) and plastid rbcL data, as well as data on intron gain, complete genome sequencing, and mitochondrial sequences. Molecular-based revisions of classification at nearly all levels have occurred, from dismemberment of long-established genera and families into multiple classes, to the circumscription of two major lineages within the green algae. One lineage, the chlorophyte algae or Chlorophyta sensu stricto, comprises most of what are commonly called green algae and includes most members of the grade of putatively ancestral scaly flagellates in Prasinophyceae plus members of Ulvophyceae, Trebouxiophyceae, and Chlorophyceae. The other lineage (charophyte algae and embryophyte land plants), comprises at least five monophyletic groups of green algae, plus embryophytes. A recent multigene analysis corroborates a close relationship between Mesostigma (formerly in the Prasinophyceae) and the charophyte algae, although sequence data of the Mesostigma mitochondrial genome analysis places the genus as sister to charophyte and chlorophyte algae. These studies also support Charales as sister to land plants. The reorganization of taxa stimulated by molecular analyses is expected to continue as more data accumulate and new taxa and habitats are sampled.
Bibliography:Authors contributed equally to this work.
louise.lewis@uconn.edu
The authors thank F. Zechman, M. Fawley, C. Lemieux, C. Delwiche, E. Harris, and R. Chapman for helpful advice and unpublished data. We are greatly appreciative of F. Trainor and two anonymous reviewers who provided extensive comments on the manuscript. Kyle Luckenbill did the line drawing artwork, and Stéphane Marty prepared the color plate and cell images. The authors acknowledge support from National Aeronautics and Space Administration to LAL (EXB02–0042–0054) and the National Science Foundation to RMM (DEB 9978117).
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ISSN:0002-9122
1537-2197
DOI:10.3732/ajb.91.10.1535