Comprehensive Description

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Comprehensive Description

Chara vulgaris is a green alga belonging to the Charales, a lineage that may have given rise to all land plants. It has long been recognized that land plants evolved from green algae. Traditionally, two groups of green algae have been recognized, the Chlorophyta (e.g., Fritschiella, Oedogonium, and Ulothrix) and the charophycean (or charophytic) green algae (e.g., Chara, Coleochaete, and Spirogyra). Since around 1970, there has been a clear scientific consensus that the land plants (both vascular and non-vascular) emerged from within the charophyceans, not from the chlorophytes (this consensus has been greatly strengthened by several molecular phylogenetic studies in recent years). The Chlorophyta is a monophyletic group (i.e., a group that includes an ancestor and all its descendants). The charophycean green algae, however, form a paraphyletic group (i.e., a named group that does not include all the descendants of its most recent common ancestor). The reason this named group is paraphyletic is that it excludes the land plants, despite the fact that it seems clear that land plants are in fact nested within the charophyceans. The monophyletic group consisting of the charophycean algae plus all land plants is known as the Streptophyta and represents one of the main lineages of multicellular eukaryotes (the monophyletic Chlorophyta, the non-charophycean green algae, is sister to the monophyletic Streptophyta). The monophyletic group (Chlorophyta + Streptophyta) is known as the Viridiplantae ("green plants"). (Lewis and McCourt 2004; Qiu 2008 and references therein)

For some years there was a widespread consensus, based on a range of ultrastructural, biochemical, and molecular phylogenetic data, that the charophycean Charales (to which Chara vulgaris belongs) is the extant lineage closest to the land plants, but some recent studies have suggested other charophycean lineages as more likely candidates (e.g., Turmel et al. 2007). In recent phylogenetic analyses, the Charales, Coleochaetales, and Zygnematales have each been identified as sister to the land plants, depending on the gene(s) analysed and the taxon sampling, but none of these topologies has had very convincing statistical support. Thus, the question of which extant charophycean lineage is closest to the land plants remains unresolved, although many specialists still favor the Charales. (Lewis and McCourt 2004; Qiu 2008 and references therein; Becker and Marin 2009).

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