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#plant systematics

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Plant Classification

ANA grade includes

ANA stands for Amborellales monotypic Amborella trichopoda endemic New Caledonia, Nymphaeales including Hydatellaceae, Cabombaceae brasenia Cabomba and Nymphaeaceae water lilies, Austrobaileyales comprising Austrobaileyaceae, Schisandraceae e.g., Illicium star anise and Schisandra, Trimeniaceae. Together they form grade of three successive divergences preceding mesangiosperms, not monophyletic clade but paraphyletic assemblage, about 300 species total. Alternative options list magnoliid orders Piperales Laurales Magnoliales Canellales, or monocot families Poaceae Orchidaceae Asparagales, or eudicot clades. Grasping ANA composition essential for understanding ancestral flower reconstruction and evolutionary innovations like carpel closure evolution.

Ref: Campbell Biology, 12th ed., Chapter 30: ANA grade constituents Amborella Nymphaeales Austrobaileyales

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Plant Classification

The most basal angiosperm clade among the following is

Molecular clock analyses and phylogenomic datasets place ANA grade as earliest diverging extant angiosperm branches successive sisters to Mesangiospermae containing all other flowering plants representing about 99.95 percent diversity. Monocots diverge after Austrobaileyales within mesangiosperms, eudicots later forming large clade, magnoliids sister to monocot-eudicot clade forming magnoliids group. Therefore most basal among options remains ANA grade encompassing Amborella, Nymphaeales, Austrobaileyales. This basal position confirmed by plastid genome inversions and mitochondrial gene losses and nuclear single-copy gene phylogenies. Recognition refutes hypothesis magnoliids basal, highlighting importance of phylogenomic rooting using gymnosperm outgroups like Pinus Ginkgo.

Ref: APG IV 2016, Botanical Journal Linnean Society, ANA grade basal angiosperm phylogeny

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