The ANA Grade: The First Flower's Odd Essential Cousins
The ANA Grade: The First Flower's Odd Essential Cousins
If you could rewind the botanical clock to the Early Cretaceous and go for a stroll (take an umbrella; the climate had ideas), you would not find roses, orchids, or sunflowers. You’d meet a much smaller cast of characters—quiet plants keeping their heads down—whose claim to fame is simply being there first. These are the ANA grade plants we discussed last time. The name, ANA grade may sound like a frequent‑flier scheme but is, in fact, three ancient lineages: Amborellales, Nymphaeales, and Austrobaileyales.
A quick word on “grade,” because scientists, like tax accountants, treasure precision. A grade is a rung on the ladder—a set of lineages grouped by overall similarity or level of evolution—but not necessarily a true family circle. A clade is the whole actual branch: one ancestor plus all its descendants. The ANA grade is paraphyletic: it sits at the base of the flowering plant tree but doesn’t include everything that descends from there. We keep the label because it’s useful shorthand for “the first branches we still have around.”
Why care? Because these plants are our living time capsules. They help answer the two questions that haunt anyone who has ever looked at a petunia: how did flowers get started, and why did they take over the planet?
Dating very old events is like trying to reconstruct a dinner party from the stains on the tablecloth. The fossil record for early flowers is spotty, and molecular clocks tick at speeds that inspire polite debate. With that disclaimer:
~140–130 million years ago (Early Cretaceous): The first angiosperms appear. Think modest blooms with spiral parts, unspecialized pollination, and a general air of “making do.”
~130 million years ago: The lineage leading to Amborella peels off from the rest. Most analyses place Amborella as sister to all other living flowering plants.
~125–120 million years ago: Nymphaeales—the water‑lilies, fanworts, and some tiny aquatic oddities—split away and try life afloat.
~120–115 million years ago: Austrobaileyales—woody plants with aromatic oils—diverge from the line leading to the rest of angiosperms.
~110 million years onward: The great diversification: magnoliids, monocots, and eudicots explode into the world we recognize today.
One useful bit of humility: while “Amborella first” is the best‑supported picture, some datasets have suggested alternatives—Nymphaeales first, or an early Amborella+Nymphaeales grade. Science, like a sensible gardener, prunes and reshapes as new growth appears.
We didn’t arrive at this arrangement by staring meaningfully at petals. The evidence comes from three main directions.
Chloroplast DNA
Genes such as rbcL, matK, and atpB, run through big phylogenetic analyses, tend to recover a basal sequence along the lines of: Amborella → Nymphaeales → Austrobaileyales → everyone else. Support varies by dataset, sampling, and model; confidence is high for the broad picture, fuzzier for fine details (the botanical equivalent of being sure you’re in France, less sure which village).
Nuclear genome clues
Amborella trichopoda’s genome delivered a surprise worthy of fireworks: evidence for an ancient whole‑genome duplication near the base of the angiosperms—an extra genetic toolkit that many flowering plants carry in their history. Amborella itself appears to have avoided some of the later duplication binges that plumped up other lineages, which makes its genome a cleaner window into the ancestral state. Also, file under “oddities to dine out on”: Amborella’s mitochondrial genome is a patchwork quilt, having apparently borrowed chunks from mosses and other plants via horizontal gene transfer. Plants, it turns out, are not above a little genomic shoplifting.
Traits you can see
Early‑diverging angiosperms often show features we infer to be ancestral: spiral arrangement of floral organs; indeterminate numbers of tepals, stamens, and carpels; monosulcate pollen (a single furrow; very tasteful); and wood anatomy that hasn’t gone full modern. Amborella, in a wonderfully contrarian move, has no vessel elements in its xylem—only tracheids, much like gymnosperms. Many other early lines (water‑lilies, Austrobaileyales) do have vessels, typically with “primitive” scalariform (ladder‑like) perforation plates—functional, but not the hyper‑efficient plumbing later angiosperms evolved.
The point isn’t just “old things look old.” These traits shaped what early flowers could do: who pollinated them, how they moved water, how flexible their floral development was, and ultimately which habitats they could invade.
Amborellales
Headcount: 1 species, Amborella trichopoda.
Address: New Caledonia’s rainforests, which are where botanical time sometimes forgets to pass.
Personality: Evergreen shrub; small unisexual flowers; simple leaves; no xylem vessels.
Why it matters: As the likely sister to all other living angiosperms, Amborella gives us a comparative baseline—the “before” picture. Its genome preserves signals of that foundational whole‑genome duplication and fewer later rearrangements. Its wood anatomy shows that vessels—the signature pipes of flowering plants—weren’t a day‑one invention.
Nymphaeales (water‑lilies and friends)
Families: Nymphaeaceae (true water‑lilies like Nymphaea, Victoria, Euryale), Cabombaceae (Cabomba, Brasenia), and Hydatellaceae (tiny aquatic herbs).
Headcount: On the order of ~90 species altogether.
Look‑and‑feel: Floating leaves with long petioles, big showy flowers, lots of petals and stamens with a gentle gradient from one to the other. Monosulcate pollen, aquatic habits, and vessels of a more old‑fashioned sort.
Two genuinely memorable tidbits:
Victoria amazonica can support a small child (do not try this; parents frown), and its nightly opening routine is a masterclass in beetle entertainment.
Hydatellaceae were once filed confidently with grasses and sedges (Poales) because they’re tiny and unassuming. Molecular data yanked them, with some embarrassment, into Nymphaeales. Same pond, utterly different ancestry. Taxonomy occasionally has to send out apology notes.
Austrobaileyales:
Families: Austrobaileyaceae (the singular Austrobaileya), Schisandraceae (Illicium, Schisandra, Kadsura), Trimeniaceae (Trimenia and kin).
Headcount: Roughly ~100 species, most in Schisandraceae.
Distinguishing features: Woody plants rich in aromatic oils; often many stamens; carpels with a satisfyingly rugged, early‑angiosperm feel.
Why you’ve met them: Illicium verum is star anise, which turns stews into poetry and is botanically handy for remembering that chemistry—secondary metabolites, scents, oils—was central to early defense and pollination. Aromas attract helpful animals and shoo away the rude ones.
Spiral, indeterminate floral parts: Flexible developmental programs likely made early flowers robust to mutation and environmental variation. You can improvise your orchestra when the score is still being written.
Monosulcate pollen: A no‑frills ancestral design. Later eudicots moved to tricolpate pollen (three furrows), which may improve germination performance under varied conditions—a small tweak with big evolutionary echoes.
Primitive wood and plumbing: Without high‑throughput vessels (or with early, ladder‑like versions), water transport was respectable rather than flashy. That likely limited height and drought tolerance but didn’t matter in rainforests and ponds. When more efficient vessels evolved and diversified, angiosperms stormed drier, taller, tougher niches.
Amborellales: 1 species. To see Amborella, you go to New Caledonia, acquire a guide with a good hat, and tread carefully.
Nymphaeales: ~90 species. Visit almost any temperate or tropical pond and you’re likely meeting members of Nymphaeaceae or Cabombaceae. Botanical gardens love them; they do photogenic very well.
Austrobaileyales: ~100 species. Schisandra and Illicium turn up in Asian and North American gardens and forests; Austrobaileya clings to Australian rainforests; Trimeniaceae loiter discretely in the Asia‑Pacific.
Fossils give us hard anchors—this structure existed by this date—but early angiosperms were often small, soft, and not in a hurry to fossilize. Famous early angiosperm fossils (Archaefructus and friends) sketch possibilities but don’t neatly slot into the ANA picture. Molecular clocks convert genetic differences into time, which is marvelous until you realize different genes tick differently. Put together, they converge on the Early Cretaceous origin and early splits of the ANA grade, while leaving wiggle room that keeps paleobotanists cheerfully employed.
Without these lineages, we would struggle to reconstruct the architecture of the first flowers, the timing and impact of the angiosperm‑wide genome duplication, the transition from gymnosperm‑style wood to vessel‑bearing plumbing, and the early ecological experiments that set the stage for the later angiosperm explosion. They’re disproportionately informative for being, in total, fewer than two hundred species in a world of 300,000+ flowering plants.
The angiosperm story does not begin with exuberant daisies or baroque orchids. It begins with an unassuming shrub in New Caledonia that declined to invent vessels, with water‑lilies that made a living by lounging, and with woody aromatics that discovered scent as both shield and invitation. From these quiet beginnings came the green riot that feeds, clothes, and generally indulges us.
Open questions remain, and they’re good ones: Precisely how were the first flowers built, developmentally speaking? Which came first—certain floral traits or the pollinators that like them? And is the root of the angiosperm tree exactly where we think it is, or will the next tranche of data slide it a few twigs to one side?
For now, the ANA grade remains a gentle marvel: the living echoes of the first flowers on Earth, waving from rainforests and ponds as if to say, We started this. Do try to keep up.