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LECTURE 10 – Basal Angiosperms
NOTE: FLORAL FORMULAE LISTED HERE AND IN LATER LECTURES
ARE TEXT ONLY, AND THEREFOR INCOMPLETE
Overview –
• What is a “basal” angiosperm ?
• What are the basal angiosperms !?
• Details on 5 families that span the basal diversity
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Amborellaceae
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Nymphaeaceae
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Illiciaceae
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Magnoliaceae
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Piperaceae
What is a “basal” angiosperm?
Nowadays we restrict use of the words “primitive” & “derived” to individual
characters, not to taxa.
• “Basal” clades à those that branch off closer to the base of a tree.
The word should not be taken to mean “more primitive” because à
Ø Any living angiosperm is a mixture of apomorphies + plesiomorphies
Ø Any living angiosperm species ultimately traces back to the same point in
time, the root node … so Amborella has evolved for as long as, say, the
lineage that gave rise to Nicotiana
• “Basal” groups (including “living fossils”) are not more “primitive” but typically have
very different combinations of primitive + derived characters than, say, all of the
taxa in the Eudicots
• No such thing as “a basal-most angiosperm”
-- Each basal group (eg Amborella) must have a sister-group (eg “the rest of the
Angiosperms”) that also branches off at the base
Ø So eg Amborella is not more “primitive” than eg a member of a more
“terminal” group like Solanaceae
Ø But looking at a variety of basal groups gives us a better chance to figure
out what the most primitive angiosperms did actually look like!
What are the basal angiosperms (& how are they interrelated)?
Fair to say that we have learned more about basal angiosperm relationships in the
last year than in the preceding few decades.
In particular 5 key molecular studies largely agree on the
branching order of the basal angiosperms:
Ø Mathews & Donoghue 1999 Science 286: 947—950
Ø Soltis et al. 1999 Nature 402: 402 – 403
Ø Qiu et al. 1999 Nature 402: 403 – 407
Ø Parkinson et al. (in press) Curr Biology
Ø Graham & Olmstead (in press) Am J Botany
Consecutive splits up the angiosperm tree are as follows
(1)
Amborella vs. the rest of the angiosperms
(2)
Nymphaeaceae (the “water lilies”) vs. the remainder
(3)
(Illiciaceae + Schisandraceae + Austrobaileyaceae + Trimeniaceae)
vs. the remainder
• The next steps up the ladder are still not so well resolved
• Likely comprise at least the following additional basal angiosperm taxa
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
à
Magnoliales
(6 families incl. Magnoliaceae)
Laurales
(7 families incl. Lauraceae)
Piperales
(4 families incl. Piperaceae, Aristolochiaceae)
Winteraceae + Canellaceae
Chloranthaceae
Hydnoraceae…
(mentioned in LECTURE 9)
Rafflesiaceae…
(mentioned in LECTURE 9)
Ceratophyllum
Monocots …
(LECTURES 11 – 13)
Eudicots …
(LECTURES 15 – 22)
• This course, like most plant systematics courses, focuses on clades 12 and 13
• BUT should be emphasized that much of the evolutionary diversity of the flowering
plants resides in clades (1) through (11), although numerically these have far
fewer living species than the monocots & eudicots
So while today’s class only scratches at the surface of basal angiosperm diversity,
we will look in detail at a few families from these basal clades
Note: The Judd et al. book misplaces Illiciales. It is not closely related to
Winteraceae (this was based on older morphological study: molecular evidence
strongly contradicts that relationship)
Amborellaceae Pichon
Single species: Amborella trichopoda Baill.
Endemic to New Caledonia; humid forests
Long recognized as an “oddball” in Laurales but …
Now recognized as likely sister-group of the rest of the living angiosperms
• A vessel-less angiosperm; Ethereal oil cells absent; Sessile stigma
• Carpel closure by “secretion-occlusion” rather than tissue fusion
• Spirally arranged floral parts (except carpels are in a whorl)
Habit:
Leaves:
Weedy evergreen shrub
Alternate (spiral to distychous), petiolate, simple blades, margin
undulate or dentate, no stipules
Floral:
Dioecious; Cymose small panicles of male or female flowers
Pollination
Presumably insect-pollinated
Fruit dispersal Animal-dispersed ?
Staminate flowers:
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-5 - 8- , 10-14, 0
Pistillate flowers:
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-5 - 8-, 0
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•,
5-8
aggregate: fleshy stipitate drupes
Each flower has bracteoles that grade into tepals
Single ovule per carpel; Placentation marginal
Apocarpous; Superior ovaries;
Inaperturate pollen (to ~1-aperturate)
Nymphaeaceae Salisbury
(Water lily family)
8 genera, 70 spp. (incl. Nymphaea, Cabomba, Nuphar)
Widespread; Trop. to cold Temp . Rivers, ponds, lakes, wetlands
à Long viewed as possible link to the monocots (a view that no longer holds water),
Now viewed as near or at the basal split in angiosperms
• Ovary position very variable across family !!
• Carpel closure by secretion-occlusion & partial tissue fusion
Habit:
Leaves:
Floral:
Pollination
Fruit dispersal
Floral formula
Herbaceous, rhizomatous aquatics. Veg. propagation
Alternate, opposite (or even whorled); long-petiolate; variable
blade shape (can be heterophyllous); blade submersed, floating
or emergent; stipules +/Bisexual flowers; Inflorescence = solitary flower
Insect-pollinated (beetles, flies, bees). Various rewards, including
heat (thermogenic flowers); some are “trap” flowers
Water-dispersed
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-4 -12- , 0-infinity, 3-infinity, 1-infinity
Usu. berry, or aggregate of nuts, or irreg. dehiscent capsule
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Slime producing hairs
Stigma = radiating zones on disc or inner cup-shaped surface of ovary
Flowers with long pedicel, usu. floating or raised above water; Protogynous
Seeds usu. operculate (= open by a cap)
Tepals (+/- showy) intergrade with stamens (sometimes there are staminodes)
1 to numerous ovules per carpel; Parietal/ laminar placentation
Apocarpous or syncarpous carpels, inferior to superior ovary !!
Pollen monosulcate or inaperturate
Economic importance: Ornamentals
Illiciaceae A C Smith
(Star Anise family)
Illicium L. is sole genus, 37 spp.
SE Asia, SE US, Mexico, Carribean. Moist forests
à Trad. viewed as in Magnolilales, perhaps near Winteraceae,
Now recognised as much more basal (w/ Schisandraceae, Austrobaileyaceae,
Trimeniaceae)
• Vessels present
• Tricolpate pollen – Not homologous with that in Eudicots !!
• Carpel closure by secretion & partial tissue fusion
Habit:
Leaves:
Floral:
Pollination
Fruit dispersal
Floral formula
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Trees or shrubs. Veg. propagation by rhizomes
Alternate (often clustered at shoot apex), petiolate;
blade simple and entire, no stipules
Bisexual flowers; Thermogenic !; Inflorescence = 1-3 fls, axillary
Insect-pollinated (flies); Self-incompatible
Explosive dispersal
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-7 – infinite- , 7 - infinite, 7 - infinite
Follicles
Outer tepals sepal-like, inner tepals can be minute
Stigma extends down style (adaxial side)
1 ovule per carpel; More or less basal placentation
Carpels in a whorl & free but laterally compressed; Superior ovaries
Fruit a starlike aggregate of 1-seeded follicles
Pollen tricolporate
Economic importance: Anise (spice) from I. verum; Medicinal; Fumigant;
Ornamental shrubs
Magnoliaceae A. L. de Jussieu
(Magnolia family)
2 genera, 220 spp. (Magnolia, Liriodendron)
Trop to warm temp (esp. N). Moist forests
20th century view as a very “primitive angiosperm”: Tepals, stamens and carpels all
spirally arranged
• Vessels present; Ethereal oils produced
• Spirally arranged floral parts
• Carpel closure by “secretion” & partial tissue fusion
Habit:
Leaves:
Floral:
Pollination
Fruit dispersal
Floral formula
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Trees or shrubs
Alternate (spiral to 2-ranked), petiolate; simple to lobed blade;
stipules present
Usu. bisexual flowers; Inflorescence = single terminal flower
Insect-pollinated (beetles, bees); Self-incompatibility known
Bird- or wind-dispersed
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-6 - infinity- , infinity, infinity
Follicles, samaras
Stigma usu. extends down style on adaxial surface
Flowers have elongate receptacle
Fruit usu. = aggregate of appressed follicles
Follicles split on abaxial surface, carpal midvein (cf. all other angiosperms)
Tepals distinct, usu. numerous (sometimes outer 3 = sepaloid)
2 (+) ovules per carpel; Parietal placentation
Superior ovary (usu. apocarpous)
Pollen monosulcate
Economic importance: Ornamentals, timber
Piperaceae C A Agardh
(Pepper family)
6 genera, c. 2020 spp. (incl. Peperomia – 1000 spp., Piper– 1000 spp)
Widespread; Trop to sub-Trop. Moist forests
à Trad. close to Magnoliales. This and recent concept of a “paleoherb” group (incl.
Saururaceae, Aristolochiaceae, Lactoridaceae) supported by DNA & morphology.
• Vessels present usu. with simple perforations
• Tiny inconspicuous flowers; Densely arranged on thick spike
• Carpel closure by complete tissue fusion
Habit:
Leaves:
Floral:
Pollination
Fruit dispersal
Floral formula
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Herbs (… to small trees); some are epiphytes
Alternate, petiolate (to petiolate sheathing), blade simple & entire,
stipules +/Bisexual, or unisexual flowers (plants then monoecious or
dioecious); Inflorescence = terminal or axillary, indeterm. spike
Probably insect-pollinated; Protogynous
Animal dispersed
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-0- , 1 - 10, 1 – 4
Drupe
Ethereal oils present
No perianth… but each flower has a triangular to peltate bract
Stigma capitate, lobed or brush-like
1-4 syncarpous carpels but 1-locule and single ovule; Superior ovaries
Basal placentation
Fruit a drupe
Pollen monosulcate or inaperturate
Economic importance: Spice (black & white pepper); Stimulant (“betel pepper”);
Medicinal; Foliage ornamentals (Peperomia)