1. Origins of Angiosperms
Spring 2010

2. Outline Origin of the angiosperms Characters of angiosperms
Brief history of angiosperm classification
Major groups of angiosperms
ANITA grade

3. Origin of the Angiosperms

4. ? Divergence estimated at ca. 325 mybp Conifers Ginkgo Gnetophytes
Cycads
Ginkgo
Conifers
Gnetophytes
Angiosperms ?
Progymnosperms
(“seed ferns”)
Divergence estimated at
ca. 325 mybp

5. Geologic Time

6. Timing of Angiosperm Divergences
The timing of the origin of the angiosperms still is uncertain, but most would agree on a Triassic or Jurassic initial divergence, although there is no unequivocal fossil evidence
A demonstrable “burst” of phylogenetic radiation is found in the fossil record beginning in the mid- to-late Cretaceous, mybp

7. Figure 7.16 from the text

8. Origin of the Angiosperms
pollen grains from ca. 140 mya (early Cretaceous) but already major radiation!
earliest flowers 130 mya
likely no extant group of seed plants is very closely related to the angiosperms!

9. Origin of Angiosperms Cycad-like plants: Bennettitales?
large, flowerlike strobili:
pollen-producing organs surrounding an axis bearing naked ovules/seeds

10. Origin of Angiosperms Modification of a “seed fern” such as Caytonia?
fossil: ovule

11. Origin of Angiosperms Archaefructus ca. 130 mya
ancestral flowering plant or
extinct off-shoot of an extinct lineage?
aquatic plant (dissected leaves)
elongate reproductive axes:
-paired stamens below
-several-seeded carpels above

12. Characters of Angiosperms

13. Reduced male and female gametophytes!
Angiosperms (Flowering Plants)
“Dicotyledons”
Magnoliids
Eudicots
Monocots
-- likely evolved WITHIN angiosperms
Reduced male and female gametophytes!
ALSO:
-- nonmotile sperm!
(evolved independently in certain non flowering taxa)

14. What makes a plant an angiosperm?
Flower (usually with perianth)
Carpels with a stigmatic surface for pollen germination; ovules enclosed within carpels; fruit
Ovules with two integuments
Reduced female gametophyte, usually 8 nuclei in 7 cells – no archegonium
Double fertilization with the production of 3N endosperm
Stamens with two pairs of lateral pollen sacs (microsporangia)
Xylem – most with vessels (evolved within angiosperms)
Phloem – sieve tube members with 1 or more companion cells derived from the same mother cell

15. Figure 4.16 from the text
Flower

16. Spiral undifferentiated
perianth parts = tepals
(plesiomorphic)

17. Differentiated sepals and
petals (each in whorls)
(apomorphic)

18. Laminar stamens
in basal angiosperms
paired pollen
sacs
connective
microsporangium
filament

19. Early carpel with
stigmatic crest…
Figure 4.19 from the text
Figure 4.20 from the text
…to the derived carpel
with a style and an
apical stigma.

20. Female gametophyte in angiosperms
-no waiting time as in gymnosperms!
-note 2 integuments (bitegmic; some angiosperm lineages
have lost one integument)
-gymnosperms have
only 1 integument
(unitegmic)
mature ovule
ovule

21. Seed development in angiosperms
-no waiting time as in gymnosperms!
double fertilization
seed

22. flower fruit Avocado (Persea, Lauraceae) exocarp mesocarp endocarp
seed

23. Vessels in Angiosperms
are the water (solute) conducting cells of the
xylem in most angiosperms
ends of cells have openings (perforation
plate), cells shorter and wider
more efficient, faster rate of flow but more
susceptible to air bubbles (embolisms) than
tracheids are
may have arisen independently in two or more
angiosperm lineages but may have had a
single origin

24. Origin of vessels from tracheids
Figure 4.32 from the text

25. Angiosperm phloem sieve tube members + companion cells
stm = specialized sugar-conducting
cells of the phloem of angiosperms;
lack a nucleus at functional maturity
cc = parenchyma cells associated
with stm
-function to load/unload sugars into stm cavity
-derived from the same mother
cell as its stm
stm

26. Brief history of angiosperm classification

27. Alternative ways of thinking about early angiosperm characters…
“Old” School (German) - Engler
- “Simple is primitive” (Few floral parts)
- Ancestors are conifers
- Pollination by wind
- Modern relicts = “Amentiferae” (catkins)
“New” School (American) – Bessey
- “Flowers with many parts are primitive”
- Ancestors are Cycad-like plants
- Pollination by primitive insects
- Modern relicts = Magnolias and allies

28. Heinrich Gustav Adolph Engler (1844-1930)
German Botanist at Berlin Botanical Garden -Was the primary European in interpreting the grouping of major angiosperm assemblages -“Few simple flower parts primitive” -Small, unisexual flowers primitive

29. Englerian ‘Primitive Taxa’
Juglans sp.
Quercus sp.
“Amentiferae”
Betula sp.

30. Charles Edwin Bessey (1845-1915)
-Botanist at Iowa State University from (left in 1884 to teach in Nebraska) -Was a “major player” in interpreting and understanding angiosperm evolution -“Many flower parts primitive”
Bessey Hall
Iowa State University

31. Bessey’s “Cactus” Placed plant groups with many floral
(1915)
Placed plant groups
with many floral
parts in a basal
position as the
‘ancestral’ forms.
Outlined ‘dicta’ for
the construction of
phylogenies using the
evolutionary trends in
character changes.
Polypetalous flowers,
insect pollination,
cycad-like ancestors

32. Besseyan ‘Primitive Taxa’
Nymphaeaceae
Magnoliaceae

33. Figure 7.16 from the text

34. Major Groups of Angiosperms
Basal Angiosperms (ANITA grade)
- Amborellaceae
- Nympheaceae
- Illiciaceae
Magnoliid Complex (incl. “paleoherbs”)
- Magnoliales
- Piperales
- Winterales
MONOCOTS
EUDICOTS (tricolpates)

35. Major Groups of Eudicots
Basal Tricolpates
- Ranunculales and allied families
Caryophyllales & Saxifragales
Rosid Clade
- Basal Rosids
- Eurosids I (Fabids)
- Eurosids II (Malvids)
Asterid Clade
- Basal Asterids
- Euasterids I (Lamiids)
- Euasterids II (Campanulids)

36. ANITA grade Amborella (Amborellales) Nymphaea (Nymphaeales)
Illicium (Austrobaileyales)
Trimenia (Austrobaileyales)
Austrobaileya (Austrobaileyales)

37. Figure 9.1 from the text > 125 mybp > 140 mybp ANITA grade
Grade = a polyphyletic (or
paraphyletic) group whose
members share a similar
level of morphological or
physiological complexity.
> 140 mybp

38. Major Angiosperm Clades
Amborellaceae
Nymphaeales
Austrobaileyales
MAGNOLIID
COMPLEX
MONOCOTS
EUDICOTS
[TRICOLPATES]
“BASAL FAMILIES”
Soltis et al. 2000,
APG II 2002,
Judd et al. 2002

39. Basal Angiosperms: Amborellaceae
New Caledonia
Understory shrub; plants dioecious
1 species (monotypic): Amborella trichopoda
Leaves simple, evergreen
Flowers small, unisexual: ♀ apocarpous, with stigmatic crests; ♂ with laminar stamens
Significant features: Most basal of all flowering plants; no vessels in wood
Special uses: (none)

40. Basal Angiosperms: Amborellaceae (Amborella Family)
Amborella trichopoda

41. Basal Angiosperms: Nymphaeaceae (Water Lily Family)
Widespread, tropics to temperate regions
Aquatic rhizomatous herbs, sap milky
70 species; 8 genera
Flowers: many parts; laminar stamens; “floating”; colorful perianth; “beetle” syndrome
Special uses: ornamentals; sacred lotus
Required taxa: Nymphaea (water lily)

42. Basal Angiosperms: Nymphaeaceae (Water-lily Family)
numerous petals, stamens, carpels
laminar stamens
pollen monosulcate
stigma discoid, radiating
berry-like fruit, dehiscent
perisperm
usually lack vessels (or have tracheid-like vessels)

43. Nymphaea odorata – Water Lily

44. Nymphaea tuberosa Water Lily

45. Nuphar Water Lily

46. Victoria amazonica – Giant Water Lily

47. Basal Angiosperms: Illiciaceae (Star Anise Family)
SE Asia, SE USA and Caribbean
Trees and shrubs
1 genus, Illicium; ca. 40 species
Flowers: many floral parts/tepals; 1 ovule/carpel
Special uses: star anise (spice)
Required taxa: (none)

48. Illicium – Star Anise
Illicium parviflorum
Illicium floridanum

49. As we venture through the various major groups of angiosperms…
Identify the plesiomorphic characteristics associated with particular groups and note their apomorphies (if any) as well.
Try to associate “syndromes” of characteristics with each group (make note of special characters occurring together).
One good way to study is to write keys to the groups we cover in any given unit.
Names of groups are important! Learn to spell and say them!
Ask questions!!