Spring 2014 Outline Origin of the angiosperms Characters of angiosperms Brief history of angiosperm classification Major groups of angiosperms ANITA grade Origin of the Angiosperms Conifers ID: 742584
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Slide1
Origins of Angiosperms
Spring
2014Slide2
OutlineOrigin of the angiosperms
Characters of angiosperms
Brief history of angiosperm classification
Major groups of angiosperms
ANITA gradeSlide3
Origin of the AngiospermsSlide4
Conifers
Ginkgo
Cycads
Gnetophytes
Angiosperms
Divergence estimated at
ca. 325
mybp
Progymnosperms
(“seed ferns”)Slide5
Geologic TimeSlide6
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, 140 - 100 mybpSlide7
Figure 7.1Slide8
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!Slide9
Origin of Angiosperms
Cycad-like plants: Bennettitales?
large, flowerlike strobili:
pollen-producing organs surrounding an axis bearing naked ovules/seedsSlide10
Origin of Angiosperms
Modification of a “seed fern” such as
Caytonia
?
Caytonia
fossil: ovuleSlide11
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 aboveSlide12
Characters of AngiospermsSlide13
Fig. 6.1Slide14
What makes a plant an angiosperm?
Flower
(usually with perianth)
Carpels
with a stigmatic surface for
pollen tube
germination; ovules enclosed within carpels; fruit
Ovules with two integumentsReduced female gametophyte, usually 8 nuclei in 7 cells – no archegonium
Double fertilization with the production of 3N endospermStamens with two pairs of lateral pollen sacs (microsporangia);
pollen (male gametophyte) 3-nucleateXylem – most with vessels (evolved within angiosperms)
Phloem – sieve tube members with 1 or more
companion cells derived from the same mother cellSlide15
Flower
Figure 6.2Slide16
Spiral undifferentiated
perianth parts = tepals
(plesiomorphic)
Magnolia
MagnoliaSlide17
Differentiated sepals and
petals (each in whorls)
(apomorphic)
AbutilonSlide18
connective
microsporangium
filament
Laminar stamens
in basal
angiosperms
(
plesiomorphic
)
paired pollen
sacsSlide19
Early carpel with
stigmatic
crest
(
plesiomorphic
)…
…to the derived carpel
with a style and an
apical
stigma (
apomorphic
).
Figure 6.9 from the textSlide20
Female gametophyte in angiosperms
ovule
-no waiting time as in gymnosperms!
-note 2 integuments (bitegmic; some angiosperm lineages
have lost one integument)
-gymnosperms have
only 1 integument
(unitegmic)
mature ovuleSlide21
And it’s off
to the races!
Indirect
pollination
(due to presence
of carpels)Slide22
-no waiting time as in gymnosperms!
Seed development in angiosperms
seed
double fertilizationSlide23
Avocado
(
Persea
, Lauraceae)
seed
endocarp
mesocarp
exocarp
pericarp
Flower
fruitSlide24
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
Vessels in AngiospermsSlide25
Origin of vessels from tracheids
Figure 6.16B from the textSlide26
Angiosperm phloem
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
sieve tube members
+
companion cells
stmSlide27
Brief history of angiosperm classificationSlide28
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
Slide29
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 primitiveSlide30
Englerian ‘Primitive Taxa’
“Amentiferae”
Quercus sp.
Juglans sp.
Betula sp.
Slide31
Charles Edwin Bessey
(1845-1915)
-Botanist at Iowa State University
from 1869-1884 (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 UniversitySlide32
Bessey’s “Cactus”
(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 ancestorsSlide33
Besseyan ‘Primitive Taxa’
Nymphaeaceae
MagnoliaceaeSlide34
Figure 6.1 from the textSlide35
Major Groups of Angiosperms
Basal Angiosperms (ANITA grade)
-
Amborellaceae
-
Nympheaceae
-
Illiciaceae
Magnoliid Complex -
Magnoliales - Piperales
-
Winterales
MONOCOTSEUDICOTS (
tricolpates) Slide36
Major Groups of Eudicots
Basal
Eudicots
-
Ranunculales
and allied families
Caryophyllales
& Saxifragales
Rosid Clade - Fabids
- Malvids
Asterid Clade
- Basal Asterids
-
Lamiids - CampanulidsSlide37
ANITA gradeA
mborella
(Amborellales)
N
ymphaea
(Nymphaeales)
I
llicium (Austrobaileyales)Trimenia
(Austrobaileyales)Austrobaileya (Austrobaileyales)Slide38
ca. 125 mybp
Fig. 6.1
Grade
= a paraphyletic (or
Polyphyletic) group whose
members share a similar
level of morphological or
physiological complexity.
ANITA Grade
or “basal”
angiospermsSlide39
Major Angiosperm Clades
Amborellaceae
Nymphaeales
Austrobaileyales
MAGNOLIID
COMPLEX
MONOCOTS
EUDICOTS
[TRICOLPATES]
ANITA grade (basal groups)
Soltis et al. 2000,
APG II 2002,
Judd et al. 2002Slide40
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)Slide41
Basal Angiosperms:
Amborellaceae (Amborella Family)
Amborella trichopodaSlide42
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!!