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paper!paper!1Source: Basic Formatting!

Evolution of AngiospermsEvolution of Angiosperms

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““The rapid development The rapid development as far as we can judge of as far as we can judge of

all the higher plants all the higher plants within recent geological within recent geological times is an abominable times is an abominable

mystery.”mystery.”

-- letter from C. Darwin to J. Hooker -- letter from C. Darwin to J. Hooker 2 July 1879

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Putative Angiosperm Putative Angiosperm AncestorsAncestors

Bennettiales?Bennettiales? Flowerlike, bisexual strobiliFlowerlike, bisexual strobili

Separate ovulate and pollen-bearing Separate ovulate and pollen-bearing sporophyllssporophylls

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Putative Angiosperm Putative Angiosperm AncestorsAncestors Conflicting hypothesesConflicting hypotheses

Remains an “abominable mystery”Remains an “abominable mystery”

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Unique characteristics of Unique characteristics of AngiospermsAngiosperms

FlowersFlowers Seeds enclosed in carpelSeeds enclosed in carpel Double fertilization Double fertilization endosperm endosperm Much reduced microgametophyte Much reduced microgametophyte Reduced megagametophyte (7 cells; 8 Reduced megagametophyte (7 cells; 8

nuclei)nuclei) Stamens with paired pollen sacsStamens with paired pollen sacs Sieve-tube elements & companion cellsSieve-tube elements & companion cells

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Earliest Angiosperm Earliest Angiosperm FossilsFossils

Pollen grains from 135 myaPollen grains from 135 mya Whole plant – Whole plant – ArchaefructusArchaefructus

~ 125 mya~ 125 mya Semi-aquaticSemi-aquatic

Middle Cretaceous – many Middle Cretaceous – many lineages presentlineages present

End Cretaceous – End Cretaceous – angiosperms dominantangiosperms dominant

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Phylogenetic Phylogenetic RelationshipsRelationships

Monocots and Monocots and EudicotsEudicots – 97% of – 97% of angiospermsangiosperms Monocots -- monophyleticMonocots -- monophyletic

o Synapomorphy – single cotyledonSynapomorphy – single cotyledon Eudicots – monophyleticEudicots – monophyletic

o Synapomorphy – triaperturate pollenSynapomorphy – triaperturate pollen

Remainder – multiple different evolutionary Remainder – multiple different evolutionary lineslines Some arose before monocot/dicot splitSome arose before monocot/dicot split

o Monoaperturate pollen Monoaperturate pollen MagnoliidsMagnoliids

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Major Angiosperm Major Angiosperm GroupsGroups

Basal AngiospermsBasal Angiosperms MesangiospermsMesangiosperms

MagnoliidsMagnoliids MonocotsMonocots Basal EudicotsBasal Eudicots EudicotsEudicots

o RosidsRosidso AsteridsAsterids

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Groups of AngiospermsGroups of Angiosperms

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Basal AngiospermsBasal Angiosperms ANITA grade ANITA grade

Amborella (shrub from New Caledonia) (shrub from New Caledonia) Nymphaeales (water lilies and some (water lilies and some

other aquatic plants) other aquatic plants) Austrobaileyales (woody aromatic (woody aromatic

plants including star anise). plants including star anise). ANITA stands for the genera ANITA stands for the genera

AmborellaAmborella, , NymphaeaNymphaea, , IlliciumIllicium, , TrimeniaTrimenia and and AustrobaileyaAustrobaileya..

Sister to all other angiospermsSister to all other angiosperms11

Amborella trichopodaAmborella trichopoda

DioeciousDioecious UndifferentiaUndifferentia

ted stamensted stamens Drupes Drupes No vesselsNo vessels Embryo sac – Embryo sac –

8 celled and 9 8 celled and 9 nucleatenucleate

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The Rest of ANITAThe Rest of ANITA Nymphales – water liliesNymphales – water lilies Austrobaileya scandensAustrobaileya scandens

13Plantsystematics.org

MagnoliidsMagnoliids Numerous, spirally arranged floral Numerous, spirally arranged floral

partsparts Magnoliales Magnoliales (Magnolia),(Magnolia), Laurales Laurales

(Calycanthus),(Calycanthus), Piperales ( Piperales (Piper Piper and and AristolochiaAristolochia), Canellales), Canellales

Many AustralasianMany Australasian Essential Oils – nutmeg, pepper & Essential Oils – nutmeg, pepper &

bay leavesbay leaves

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MonocotsMonocots

Monoaperturate pollenMonoaperturate pollen 3-merous floral parts3-merous floral parts

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EudicotsEudicots Tricolpate pollenTricolpate pollen 4- and 5-merous floral parts4- and 5-merous floral parts

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Highly Highly Simplified Simplified AngiosperAngiosper

m m PhylogenyPhylogeny

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Major Major Groups of Groups of AngiosperAngiosper

msms Rosids Rosids

2 integuments2 integuments Nucellus with Nucellus with 2 2

layers of cellslayers of cells AsteridsAsterids

Single ingegumentSingle ingegument Nucellus with 1 Nucellus with 1

layer of cellslayer of cells

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Earliest AngiospermsEarliest Angiosperms Flowers lacking a perianthFlowers lacking a perianth 125 mya125 mya Leefructus Leefructus ArcharfructusArcharfructus

Resemble Resemble

AAmborellamborella

not not MagnoliaMagnolia

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Evolution of the FlowerEvolution of the Flower

Perianth – no distinct sepals and petalsPerianth – no distinct sepals and petals Some petals derived from sepalsSome petals derived from sepals Sepals derived from leavesSepals derived from leaves

Other petals apparently derives from Other petals apparently derives from stamensstamens

Sepals – same number vascular strands as Sepals – same number vascular strands as leavesleaves

Stamens – 1 vascular strandStamens – 1 vascular strand Petals – 1 vascular strandPetals – 1 vascular strand

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Evolution of the FlowerEvolution of the Flower Stamens – diverse structure and Stamens – diverse structure and

functionfunction Woody magnoliids – broad, colored and Woody magnoliids – broad, colored and

scentedscented High degree of differentiationHigh degree of differentiation

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Evolution of the FlowerEvolution of the Flower Unspecialized carpelsUnspecialized carpels

Extinct angiosperms – leaflike carpelsExtinct angiosperms – leaflike carpels Most extant angiosperms – Most extant angiosperms –

differentiated carpelsdifferentiated carpels Variation in placentationVariation in placentation

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Major Evolutionary Major Evolutionary TrendsTrends

Different pollination vectorsDifferent pollination vectors Bisexual/ unisexual flowersBisexual/ unisexual flowers Differentiated perianthDifferentiated perianth Specialized pollinators developSpecialized pollinators develop Fruit dispersal vectorsFruit dispersal vectors

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Generalized Evolutionary Generalized Evolutionary TrendsTrends

1.1. Flowers with indefinite merosity Flowers with indefinite merosity definite merositydefinite merosity

2.2. Floral axis shortened; floral parts Floral axis shortened; floral parts often fusedoften fused

3.3. Ovary inferior; differentiated Ovary inferior; differentiated perianthperianth

4.4. Actinomorphic symmetry Actinomorphic symmetry zygomorphiczygomorphic

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Floral Floral DiversityDiversity

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Specialized FamiliesSpecialized Families

Asteraceae and Orchidaceae – 2 Asteraceae and Orchidaceae – 2 largest familieslargest families

Among the most specializedAmong the most specialized One monocot – one eudicotOne monocot – one eudicot

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AsteraceaeAsteraceae

Disk Flowers & Ray FlowersDisk Flowers & Ray Flowers Any combination thereof!Any combination thereof!

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OrchidaceaOrchidaceaee

Highly Highly specialized specialized flowersflowers

Often intricate Often intricate pollinator pollinator relationshipsrelationships

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PollinatorsPollinators Primative -- WindPrimative -- Wind

Indistinct & ineffectiveIndistinct & ineffective Flowers much reducedFlowers much reduced Copious amounts of pollenCopious amounts of pollen

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Animals Agents of Floral Animals Agents of Floral EvolutionEvolution

Plants can’t move around (DuH!) – Plants can’t move around (DuH!) – depend on “animals”depend on “animals” Co-evolution Co-evolution Perfect flowers – each visit more Perfect flowers – each visit more

efficient!efficient!

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Beetle PollinatedBeetle Pollinated Flowers openFlowers open Dull coloredDull colored Strong (usually) fruity odorStrong (usually) fruity odor Floral parts thickFloral parts thick

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Fly pollinatedFly pollinated Carrion (or fruity) smellCarrion (or fruity) smell Reddish to purple-brownReddish to purple-brown No nectar guidesNo nectar guides

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Bee pollinatedBee pollinated

Flowers openFlowers open Colored but not redColored but not red Sweet odorSweet odor Nectar guidesNectar guides

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Bee Pollination: Bee Pollination: milkweed leg milkweed leg traptrap

Bee Pollination: Bee Pollination: milkweed leg milkweed leg traptrap

Pollen sacs [pollinium]

Butterfly PollinatedButterfly Pollinated

Flowers produce nectarFlowers produce nectar Various colors – redsVarious colors – reds Sweet odorSweet odor Nectar guidesNectar guides Often landing platformsOften landing platforms

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Nocturnal Moth Nocturnal Moth PollinationPollination

Open at nightOpen at night Usually white (or light)Usually white (or light) Strong/ sweet odorStrong/ sweet odor Lots of nectarLots of nectar

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Deception PollinationDeception Pollination

False food rewardFalse food reward Sweet smellSweet smell NectarNectar Mimic food-rewarding flowersMimic food-rewarding flowers

Sexual deceptionSexual deception Pseudo-copulation Pseudo-copulation Prominent in orchidsProminent in orchids

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Bat pollinatedBat pollinated

Flowers open at nightFlowers open at night WhiteWhite Strongly scentedStrongly scented Lots of pollenLots of pollen

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Bird PollinatedBird Pollinated

Copious, thin nectarCopious, thin nectar Little odorLittle odor Colorful – often redColorful – often red Tubular Tubular

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Important PigmentsImportant Pigments Small number of pigmentsSmall number of pigments

CaretonoidsCaretonoids Flavinoids -- Block UVFlavinoids -- Block UV

o Anthocyanins Anthocyanins o Water solubleWater solubleo pH determines colorpH determines coloro Colors can change post pollinationColors can change post pollination

o FlavonolsFlavonolso Colorless – white/ivory pigmentsColorless – white/ivory pigments

BetalainsBetalainso Only in CaryophyllidsOnly in Caryophyllids

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Marsh MarigoldMarsh Marigold

Outer yellow – UV absorbing Outer yellow – UV absorbing carotenoidscarotenoids

Inner yellow – UV reflective flavinoid Inner yellow – UV reflective flavinoid calchonecalchone

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FruitsFruits Ripe ovary and associated structuresRipe ovary and associated structures Fruit dispersal fundamental aspect Fruit dispersal fundamental aspect

of radiationof radiation Parthenocarpic -- without Parthenocarpic -- without

fertilization and seed development fertilization and seed development (e.g., banana, pineapple, citrus …)(e.g., banana, pineapple, citrus …)

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Fruit TypesFruit Types

Simple FruitSimple Fruit One of more fused carpels from single flowerOne of more fused carpels from single flower

Aggregate FruitAggregate Fruit Individual carpels in a single flowerIndividual carpels in a single flower

Multiple FruitMultiple Fruit Derived from an inflorescence (e.g., many Derived from an inflorescence (e.g., many

flowers)flowers) Accessory FruitAccessory Fruit

Tissue not from ovaryTissue not from ovary

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Simple FruitsSimple Fruits Fleshy or Dry at maturityFleshy or Dry at maturity FleshyFleshy

Berries – 1 –many seeds; all parts fleshyBerries – 1 –many seeds; all parts fleshy Drupes – 1 seeded; fleshy mesocarp; stony Drupes – 1 seeded; fleshy mesocarp; stony

endocarpendocarp Pomes – compound inferior ovary – accessory Pomes – compound inferior ovary – accessory

fruitfruit DryDry

Dehiscent – multiple seedsDehiscent – multiple seedso Legume, silique, follicle, capsuleLegume, silique, follicle, capsule

Indehiscent – only one seedIndehiscent – only one seedo Achene, samara, cypselsAchene, samara, cypsels

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Fruit DispersalFruit Dispersal WindWind

Dandelions – cypselasDandelions – cypselas Maples – schizocarpMaples – schizocarp

WaterWater CoconutCoconut

AnimalsAnimals Ingestion Ingestion AdheringAdhering

Self-dispersalSelf-dispersal

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Biochemical EvolutionBiochemical Evolution

Secondary MetabolitesSecondary Metabolites Alkaloids – morphine, cocaine, caffeine, Alkaloids – morphine, cocaine, caffeine,

nicotinenicotine Terpenoids – taxol, rubber, cardiac Terpenoids – taxol, rubber, cardiac

glycosides, isopreneglycosides, isoprene Phenolics – flavonoids, tannins, lignins, Phenolics – flavonoids, tannins, lignins,

catechols, salicylic acidcatechols, salicylic acid Quinones – coqnzyme QQuinones – coqnzyme Q Raphids – Calcium oxalateRaphids – Calcium oxalate

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Secondary MetabolitesSecondary Metabolites

Protect against herbivoryProtect against herbivory Reduce palatabilityReduce palatability Total avoidanceTotal avoidance

Mustards – cabbage, horseradish, Mustards – cabbage, horseradish, mustardmustard Avoided by most herbivorous insectsAvoided by most herbivorous insects Attractants for others (e.g., cabbage Attractants for others (e.g., cabbage

butterfly)butterfly) Insects that do feed often brightly coloredInsects that do feed often brightly colored

They are also protected from predationThey are also protected from predation

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