Flower Morphology and Development

Flower Morphology and Flower Morphology and DevelopmentDevelopment

OverviewOverviewFloral MorphologyFloral Morphology

Flower PartsFlower Parts

Flower DevelopmentFlower Development

Floral EvolutionFloral EvolutionPaleoherbsPaleoherbs

Evolved in dry upland Evolved in dry upland habitats (habitats (AxelrodAxelrod).).Supported by Supported by paleopaleobotanists.botanists.

Woody magnoliasWoody magnoliasTropical shrubs.Tropical shrubs.Not diversified in Not diversified in contemporary florascontemporary florasSupported by Supported by molecular analyses of molecular analyses of living living taxataxa (Doyle and (Doyle and DonoghueDonoghue). ).

Floral EvolutionFloral Evolution

Evolutionary TrendsEvolutionary Trends

Ovules enclosedOvules enclosedOvules exposedOvules exposed

DerivedDerived(advanced)(advanced)

AncestralAncestral(primitive)(primitive)

Few (invariable)Few (invariable)flower partsflower parts

Multiple (variable) Multiple (variable) flower partsflower parts

Bilateral Bilateral symmetrysymmetryZygomorphicZygomorphic

Radial symmetryRadial symmetryActinomorphicActinomorphic

Ovary inferiorOvary inferiorOvary superiorOvary superior

Parts within a Parts within a whorl fusedwhorl fused

Parts within a Parts within a whorl separatewhorl separate

A

B

C

D

EPhylogenetic Tree(cladogram)

Evolution of AngiospermsEvolution of AngiospermsBryophyte fossils back to 425 Bryophyte fossils back to 425 MYBP.MYBP.First Angiosperm fossil records First Angiosperm fossil records 130 MYBP during the Jurassic.130 MYBP during the Jurassic.

Perhaps as early as 250 MYBP Perhaps as early as 250 MYBP based on chemical evidence.based on chemical evidence.

Began to spread and become Began to spread and become dominant during the dominant during the CretaceousCretaceous

Association with animals.Association with animals.250,000 species in 350 250,000 species in 350 families.families.Molecular and morphological Molecular and morphological characters indicate characters indicate monophyletic origin.monophyletic origin.Initial origin and spread in Initial origin and spread in Gondwanaland. Gondwanaland.

500 MYBP

Floral MorphologyFloral MorphologyThe concept of floral The concept of floral syndromes.syndromes.

MorphologyMorphologyColorColorScentScentNectar compositionNectar compositionPhenologyPhenology

Floral MorphologyFloral Morphology

The concept of specialization.The concept of specialization.Phenotypic attributes that Phenotypic attributes that promote the association with a promote the association with a single pollinator species, or a single pollinator species, or a guild of pollinators.guild of pollinators.PhylogeneticPhylogenetic trends.trends.

PolyphilyPolyphily (generalists)(generalists)OligophilyOligophily (specialists)(specialists)Example: Example: RanunculaceaeRanunculaceae(buttercup family)(buttercup family)

Floral SpecializationFloral SpecializationTrends towards Trends towards specializationspecialization::

SymmetrySymmetryRadial (Radial (actinomorphicactinomorphic))

Cup, bell, or brushCup, bell, or brush--shaped flowersshaped flowersBilateral (Bilateral (zygomorphiczygomorphic))

Peas, orchids, mints, irises, etc.Peas, orchids, mints, irises, etc.

PerianthPerianthOpenOpenTubularTubular

RewardReward--access mechanismsaccess mechanismsReward typeReward type

Floral tissue/pollenFloral tissue/pollenNectarNectarNonNon--nectar reward typesnectar reward types


PerianthPerianth colorcolorTriTri--chromatic vision of insects.chromatic vision of insects.

Shifted to UV, red “blind.”Shifted to UV, red “blind.”

Color by pollinator.Color by pollinator.Bees Bees –– yellow, blue.yellow, blue.Butterflies Butterflies –– yellow, blue.yellow, blue.Moths Moths –– white, yellow.white, yellow.Hummingbirds Hummingbirds –– red, yellow.red, yellow.


PerianthPerianth color color patternspatterns

Bee pollinationBee pollinationTargetsTargetsNectar guides.Nectar guides.

Pollination SyndromesPollination Syndromes

ScentScentBees use scent profiles to locate flowersBees use scent profiles to locate flowersMoth pollination Moth pollination –– often sweet smellingoften sweet smellingFly/beetle pollination Fly/beetle pollination –– rancid scentsrancid scents

NectarNectarSugar concentration (10 Sugar concentration (10 –– 74%)74%)Sugar composition (Baker and Baker, Sugar composition (Baker and Baker, 1979)1979)

Sucrose/Sucrose/HexoseHexose (glucose, fructose) ratio.(glucose, fructose) ratio.Amino acids.Amino acids.

PhenologyPhenologyFlower longevityFlower longevityNightNight--blooming speciesblooming species

Floral Syndromes Floral Syndromes –– Current ViewsCurrent Views

Pollinator specialization Pollinator specialization -- coevolutioncoevolutionFaegri and van der Pijl, 1979

Syndromes are “generalized”Syndromes are “generalized”WaserWaser et al., 1996et al., 1996

Challenge to the pollinator effectiveness Challenge to the pollinator effectiveness hypothesis.hypothesis.

NonNon--coevolved pollinators (bees) deposit more pollen coevolved pollinators (bees) deposit more pollen in in IpomopsisIpomopsis Mayfield et al., 2001Mayfield et al., 2001FensterFenster et al. 2004.et al. 2004.

Floral Syndromes Floral Syndromes –– Current ViewsCurrent Views

Hypotheses for the evolution of Hypotheses for the evolution of syndromessyndromes

Pollinator effectivenessPollinator effectivenessInducing pollinator constancyInducing pollinator constancyExcluding unwanted pollinatorsExcluding unwanted pollinators

Current ResearchCurrent Research

Tim Holtsford labhttp://www.biosci.missouri.edu/holtsford/nicotiana/

Scott Hodges labhttp://www.lifesci.ucsb.edu/eemb/faculty/hodges/research.html

BibliographyBibliography

Baker, H. G., and I. Baker. 1979. Sugar ratios in nectars. Phytochemical Bulletin 12:43-45.Faegri, K., and L. van der Pijl. 1979. The Principles of Pollination Ecology. Pergamon, Oxford.Hodges, S. A., and M. L. Arnold. 1994. Columbines: a geographically widespread species flock. Proc-Natl-Acad-Sci-U-S-A. 91:5129-5132.Mayfield, M. M., N. M. Waser, and M. V. Price. 2001. Exploring the 'most effective pollinator principle' with complex flowers: Bumblebees and Ipomopsis aggregata. Annals of Botany 88:591-596.Waser, N. M., L. Chittka, M. V. Price, N. M. Williams, and J. Ollerton. 1996. Generalization in pollination systems, and why it matters.Ecology 77:1043-1060.

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Flower Morphology and Development