Reproductive and life history strategies

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Reproductive and life history strategies

• Pollination syndromes
• Breeding systems
• Plant Gender and Mating systems
• Timing/frequency of reproduction
• Seed dispersal and dormancy

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Parts of a Flower
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Pollination syndromes
Pollination syndromes

• Statistical constructs particular floral traits
  tend to be over-represented among plant species
  that rely on particular pollinator species
• Our pollination lab will examine syndromes with
  morning glories

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Wind pollination
Pollination syndromes

• Scentless, rewardless, colorless/green, usually
  small pollen grains, often aerodynamically
  complex under magnification

Bird flowers

• Diurnal, often red, no scent, tubular, often
  pendent or horizontal, large quantities of dilute
  nectar

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Bat/mammal flowers
Pollination syndromes

• Nocturnal, white or drab, fermentation odor,
  large and sturdy, nectar and pollen rewards

Moth flowers

• Dusk and nocturnal, white, strong scent at night,
  long floral tubes, ample nectar

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Butterfly flowers
Pollination syndromes

• Diurnal, orange or yellow, weak scent, long
  floral tubes, ample nectar

Bee and beefly flowers

• Diurnal, often yellow or blue, with concentrated
  nectar rewards, bilateral symmetry, landing
  surfaces, nectar guides

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Carrion flies and beetles
Pollination syndromes

• Diurnal, brown or purple, smell of decaying
  protein, presented near ground, can be traplike,
  no reward

Female impersonators

• Some orchids are pollinated by deceit take
  advantage of naïve males, look or smell like
  female bees or wasps, no reward

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Plants and pollinators
Pollination syndromes

• Interactions are rarely specialized from both
  plant and pollinator perspectives
• Two exceptions obligate mutualisms between
  figs/fig wasps, yuccas/yucca moths

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Yuccas and figs
Pollination syndromes

• Insect pollinates flowers, lays eggs in
  developing fruit
• Insect larvae are seed predators
• An ongoing arms race fruits with too much
  predation aborted in yucca in figs, two kinds
  of flowers, only some can be predated

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Problem 5

• Delphinium nelsonii normally produces blue
  flowers but a few plants produce white flowers.
  Nick Waser and Mary Price wondered why white
  plants didnt become more common in the
  population over time. Interpret their data,
  below. indicates the two bars within a
  treatment differ.

Redrawn from Waser and Price 1983
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I dont have any hard evidence, Conniebut
my intuition tells me that Eds been
cross-pollinating.
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Breeding systems
Breeding systems

• Most appropriately, refers to variation in
  outcrossing rates
• Ranges from obligately self-pollinated to
  obligately outcross-pollinated

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Breeding systems
Vogler and Kalisz, Evolution 55202-204
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Why variation in selfing/outcrossing rates?
Breeding systems

• We see intermediates in animal-pollinated spp,
  but fewer in wind-pollinated species
• Intermediate selfing may have something to do
  with pollinators?
• Many models of the problemwe need to start with
  definitions

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Types of selfing
Breeding systems

• Geitonogamy selfing within a plant, via
  pollinator movement
• Large floral displays increase chance of
  geitonogamy

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Types of selfing
Breeding systems

• Cleistogamy obligate selfing within a flower
  that never opens
• Most plants with cleistogamous flowers have
  chasmogamous (open pollinated) flowers as well

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Cleistogamy and bet-hedging
Breeding systems

• A desert annual, Gymnarrhena micrantha
• Underground cleistogamous flowers produced
  regularly
• Outcrossed chasmogamous flowers produce smaller
  seeds with a pappus (for wind dispersal)
• More outcrossed seeds produced in wet (good) years

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Breeding systems
Am Nat 112636-639
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Types of selfing
Breeding systems

• Autogamy selfing within a flower. Three types,
  defined by timing and whether pollinators are
  required
• Prior
• Delayed
• Facilitated

Autonomous selfing
Pollinator required
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One mechanism of delayed selfing
Breeding systems
Dole 1992. AJB 79650-659
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When is selfing good?
Breeding systems

• Automatic transmission advantage
• Mixed mating parent contributes three gametes,
  outcrossing pollen or seed parent only two

Outcrosser
Mixed mating
Own seeds (male/pollen)
Own seeds (female)
Others seeds (male/pollen)
Own seeds (female)
Others seeds (male/pollen)
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When is selfing good?
Breeding systems

• No pollinators available (reproductive assurance)
• Selfing is good whenever it means you can have
  offspring by yourself.
• Bakers rule colonizing species are often
  capable of selfing.

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Reproductive assurance in Collinsia
Breeding systems

• Emasculated flowers can only make seeds if
  visited by a pollinator intact flowers can self
• Selfing ability usually related to flower size

E. Elle and R. Carney, AJB 90888-896
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When is selfing good?
Breeding systems

• Habitat is ephemeral (time limitation)
• Selfing adaptive in deserts or other ephemeral
  habitats, e.g. Clarkia, Collinsia

Runions and Geber 2000. AJB 87 1439-1451.
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When is selfing bad?
Breeding systems

• Pollen and Seed discounting
• Selfing reduces opportunities for outcrossing
  (your pollen or seeds are wasted on selfing
  reduction in outcross success discount)

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When is selfing bad?
Breeding systems

• Inbreeding depression
• Lower fitness of selfed relative to outcrossed
  progeny

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How is outcrossing enforced?
Breeding systems

• Herkogamy distance between anthers and stigma
  (usually a continuous variable)
• In Datura wrightii, greater outcrossing with
  increased herkogamy

Elle and Hare 2002. Functional Ecology 1679-88
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How is outcrossing enforced?
Breeding systems

• Heterostyly fixed differences in positions of
  anthers and stigma.

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How is outcrossing enforced?
Breeding systems
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How is outcrossing enforced?
Breeding systems

• Dichogamy differences in timing of different
  sex functions within flowers
• Protandry male first
• Protogyny female first

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How is outcrossing enforced?
Breeding systems

• Self incompatibility genetic systems that
  prevent (potential) relatives from making
  offspring
• Gametophytic SI haploid genotype of pollen
  grain recognized
• Sporophytic SI diploid genotype of pollen
  parent recognized

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Breeding systems
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Breeding systems
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Breeding systems
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Summary Pollination and Breeding Systems

• Floral morphology can often be used to form a
  hypothesis about both the pollen vector and the
  breeding system
• Breeding systems are highly variable in plants
  (because most are hemaphrodites) and are under
  complex selection

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Problem 6

• A researcher (Chris Eckert of Queens U.Im not
  making this up) has documented (using genetic
  markers) that selfing rates are high in Aquilegia
  canadensis. Design an experiment for Chris that
  will help him distinguish among four possible
  modes of selfing (geitonogamy and the three types
  of autogamy) that are possible in chasmogamous
  flowers. Be specific about your treatmentsnot
  how youll do them (I realize many of you wont
  know what columbines look like), but what you
  need to manipulate and/or control, and what your
  expected results would be, to experimentally
  address the question.