University of California at Santa Barbara

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University of California at Santa Barbara

• Susan Mazers Lab
• Ed Lowry

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Questions

• Can inbreeding depression be a function of
  environmental conditions?
• Can inbreeding depression be related to mating
  system?
• Can inbreeding depression be related to
  population size?

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• An experimental test of how inbreeding depression
  (IBD) changes over an environmental gradient
• An attempt to relate measured values of IBD to
• mating system (self-fertilizing vs. outcrossing)
• population size

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Can inbreeding depression be a function of
environmental conditions?
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Can inbreeding depression be related to
population size and mating system?
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Clarkia is a genus of annuals found in the
western U.S.

• 59 species
• Grow winter to spring
• Various distrib./pop. sizes (6 endangered, 20
  rare or uncommon)
• Mating system can be selfing, outcrossing or
  mixed mating

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Four Taxa

• Clarkia unguiculata
• Clarkia exilis
• Clarkia xantiana
• ssp. xantiana
• ssp. parviflora

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Ten populations
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Simulate an environmental gradient

• Water is of paramount importance to a flowering
  annual in the southern Sierra
• Create five treatments of water availability

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Produce an F1 generation of offspring from self-
and outcross-matings
Parent generation
F1 in water treatments
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Grow to maturity

• Monitor survivorship
• Measure seed yield (collect and weigh all seeds
  gt total seed mass )

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Seed mass per ind. for C.unguiculata

• N 120 for each treatment
• H2O amounts made each treatment distinct

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IBD for C. unguiculata
F 7.03 P 0.001
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IBD for 3 populations of C. unguiculata
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IBD for C. exilis (selfer)
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IBD for 3 populations of C. exilis
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IBD for C. xantiana ssp. xantiana
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IBD for 2 populations of C. xant. ssp. xantiana
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Inbreeding depression vs. population size
r2 0.88 p lt 0.001
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Inbreeding depression vs. population size
r2 0.88 p lt 0.001
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Inbreeding depression vs. population size
r2 0.88 p lt 0.001
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Inbreeding depression vs. population size
r2 0.88 p lt 0.001
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Thank youSusan MazerBrent MillerHoracio Paz