breeding and mating system evolution: variation in...
TRANSCRIPT
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Breeding and Mating System
Evolution:
Variation in Breeding Systems
Lecture 7: Spring 2013
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Plant Breeding systems = Attributes of the flowers
within an individual that may influence gamete
transfer among conspecifics
Animal Breeding systems ~ tend to use breeding
system w/r to crossing programs to acquire
particular traits.
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Mating system = who you mate with
• Outcrossing rate = t
• Ranges from 0 to 1.0 where 0 is total
obligate selfing and 1.0 is obligate
outcrossing.
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Mating system & breeding system
differences between plants & animals
Animals
Mobility
Many dioecious
Some hermaphroditic = both sexual functions within a
single individual (especially invertebrates).
Plants
Lack mobility compared to animals
Hermaphroditic
selfing -----> outcrossing -----> dioecy
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Gene Flow in Plants
(1) Pollen – deposition and loss (Inouye et al 1994)
(2) Seed Dispersal
Primary – dehiscent, indehiscent, ballistic, passive
Secondary – ants, rodents, mammals, humans
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Pollen Types & consequences for dispersal
Granular – ex.
Pollinia – ex., orchids
http://bio100.nicerweb.net/Locked/media/ch21/orchid_wasp_pollinia.jpg
http://t2.gstatic.com/images?q=tbn:ANd9GcR8xGViQGQHJlmwmqXU7OKKMWeatRSnC50Dwz
Wv2z3VvaDzadc&t=1&usg=__x8XDsnaT9xLmuTaQdfFvTRQ9V-U=
http://upload.wikimedia.org/wikipedia/commons/e/e0/Bee_covered_in_pollen.jpg
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Pollen Dispersal curves
1) Biotic, animal pollination - nearest neighbor on
scale of few meters in many instances ~
negative exponential
2) Abiotic, wind pollination ~ negative exponential
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Primary Seed Dispersal Curve
http://www.pnas.org/content/102/10/3726/F5.large.jpg
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Methods of seed dispersal
http://www.puc.edu/Faculty/Gilbert_Muth/art0071.jpg
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Primary and Secondary seed dispersal
http://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Ricinus_
March_2010-1.jpg/456px-Ricinus_March_2010-1.jpg
Monoecious Ricinus communis
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Mechanisms thought to aid gamete transfer:
• Autogamy – repro. assurance
• Cleistogamy – repro. assurance
• Geitonongamy – within plant selfing (between flowers of same
indiv.)
• Dichogamy – temporal separation of male and female function,
promote outx, gamete transfer
• Herkogamy – spatial separation of male and female function,
promote outx, gamete transfer
• Protandry- hermaphrodite exhibits male fn before female fn
• Protogyny – hermaphrodite exhibits female fn before male fn
• Self–incompatibility – similar S alleles, promote outx by
preventing selfing and related individual matings
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Chasmogamy and Cleistogamy:
violets
Specularia biflora
http://www.missouriplants.com/Bluealt/Specularia_perfoliata_flower.jpg http://t2.gstatic.com/images?q=tbn:ANd9GcTY2mWmQvZ7BEtAUV3bY6KavvANaAzzL92FPET7
pwwTIPDMHrM&t=1&usg=__J5KvvDL2v42QYgvcguAT5J0elqM=
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Specularia biflora (Campanulaceae) – hermaphroditic and protandrous
http://t3.gstatic.com/images?q=tbn:ANd9GcQyGMZb3
fL4g7tpwBraypu8HwphgFMRDYQ8WJuXrsGYTGoirY
U&t=1&usg=__tT2nbNBN0V5vRKzsoueIFUtQMJg= http://www.missouriplants.com/Bluealt/Specularia_perfoliata_flower.jpg
1st Male phase flower 2nd Female phase flower
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Monoecy: Begonias
https://encryptedtbn0.gstatic.com/images?q=tbn:ANd9GcRUqGQz2HyCED4P
bmuMh72PT5WU2yRijoyf4UeWRsaCfCZd-xf3Ng
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Dioecy: willow tree and many animals
http://fiddleheadcreek.com/wp-content/uploads/2012/04/male-and-female-catkins.jpg
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Tristyly –legitimate vs. illegitimate crossing (Darwin 1876)
L M S
ssmm ssMm
ssMM
SsMm
SsMM
Ssmm
http://sakaiweller.bio.uci.edu/images/pcArray3types-464.jpg
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Types of self incompatibility
Gametophytic Sporophytic
Rxn determined by
pollen genotype
Rxn determined by
sporophyte genotype
Stylar inhibition Stigmatic inhibition
Binucelate pollen grains Trinucleate pollen grains
Ex., Legumes, Roses,
Lily, tomatoes
Ex., Asteraceae
(composites~ sunflowers
and daisy), Brassicaceae
(crucifers)-many crop
plants )
stigma
style
ovary
anther
filament
Stamen = anther + filament
Pistil = stigma + style + ovary
ovule
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Sabatia angularis (Gentianaceae)
Male fn
Herkogamy and Dichogamy
Female fn
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• Temporal separation between male and female function (dichogamy) appears to be better than physical separation between male and female function (herkogamy) in avoiding within flower selfing when both nectar and pollen are rewards.
• If pollen the only reward, then….floral blooms are more likely to be herkogamous than dichogamous
Sabatia angularis
Gentianaceae
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Why one species has both mechanisms?
• Prevent within flower selfing
• Increase efficiency of gamete transfer through
preventing interference between male and female
sexual function
• Pollen limitation in many systems – variable and limits
female reproductive success (Dudash 1991; Dudash and
Fenster 1997; NCEAS working group: Ashman et al 2004.; Knight et al.
2005)
• Separate Functions:
– Pollen presentation
– Pollen receipt
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Animal issues
Most dioecious, but some exhibit other breeding systems
Inbreeding in animals
– Biparental inbreeding (loss of heterozygosity not as severe
as when plants self-pollinate and they decrease het. by 50%
each generation).
How do animals attain gene flow?
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THE INBREEDING COEFFICIENT (F)
The inbreeding coefficient of an individual refers to how closely related its parents are.
When parents are unrelated, offspring F = 0, for completely inbred individuals F = 1.
Levels of inbreeding in offspring for different kinds of relationships among parents are:
______________________________________________________________
Parents Offspring F
______________________________________________________________
Unrelated 0
Brother-sister, mother-son, or father-daughter 0.25
Half brother-half-sister (half sibs) 0.125
First-cousins 0.0625
Second- cousins 0.0156
Self-fertilization 0.5
______________________________________________________________
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Types of mating systems:
1) Asexual ~ Vegetative (offspring sprout from body of adult and then separate) – stolons-plants, budding-animals via fission (mitosis)
2) Parthenogenisis – animal young produced without meiosis (unfertilized egg develops into an adult animal)
Apomixis = seed production in plants without meiosis (unfertilized ovules develop into a diploid seed and then plant)
3) Change/switch sex – often dependent on some resource ex.,
Issues of internal vs. external fertilization and parental care
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Asexual or Parthenogenetic Reproduction:
• Ubiquitous
• Frequently much rarer than sexual reproduction
• Syngamy or fertilization does not occur
• Definition: production of offspring which are
identical to the parents.
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Apomixis: The Dandelion
Ode to an Apomict: The Dandelion Daughters have I many
Yet husband and father none
A perfect matriarchy
I sit here in the sun
And send my plumed children
Floating one by one
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Parthenogenesis: aphids, lizards,
Daphnia, and boa
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Sex switchers: jack in the pulpit & some fish species
Rainbow trout
Clown fish
Jack in the pulpit
http://www.aquaticcommunity.com/clownfish/clownfish.jpg
http://www.3quarksdaily.com/3quarksdaily/2006/02/sperm_cells_tur.html http://americanhiking.chattablogs.com/archives/Jack%20in%20the%20Pulpit
%20Side%20View%20resized.JPG
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Types of mating systems:
4) Hermaphrodite - sexual repro. without partner
5) Polygamy – one male and many females
6) Polyandry – one female and many males
7) Monogamy – partners for life
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Hermaphroditic flower:
http://upload.wikimedia.org/wikipedia/commons/4/4e/Tulip_Tulipa_clusiana_%27Lady_Jane%27_Rock_Ledge_Flower_Closeup_3008px.jpg
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Hermaphroditic Animals: snails, worms
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Polygamy: one male & many females (harem)
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Polyandry: much rarer mating system
• Jacanas, one female brightly colored &
many males
What other females practice a form of polyandry?
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Monogamy:
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Highlights/Questions?
• Great variation in breeding/mating systems for both plants
and animals
• Plants have gone to great lengths to direct their gametes to
conspecifics
• Animal mating behaviors achieve many of these same goals,
such as mating between unrelated conspecifics
• What facilitates the evolution of these traits and behaviors?