Biology 4250 Evolutionary Genetics

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Biology 4250 Evolutionary Genetics

• Winter 2007
• Dr. David Innes
• Dr. Dawn Marshall

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Outline of topics 1. Introduction/History of
Interest in Genetic Variation 2. Types of
Molecular Markers 3. Molecular Evolution 4.
Individuality and Relatedness 5. Population
Demography, Population Structure 6. Phylogenetic
Methods Species Level Phylogenies --------
Midterm break ---------------------
(Midterm test in lab. Feb. 26) 7.
Phylogeography 8. Speciation, Hybridization and
Introgression 9. Human Evolutionary Genetics 10.
Conservation Genetics
Background
Applications
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Individuality and Parentage

• Human Forensics
• Ramets and Genets (sexual and asexual)
• Genetic chimeras
• Gender ascertainment
• Genetic parentage

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Genetic Parentage - Situations

• 1. Maternity and paternity uncertain
• 2. Maternity certain paternity among candidate
  males
• 3. Hermaphroditic selfing
• outcrossing
• 4. Selfing vs. parthenogenesis

monogamy
polyandry
polygyny
polygynandry
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Genetic Parentage

• Primates dominant/subdominant males
• Birds extra-pair copulation
• Fish various monogamy ? polygynandry
• role-reversal

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Plant Mating Systems
In a word Diverse
Silene acaulis Gynodioecious (hermaphrodites
females)
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Plant Mating Systems

• Individual Flowers
• Hermaphrodite -- bisexual flower with both
  stamens and pistil
• Unisexual -- flower is either staminate
  (male), or pistillate (or carpellate) (female)
• Individual Plants
• Hermaphrodite -- the plant has only
  hermaphrodite flowers
• Monoecious -- unisexual male and female
  flowers are on the same plant
• Dioecious -- unisexual male and female
  flowers are on different plants
• Gynoecious -- has only female flowers
• Androecious -- has only male flowers
• Plant Populations
• Hermaphrodite -- only hermaphrodite plants
• Monoecious -- only monoecious plants
• Dioecious -- only dioecious plants
• Gynodioecious -- has both female and
  hermaphrodite plants
• Androdioecious -- has both male and
  hermaphrodite plants

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Parentage in Plant

• Paternal fitness
• ? spread of pollen (wind or insect)
• Mother known (seeds)
• - paternity to be determined

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Parentage in Plant

• Many plant species hermaphroditic
• Prevention of selfing (several mechanism)
• - M F mature at different times
• - anther stigma separation
• - genetic self-incompatibility
• - sex expression

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Prevention of Selfing in Plants
Primula veris

• 1. Spatial and Temporal
• - dichogamy (protandry and protogyny)
• - herkogamy (spatial separation)
• 2. Self-Incompatibility (SI)
• - homomorphic SI
• (gametophytic and sporophytic)
• heteromorphic SI
• (distyly and tristyly)
• 3. Sex Expression
• - monoecy, dioecy, gynodioecy, etc.

Style length
Thrum Pin
Pin Thrum
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Parentage in Plant

• 1. Relative proportion of selfing vs. outcrossing
• Mother known ? paternity assessed using genetic
  markers
• non-maternal alleles outcrossing
• Statistical models mixed mating model
• s selfing rate
• t outcrossing rate
• s t 1.0

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Out-crossing Rates

• Distribution of outcrossing rates Bimodal
• most species either predominantly
  outcrossing or selfing
• - Outcrossing selected when inbreeding
  depression high
• - Selfing selected in species that have purged
  recessive deleterious alleles
• Large variation among populations in outcrossing
  rate

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Outcrossing Rates
Pollination Wind animal
Variation among hermaphroditic species
Variation among populations
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Paternity in Plants

• 2. Outcrossing established determination
  Paternity
• - compare seeds (progeny) genotype with
  mother
• - deduce haploid genotype of fertilizing
  pollen
• - candidate fathers screened ? paternity
  exclusion
• - direct estimate of gene flow
• Example wild radish (Raphanus sativus)

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Paternity in Wild Radish

• - Self-incompatible, insect pollinated
• - Six highly polymorphic allozyme loci
• - Multiple paternity found for all maternal
  plants (85 of all fruits
• - Minimum of 2.3 paternal donors per maternal
  plant
• - Most multiply-sired fruits due to a single
  insect visit
• (pollen carryover)
• 44 of paternity from 100 m (gene flow between
  1 generation)

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Paternity in Moss

• Female (n) sporophyte (2n) ? deduce male (n)
  genotype
• Results
• - only 2/137 matings involved a single male
  not previously sampled in the area
• - at sites where both M F occurred, 93 of
  94 matings involved M F at the same site
• - Conclusion sperm dispersal limited

SS SF SM 2n S F M female S
S S male
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Other Topics in Parentage

• Sperm storage females can store sperm after a
• single copulation?
• - mammals few days
• - birds, insects weeks
• - salamander months
• - snakes, turtles several years

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Other Topics in Parentage

• Sperm and pollen competition
• - sperm from two or more males in direct
  competition
• for fertilization of eggs of a single
  female
• - many mechanisms for a male to ensure his
  sperm
• fertilizes a females eggs (paternity
  assurance)
• - plugs scoop out previous
  males sperm
• prolonged copulation multiple
  copulation
• with same female mate guarding
• Females may encourage sperm competition

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Other Topics in Parentage

• Sperm and pollen competition
• - multiply inseminated females? markers used
  to
• determine the success of each male
• first male, last male, no mating order
  effect
• Insects often last male has greatest
  fertilization success
• Plants pollination by multiple pollen donors
• competition ? rate of pollen tube
  growth
• usually advantage for first
  pollinating male

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Paternity Software

• http//www.bio.ulaval.ca/louisbernatchez/downloads
  .htm