Announcements

1
Announcements

• Lab 3 Information?webpage
• Midterm test Thursday Feb. 24
• Readings http//www.mun.ca/biology/dinnes/B2900/R
  eadings.html
• Summary topics, Example midterm questions
• http//www.mun.ca/biology/d
  innes/B2900/B2900.html
• Thursday Feb. 17 review Answers

2
Studies in Evolution

• Methods of Evolutionary Analysis
• Adaptation (Ch. 9)
• Sex and Sexual Selection (Ch. 7, 10)
• Life-history evolution (Ch. 12)

?
3
Sexual Selection

• Chapter 10

4

• Sexual Dimorphism
• Males and females often differ in size,
  appearance and behavior

?
?
Whats he on about ?
5

• Adaptive significance of sexual dimorphism??
• Sexual dimorphism difficult to
• explain by natural selection
• Example long tail feathers
• How can the evolution of sexual dimorphism be
  explained?

6

• Darwin and sexual dimorphism
• Challenges for passing on ones genes
• 1. Surviving
• 2. Reproducing
• And for sexual reproduction
• 3. Finding and mating with
  a
• member of the opposite
  sex

7

• Sexual Selection
• Differences among individuals at getting mates
• i.e. Mating success

8

• Sexual Selection
• Asymmetry
• - eggs are more expensive than ejaculates
• (eggs yolky sperm DNA propeller)
• - parental care by females, none by
• males (90 of mammal species)

9

• Sexual Selection
• Asymmetry
• Females
  Males
• Limits to of eggs of
• reproductive produced matings
• success

Access to females a limiting resource for males
10

• Batemans Experiment
• Test of asymmetric reproductive success
• D. melanogaster 3 virgin males
• 3 virgin females
• (each individual had 3 potential mates)
• Measured
• 1. number of actual mates
• 2. reproductive success ( of
  offspring)

11

• Results

(a)
(b)
(c)
Variance in reproductive success males gt females
12

• Results

Males reproductive success increases with
number of mates great variation
in the number of mates great
variation among males in reproductive
success Females no increase in reproductive
success with gt 1 mate less
variation in number of mates
little variation among females in reproductive
success
13

• Consequences of asymmetry
• (Female parental care)
• Males should be competitive (intrasexual
  selection)
• Females should be choosy (intersexual
  selection)
• Because females commonly invest much more
  per offspring than males

14
Sexual Selection

• Male-Male Competition
• combat
• sperm competition
• Infanticide
• alternative mating strategies
• 5. Female Choice
• 6. Run away sexual selection

15

• Male-Male competition
• (size matters)
• 1. Combat
• - favours larger body size
• - weaponry
• - armor

16

• Male-Male competition
• 2. Sperm competition
• Male mating success not determined by
  copulation but, whether his sperm fertilizes eggs

17

• Sperm Competition
• Internal fertilization
• If female mates
• with 2 or more males,
• sperm race to the eggs

18
Sperm Competition
M F offspring potential fathers

• external fertilization
• Internal fertilization
• - polyandrous species
• - socially monogamous
• species (extra-pair
• copulation)

19

• Sperm Competition
• Adaptations to increase chances of winning the
  sperm race
• Large ejaculates with many sperm
• prolong copulation
• mate guarding
• copulatory plug

20

• Sperm Competition
• Med. Fruit fly males
• sperm
• ejaculated
• 1. Private mating 1,379
• 2. With a potential 3,520
• competitor

21
Mate Guarding
Root Weevil
natural
22
Mate Guarding
Male barn swallows
Eggs laid
Female fertile period
23

• Sperm Competition
• Other Adaptations
• Damsel flies

Fig. 10.14
Removes sperm from previous mating
24
Sperm Storage

• Birds, insects, mammals
• Control of sperm use by female
• - Last male sperm precedence
• - First male sperm precedence
• - Mixing of sperm

25
Sperm Mixing(wood louse)

• Female Progeny Genotype
• 2/2 2/3 2/4 2/5
  2/6
• 2/2 2 10 7 21
  1
• Paternal alleles 2, 3, 4, 5, 6
• Possible male genotypes 2/3, 4/5, x/6
• (sperm from at least 3 males)
• 20 females gt 80 multiple
  paternity

26
Testes Size in bats- increased testes size with
increased group sizeadaptation to increased
sperm competition(correlation corrected for
shared phylogeny)
Fig 9-14
Testes size
Group size
27
An Evolutionary History of Sperm Competition T.
R. Birkhead (2000)
28
Sperm Competition
29

• Male-Male competition
• 3. Infanticide
• Pride basic social group of lions
• Newly mature males move to another pride
• New male kills nursing cubs
• - not his offspring
• - causes females to return to breeding
  earlier

30

• Male-Male competition
• 4. Alternative mating strategy

Female
Sneaky males
31

• 5. Female Choice
• Males unable to monopolize females
• Males advertise for mates
• Females inspect and choose
• sexual selection leads to elaborate
  courtship displays by males

32

• Female Choice
• Example
• Barn Swallows
• Males have longer tail feathers
• Used in courtship display

males
females
33

• Experiment
• (Anders MØller)
• Groups (males)
• 1. Shortened tail feathers
• 2. Control I (mock alteration)
• 3. Control II (unaltered)
• 4. Elongated tail feathers

34

• Results

Premating period second clutches
of fledglings
Demonstrates females prefer males with longer
tails long-tailed males have high RS
Fig. 10.17
35
Extra-pair copulation

• Shortened Control
  Control Lengthened
• tails I
  II tails
• By their
• female 0.036 0.014
  0.017 0.00
• pair-mates
• Females with the least desirable mate, had the
  highest rate of
• extra-pair copulations

36
Extra-pair copulation

• Paternity Analysis
• DNA fingerprinting
• Socially monogamous species (red-winged black
  birds) show extra-pair copulations
• 50 64 of nests

37

• Female Choice

• Why should females be choosy ?
• Male display an indicator of good genes
• Male free of parasites
• Acquisition of resources from males (gifts)
• Preexisting sensory biases
• Runaway sexual selection

38

• 6. Runaway Sexual Selection

• Example Stalk-eyed flies
• (Box 10.3)
• Females preferred males
• with long eyestalks
• 2. Males with long eyestalks left
• more offspring

39

• Runaway Sexual Selection

3. Sons inherit long eyestalks, daughters a
preference for long eyestalks (assortative
mating) 4. Each generation males have longer
eyestalks and females prefer longer
eyestalks 5. Positive feedback loop
40
Sexual Selection in Plants
Dimorphic
male
female
Wurmbea dioica
41
Sexual Selection in Plants

• Female invests more (seeds)
• Access to pollinators limits mating success in
  males more than females
• Increased flower size in males increases
  pollinator visits

42
Sexual Selection in Plants

• Male-Male competition
• - pollen tube growth
• (sperm competition)
• Female Choice
• - manipulate pollen tube growth
• - selective seed abortion

43
Sexual Selection in Humans

• Cognitive processes underlying human mate choice
  The relationship between self-perception and mate
  preference in Western society
• Peter M. Buston and Stephen T. Emlen (2003) PNAS
  1000, p. 8805
• We conclude that, in Western society, humans use
  neither an opposites-attract nor a
  reproductive-potentials-attract decision rule
  in their choice of long-term partners but rather
  a likes-attract rule based on a preference
  for partners who are similar to themselves across
  a number of characteristics.
• 10 Characteristics indicative of
• - wealth and status
• - family commitment
• - physical appearance
• - sexual fidelity
• 
  (1000 Cornell University undergraduates)

44

• Sexual Selection

Summary 1. Differences among individuals at
getting mates 2. Asymmetry in limits to
reproductive success - females
of eggs - males of
matings 3. Male competition, female choice
45

• Sexual Selection

Summary 4. Reversed when males invest more than
females ( male parental care pipe
fish) 5. Principles of sexual selection in
animals can be applied to flowering plants
46

• Sexual Selection

Dr. Ian Jones (Biology) Sexual selection in
Auklets
Aethia pygmaea I. Jones
47
Studies in Evolution

• Methods of Evolutionary Analysis
• Adaptation (Ch. 9)
• Sex and Sexual Selection (Ch. 7, 10)
• Life-history evolution (Ch. 12)

?
?
48

• Life History Evolution
• Evolution by natural selection has modified all
  organisms for one ultimate task
• to reproduce
• (sexual selection one aspect)
• How organisms carry out this task enormously
  diverse

49

• Life History Diversity
• Mammals
• Mice mature early, reproduce quickly
• Bears mature late, reproduce slowly
• Plants
• annuals live 1 year then die
• perennials live gt 1 year
• Bivalves
• oyster 20 million eggs (0.05 mm)
• clam 100 eggs (0.30 mm)

50

• Life History Evolution
• Attempts to explain the diversity of
  reproductive strategies
• Trade-offs constrain the evolution of adaptations
• Balance costs and benefits to maximize
  reproductive success

51

• Life History Evolution
• Organisms cant
• - mature at birth
• - produce high-quality offspring
• in large
  numbers
• - live forever
• Energy available for each activity finite
• trade-offs

and
and
52

• Life History Evolution

Pattern of Energy
Allocation Opossum Life-History
Fig. 12.2
53
Mussel life history
Spat
Settlement
Planktonic larvae
54

• Life History Evolution
• Environmental variation the source of much of the
  observed life history variation
• Question
• 1. Why do organisms age and die ?

55
Reproduction and Aging (senescence)
Fig. 12.4
56

• 1.Why do organisms age and die ?
• Aging (senescence)
• late-life decline in fertility and
  survival
• Aging reduces fitness and should be opposed by
  natural selection
• M. R. Rose (1991) Evolutionary Biology of
  Aging

57

• Theories of Aging and Senescence
• Rate-of-living theory
• Evolutionary theory

58

• Theories of Aging and senescence
• 1. Rate-of-living theory
• aging due to the accumulation of
  irreparable damage to cells and tissues
• (Prediction high metabolic
  rate shorter life span)
• lack of genetic variation for selection
  against aging
• (Prediction selection can
  not lengthen life-span)

59

• Theories of Aging and senescence
• Rate-of-living theory
• Prediction high metabolic rate shorter life span
• all species should expend about the same amount
  of energy per gram of tissue per lifetime
• - slowly over a long lifetime
• or - rapidly over a short lifetime
  

60
Fig. 12.5
Great variation
61

• Theories of Aging and Senescence
• Great Variation in metabolic rate among
  mammals
• - elephant shrew (36 kcal/g/per lifetime)
• - bat (1,102 kcal/g/per lifetime)
• Marsupials significantly lower metabolic rates
  and
• significantly lower life spans
• Variation in rate of living cannot explain
  variation in aging

62
Increased life span in Drosophila
Selection for increased life span
Fig. 12.6
Select for early and late reproduction
63

• Theories of Aging and Senescence
• 2. Evolutionary Theory of Aging
• aging caused by failure to repair cell and
  tissue damage
• Accumulation of deleterious mutations
• Trade-offs between repair and reproduction

64

• Evolutionary Theory of Aging
• Simple Genetic Model (Fig. 12.9)
• (a) Wildtype matures at age 3 dies at age 16
• (b) Mutation matures at age 3 death at age 14
• (c) Mutation matures at age 2 death at age 10

65
(a) Wild Type
sum
66
(b) Mutant
sum
67
(c) Mutant
sum
68
Fig. 12.9a
1
0.640
area
0.317
0.079
(b) 2.419 0.079 2.340
(c) 2.419 (0.0790.317) 0.640 2.663
69

• Evolutionary Theory of Aging
• Fig. 12.9
  Lifetime Repro.
• 
  Success
• (a) Wildtype
  2.419
• (b) Mutation earlier death 2.340
• (c) Mutation trade-off early 2.663
• reproduction and early death

70

• Evolutionary Theory of Aging
• Interpretation
• 1. deleterious mutations with effects late in
• life only weakly selected against
• 2. Mutations with benefits early in life and
• deleterious late in life favoured
• (antagonistic pleiotropy)
• trade-off between early reproduction and
  survival late in life

71
Inbreeding depression andAge
Fig. 12.9
NS acts more weakly on late-acting deleterious
mutations Inbreeding depression increases with age
72
Trade-off in Reproduction
Fig. 12.13a Collared flycatcher Early
reproduction Smaller clutch size
Breed at age 2
Breed at age 1
73
Trade-off in Reproduction
Extra eggs
Female given extra eggs show a decline in clutch
size
Control
Increased reproduction early in life ? decreased
reproduction later in life
74
Trade-off between energy for reproduction and
later survival in plants
Pairs of closely related species Annual gt than
perennial
75

• Evolutionary Theory of Aging
• ETA can explain variation in life history
• Strength of Natural Selection declines
  late in life
• Question
• What is the relative importance of
  deleterious mutations and trade-offs in the
  evolution of senescence ?

76

• 2. How many offspring to produce?
• Trade-off fixed amount of energy and time
• the more offspring produced,
• the less time and energy to devote to
• each one

77

• Clutch Size in Birds
• (David Lack, 1947)

Selection will favor the clutch size that
produces the most surviving offspring Assumption
probability of offspring survival decreases
with increasing clutch size (Fig. 12.16)
(the more kids, the less food for each)
78
Clutch SizeFig. 12.16
Prob. of surviving (P) 0.5
of surviving offspring (CS x P) 5 x 0.5 2.5
Intermediate optimum
79
Great tits (Parus major)
young surviving per clutch greater than average
clutch size
8.53
12
80
Clutch Size

• Clutch size lt surviving per clutch
• Birds producing fewer eggs than
• optimum ?
• Other costs
• - trade-off between parents
• reproduction and survival
• - large clutch size may impose other
• costs than just survival ? next

81
Fig. 12.18
Daughters clutch size
Eggs removed
Eggs added
82
Clutch Size

• Trade-off between offspring quality and quantity

83

• 3. How big should each offspring be?
• Trade-off fixed amount of energy
• - many small offspring or
• - few large offspring
• Size number trade-off

84
Fish Fruit
flies
Fig. 12.21
Clutch Size
Egg Size
85
Fig. 12.22
Number 10/size
86
Fig. 12.22
Survival 1- (1/size)
87
Fig. 12.22
Parental Fitness Number x survival
1.6 2 x .8
88

• Offspring Size
• Conflict of interest between parents and
  offspring
• Parents
• - selection can favour smaller offspring
  than optimal for offspring survival
• Balance between offspring size and survival
• Optimum varies with environment

89

• Life History Evolution

Summary Aging and Senescence trade-off
between reproduction and repair Offspring
number trade-off between clutch size and
offspring survival Offspring size
trade-off between offspring size and number
trade-off between offspring size and survival
90
Principles of Evolution and Systematics
First Half Topics

• Introduction (Evolution thinking)
• The evidence for evolution (Relatedness of life
  forms)
• Darwin Natural selection (Galapagos Finches )
• Population Quantitative genetics (Genes in
  populations)
• Natural selection Adaptation (Form and
  function
• 
  Sexual
  selection)
• Adaptation and Diversity

91

• Coming Next
• The History of Life
• (in 12 lectures)
• Narrated by Dr. Ted Miller
• Tuesday March 1, 2005
• Show times 1030 1145