Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Experiments to:
·
·
·
·
·
·
·
·
·
·
·
·
·

Explain sex ratios
Explain why some species reproduce asexually and others sexually – why sex?
Explain why there is local population variation in traits
Explain why there are 2 sexes & what determines
Investigate sexual selection (male-male, sexually antagonistic coevolution, female choice)
Explain how MHC influences sex & mate choice
Explain genomic conflict & sex ratio distorters
Evidence Fisher’s theory & Hamilton’s
1
...
There was a transition to anisogamy with origin of males and females, which is common in
multicellular eukaryotes
...
Means equal
parental investment
...

Tilquin & Kokko (2016) – Geography of parthenogenesis – Asexuality most prevalent in marginal habitats as
well as newly colonisable areas, or where abiotic selection pressures are relatively stronger than biotic
...

Also get reproductive assurance in newly colonisable areas so asexuals outcompete sexuals
...
Microbes fungi and plants evidence for negative conditiondependent sex – poor condition individuals more likely to reproduce sexually – is evolutionarily advantageous
under wide range of settings
...
Could be to adapt better to areas undergoing
significant environmental change
...

Beekman et al (2016) – Sexual selection in hermaphrodites, sperm- and broadcast spawners, plants and fungi
...
Don’t really get
hermaphrodite stuff
...

Haig (2016) – Bryophytes – Multicellular haploid gametophytes produce gametes by mitosis
...
Can result in unisexual
populations unable to reproduce sexually
...
Haploid selfing is common in bryophytes with bisexual gametophytes, and results in completely
homozygous sporophytes
...
This process can be considered analogous to 'asexual' reproduction with 'sexual' reproduction
occurring after rare outcrossing between haploid parents
...
This difference is probably
related to clonal growth and vegetative competition occurring in the haploid but not the diploid phase in
bryophytes, but the reverse in ferns
...
Origin of sex: why sex is beneficial
a
...


Features of sex
i
...
Fisher 1930, Muller 1932
i
...

ii
...
Sex speeds evolution only if DIFFERENT individuals with DIFFERENT beneficial mutations
iv
...
Goddard 2014-sexual species of yeast gained beneficial mutations and adapt better than asexuals, but done in
lab
...

Purges deleterious mutations by bringing bad genes together to fight Mullers Ratchet

...
Spatial heterogeneity hypothesis- sex favoured in heterogeneous environment
...
genetic drift inevitable in a small population
d
...
Williams 1966
i
...

e
...
Hamilton 1980
i
...
common genotypes are at greater risk
iii
...

Purge synergistic deleterious genes

...
similar to mullers but for individuals not groups and also for synergistic genes not just bad like fisher-muller
g
...
two fold cost
i
...
finding a mate hard
iii
...
TFFMS
2
...
Mancebo-Quintana 2012-Origin of sex has 2 problems: 1: need for a
gamete to find partner to merge with; cost in time and energy
...


2
...

Game Theory

...
Game Theory used to determine evolutionarily stable strategy
i
...
Large can fuse with small but small cannot fuse with small
...
Charlesworth 2010: Anisogamy evolved independently in many lineages
but green alga good to study because chlamydomonas are isogamous
whilst volvox are anisogamous
...

Genomic Conflict

...
Cytoplasmic conflict costly to nuclear genes
...
Unilateral destruction of cytoplasmic genes prior to fusion, or…
2
...
e
...

ii
...
2 gamete types: suppressor and
non-suppressor types
b
...
Heterogamety and multifactor (>2 sex chromosomes)

1
...

2
...

3
...

mammals, most amniote vertebrates
i
...
Female store sperm by releasing sperm or not as egg laid
...

Gempe 2009: honey bees: single sex determination locus defines sex, as encodes splicing factor which
targets feminiser gene the transcript of which is spliced differently in males and females
...
csd gene arose recently by gene duplication from
ancestral progenitor fem gene and then positive selection in duplicate, favouring presence of upstream signal
that resulted in novel sex determination system in honey bees
...
The reduction of meiotic recombination that is observed at the sex determination locus of the
honey bee may also indicate that the csd gene will gradually degenerate over time (Charlesworth et al
...

Environmental sex determination

...
Control over sex of offspring by controlling temperature, put more/less
vegetation on
...
Implications from climate change if cant reduce/raise the temperature get
uneven sex ratio
3
...

turtles and squamates
a
...
Sequential hermaphroditism
1
...

Theory of sex allocation

...
Reproductive value increases with age/size/condition, but effect of size is greater for males
...
Here, females have higher values when
small/young, but males have higher value when large/old
...
Other way round; effect of size is greater for females than males
...
Sperm competition


...
Darwin introduced male male competition 1871 and female choice from sexual selection
...

Features of sperm

...
Cohen 1973 – meiosis errors
...
Parker 1982 – sperm competition
...
Sperm size for speed or power
1
...

External fertilisation more but smaller
2
...



...

a
...
Positive correlation with sperm length
...
Sperm dimorphisms to block up female
1
...
Sperm evolving large size to block up female storage
tubules in drosophila
...
Cook and Weddell 1995
...
Accessory fluids
1
...
Chapman 1995- Drosophila toxins incapacitate other male sperm
3
...
Antagonistic coevolution because female can evolve resistance
...
Lumley 2016: evidence that females improve offspring fitness by mating with multiple males but found no
evidence that gamete-specific interactions (sperm competition) allow offspring fitness benefits when
polyandrous fertilization conditions provide opportunities for sperm competition and cryptic female choice
v
...
testis bigger in multiple mating species
2
...
plugs and chastity belts

4
...

Sperm Removal

...

Internal fertilisation

...

Prolonged copulation

...
The male acts as a ‘plug’
c
...
lions 100 times a day for a week
d
...

Forced copulation

...
In a hermaphrodite marine flatworm, sperm injected directly into the body cavity (where the eggs are)
...
Bean weevil has spines on penis that damage female
ii
...

Plugs and chastity belts

...

Bose 2016: Effort spent on raising unrelated offspring can be costly and wasteful, and parents are
expected to reduce their level of investment when they have low or uncertain relatedness to the young under
their care
...
Nest
takeover: male displaces another male from a nest, is a reliable indirect cue of paternity causes drop in
offspring survival
...
Female Perspective


...
Fertility insurance
i
...


Dunnocks: each male want full paternity but female mate with beta male
so will care also

ii
...
Better genes
iv
...


Superb fairy wren: monogamous species but females mate in secret at
night to increase genetic diversity

1
...
But done in inbred population so results of genetic
diversity easier to see
Baer and Schmid hempel 1999: honeybee resist parasites
...


a
...
Eject sperm from subdominate male (chickens)
i
...
This may have been due to fertilised eggs from
genetically similar mates having lower viability
b
...
TRIVERS 1972: Males produce lots of cheap gametes
...
Males can
increase fitness by mating many times
...
Therefore, intense competition between M to mate with more than one

6
...

Benefits of female choice

...
Heritable
1
...

Fishers runaway process
i
...
Norris 1993
2
...

cross-fostering chicks, and showed that stripe
width is correlated with the stripe width of the
genetic father, and not with the fostered father
...
female preferences are heritable
1
...
attractiveness & preference must covary
1
...
stalk eyed flies
iv
...
more sons if attractive
male
2
...

Zahavi handicap principle

...
Norris 1993
2
...
Evans 2004
a
...

From the GENE PERSPECTIVE

...
beneficial effect of allele in one sex but not other: x and y chromosomes
ii
...
Rice 1996 was experiment
...
Drosophila: high conflict line females mate polyandrously and one
monogamously
...
47 generations: longevity of monogamous lines higher because in other
male only interested in his current brood so harm female
3
...


Low overall reproductive rate of polyandrous line show cost of sexual
conflict
c
...
Thus, to our knowledge, we provide the first comprehensive evidence of postmating (as well as
premating) reproductive isolation due to sexual conflict
...
Maintaining Genetic Diversity


...

recurrent deleterious mutations
b
...
Parasite theory
1
...
Milinski 1990: sticklebacks
3
...
So maybe not because shades of RED can’t be discriminated, but
because they just look weird, or the females are scared under the odd
lighting
4
...
Moller 1988: swallowbirds
1
...
long tailed male signals condition get more EPC from female with short tail
mates, pair faster, fledge more young

...
What do females get?
1
...
Heritable benefits

...
Half brood fostering experiment
i
...

Different about resistant males?

...

Mate choice

...
Yamazaki et al
...

can discriminate based on one MHC gene difference in mice pups
2
...

perfume experiment but only done on 36 people
3
...
Women prefer MHC dissimilar males, on pill prefer similar

...
But not all studies find this pattern, in humans or other animals- Kamiya et
al 2014 meta-analysis suggests there’s general female trend for
dissimilarity, but differs significantly between species
6
...


...

Took several steps before the experiment to improve chances of getting a positive result (males had
to wash with perfume-free soap before tests female used nose spray
i
...
Inbreeding avoidance

...
But populations were small and already inbred,
therefore inbreeding IS a problem
...

MHC-based odour can be used for kin recognition; has nothing with inbreeding avoidance
...

For example, female mice prefer to breed and nest with close kin, use odour as cue: Manning 1992
...
Heterozygote advantage

...

Paterson et al 1998: Soay sheep: found nematode resistance higher in ONE PARTICULAR MHC
genotype, but that heterozygosity was not related to resistance
...

Penn 2001 - HLA (MHC complex in humans) heterozygotes show no advantage over homozygotes
against malaria
...
Red Queen hypothesis

...

Penn & Potts infer that it probably happened because of differential spontaneous abortion – under
disease risk the heterozygous zygotes were more likely to make it to full term
...
Schuster 2016: Key genes of adaptive variation are encoded by the immune
genes of the major histocompatibility complex (MHC) playing an essential
role in parasite resistance
...
We concluded that selection
processes seem to be strong enough to maintain moderate levels of MHC
diversity in our study populations outcompeting genetic drift, as the same
MHC alleles were conserved between years
...



...
Sex Ratios
genomic conflict

a
...
Nasonia msr is the degenerate bacterium
1
...
1991 gave asexual Trichogrammar species antibiotics
...
Fishman 2018: Maternal testosterone: Nutria is a polygynous rodent that shows fluctuating sex ratios
...
Litters of high testosterone females had female-biased sex ratios
...

Paternal sex ratio

...
Edwards 2016: Assumed male contribution is 50/50 female to male, investigated sperm sex ratios in a
mammalian species: show significant variation
...
So have possibility of adaptive paternal
control of sex allocation
...

Meiotic drive in Aedes

...
meiotic drive gene: 2 linked genes one gene breaks down x other confers resistance to self on y
...

ii
...
Long term evolutionary conflict in all male population would go extinct
d
...
Explain evolution of genetic sex determination, and why sex chromosomes don’t cross over
i
...
The nearer you get to sry, the more genetically different the genes on X
and Y are, suggesting they stopped crossing over further back in time
e
...
Haig & Grafen 1991 suggested recombination at meiosis might have evolved as way of getting rid of problems
of meiotic drive and spread of selfish gene by crossing over separating the 2
...
drive genes are 2 linked genes poison and antidote
2
...
why meiotic drive genes seen on sex chromosomes that dont cross over
i
...
resistance evolves in other chromosomes
2
...
Haig and Grafen: recombination evolved to stop spread of selfish genes by
splitting linked genes
f
...
Some genes must come from each parent: imprinted only in mammals and flowering plants
...
De-imprint the genes and foetus is fine
...
Result of sexual conflict: genes battle
...
P
...
polionotus: monogamous
...
Monogamous females weak at resisting promiscous male genes: giant
babies
3
...

Fisher’s theory of sex ratio

...
When sexes are equal and whole population interacting:
ii
...

Individually advantageous
iii
...
ESS ARGUMENT
iv
...
Testing Fishers Theory
2
...

Made fewer males: female bias and vice versa to ESS
3
...
Sexes are not equal to produce:
1
...
So get equal investment because males get same fitness
as females: twice the mating success
2
...
Mammals:
1
...

growth rate in utero, need more milk and mom in worse condition after
...

a
...
Local resource competition
1
...
Hewison 1995: same in Roe deer
i
...
Sometimes costs of investment are repaid
2
...
In new pack male biased ratio and
mothers should bias to sex that helps
3
...

Hamiltons sex ratio theory


...
Result when relatives interact with each other: experience competition for resources or benefited from
presence of other relatives ratios skewed
1
...
Males die, females covered
in pollen and leave (symbiosis): female biased sex ratios
ii
...
in an isolated population: wont interact with all of population (fisher)
2
...
in fig example: diminishing returns from investing in males because sons
compete with each other and the resources put into these sons could have
gone into daughters and so granddaughters

...
Testing Hamiltons theory and meeting fisher
1
...
More females into fig: more males: move from LMC and
see fisherian sex ratio
2
...
Sex ratios of broods with one or two females

...
Superparisitism

...

Macke 2011: Spider mite: 3 levels of LMC: 1/10/100 foundresses (fisher): higher male ratio each time
until 50:50
...

Conflict over the sex ratio

...
Reproduction in social hymenoptera: relatedness between interested parties differ not just mother allocating
resources
...
Basis of model: fishers sex ratio theory and hamilton’s kin selection
1
...
75, worker brother 0
...
If relatedness
asymmetry = 1 expect equal investment (fisher)
2
...
workers 3x related to sisters expect 3:1
...
Argued workers have control and 3:1 ratio, recent analysis suggests proportion invested is 0
...
75
...
Multiple mating?
2
...
More than one queen?
1
...
Across 25
species of polygynous ants investment in daughters is 0
...
Colonies differ in queen mating pattern?
1
...
Boomsma and Grafen 1991: colonies differ in relatedness asymmetry
...
Relatedness asymmetry higher than average in single mated colonies: females
vii
...
Sundstrom 1994: wood ants found it was true
j
...
fisher modelled population equilibrium reached by selection but not all individuals are same or face same local
conditions
i
...
LMC

...

Herre: fig wasps
b
...
Local sex ratio


...
If population = no advantage to deviating from ESS
...
Woodchuck: females removed
...
Trivers Social Evolution: Humans
...
maternal condition

...
mothers base sex ratio based on condition and ability to invest in offspring
i
...

ii
...
Silver spoon effect: life long reproductive
advantage for an individual that had access to
abundant resources during early part of life
...
Condition of young after investment depends on
condition of mother
3
...
Males gain more from improved condition
iii
...
big male > big female
...
Good condition have son, poor have female
a
...
Size
i
...
Red deer: Dominant female: better condition,
breed earlier and have higher LRS because live
longer
...

Subordinates have more daughters
2
...
Rhesus Macaques: dominant females better at
protecting daughters from harassment from
males: have more dominant daughters: produce
more daughters
ii
...
Seal: sexually dimorphic species, breed early
pups have longer to suckle so more sons earlier
2
...
Probability of breeding as yearling: female
constant but male decrease with age
...

iii
...
may have more experience: late reproduction
benefit in LHT: lower juvenile mortality and
higher fecundity
b
...
tested using mammal data
i
...
Host size: parasitic wasps: one egg per host
...
Host size determine adult size, female gain more
if large than male
2
...
Prediction: host size is important in sex ratio

a
...
Better fit to step function
...
Territory quality experiment: Komdeur 1997: Seychelles warbler
1
...
Female helpers
...
Helper is good or bad
depends on quality of territory
2
...
Bad quality: detrimental so LRC: 77% male bias
as disperse
4
...

Produce daughters and change is not due to biased death or embryos
c
...
No simple equation: hard to make quantitative prediction
i
...
What matters is ability to leave
descendents into future so reproductive value not numbers
ii
...
Maternal effect not condition
iii
...
Size of son and rank of daughter
iv
...
Sex ratio and doesn’t consider clutch size: Life History Theory
vi
...
Using two-sex models parameterized with data
from free-living mammal populations with contrasting levels of sex differences in demography, we
demonstrate how sex differences in life history traits over the entire lifespan can lead to a wide range of sex
allocation tactics, and show that correlations between maternal condition and offspring sex ratio alone are
insufficient to conclude that mothers adaptively adjust offspring sex ratio
...
Absence of helpers

9
...

Life history theory seeks to explain how natural selection and other evolutionary forces shape
organisms to optimize their survival and reproduction in the face of ecological challenges posed by the
environment Stearns 1992
a
...
Trade off:
i
...
maintenance vs reproduction
iii
...
current vs future reproduction
b
...

Static decision: doesn’t change like when to leave patch or prey to eat

...
Affected by time and state
...
make series of state dependent decisions
2
...
Reproductive value compares organisms: value in particular state is the
expected future number of offspring produced over remainder of lifetime
d
...
Size affects: metabolic rate/survival/intake rate/rate of reproduction
i
...
if big enough could get through winter on fat so could breed
...
Starvation predation: small birds in winter
1
...

3
...

costs to being fat: winter and cuthill 1993: starlings
a
...

ADAPTIVE FAT LEVELS: Predation increase with fat: trade off between growth and predation
...
Best LTS minimise starvation and predation but maximise survival
5
...

work back from time where relationship between currency and state is known
a
...

Foraging stochastic
...

Benefit of model: get daily routine of foraging and use same to find routine of singing vs foraging
6
...
Starvation likely: accept predation risk and mortality through predation
iii
...
Gosler 1995: sparrowhawk

...
Sparrowhawk declines in 70s and recovered: see changes in
great tit mass
a
...

Wrens rarely killed by sparrowhawk and saw no change in mass
iv
...
Early reproduction: shorter generation time, higher growth rate, survival to
maturity
2
...
Parental Care


...
Game theory: two parents feeding young, amount of food it gets depends on both parents but costs to parent
like effort/food given are paid by it individually
...
Males and females interact for care
i
...
Animal feeding alone: optimisation
...
Models generally work with single variable eg reproductive effort
...

Provide food, water heat
a
...

teach skills
2
...

Offspring do better: but benefits likely to decrease as they grow (diminishing returns)
a
...
saved effort of mate may be beneficial to you if you will breed with them again in the future like swans
3
...

Reduced locomotor performance: pregnant snakes/lizards, birds with eggs
a
...

time and energy costs

...
Engel 2016: burying beetles: hormone-mediated infertility via pheromones
in females in the time current brood needs care
...

iii
...
Origin of progressive provisioning parent: Ammophilia pubscens
(progressive) offspring survive better and if nest infested can decide
whether to desert to save energy
2
...

Food is scarce


...
EG albatross may desert
a
...
partner can rear young alone
...
conflict of interest between parents- both parents may benefit from deserting but benefit depends on the
partner staying and caring for young
3
...

Male

...

Female

...

McNamara and wolf 2015: 2 factors cause sex differences in care: certainty of parentage and sexual
selection
...
The coevolution of levels of care and the ability to care may be a
key factor underlying the evolution of sex differences in care
4
...

Trivers: conflict of interest between male and female
a
...
Evolutionarily stable strategy (caring vs
...

Cannot be ‘invaded’
a
...
2 parts to smith’s analysis
1
...
Finding stable outcome given pay offs
i
...
care
2
...
These decisions affect:
1
...
survival of eggs
3
...

Pay off matrix (current and future)

...
both care
2
...
female care, male desert
4
...
each pattern can be an ESS (depending on
environment and pay offs)
c
...
female cares: male does better by caring
i
...
Neither do better by changing behaviour
...

Criticisms of the model

...
males have chance of breeding again but
females dont
2
...
For internal consistency of the model:

...

Probability of remating on desertion depends on others behaviour
...

If all females caring, no mates so p=0
6
...

With partner: determines pay off from reproductive attempt under consideration
a
...
so maynard smiths model is only a game between male and female parents, in fact there is interaction with
rest of population because everyone else’s care or desert decision affects yours
iv
...
4 mating strategies within same population

...

polygyny (male, 2 female)
b
...

Polygynandry (2 male, 2 female)
2
...

long term study of dunnocks, complex social system can be explained in terms of selection on males
and females
...

How hard should individual work
b
...
each member prefers others to do work
...
Individual effort gives shared benefit but personal cost
...
conflict of interest as benefit depends on what
others do but you pay a cost contributing to
team effort
3
...

look for outcome at which neither male or female can gain from changing effort

...
Male

...

Maximises his LRS
...

when female decreases effort, he undercompensates: increase is less than partners decrease
...

c
...
Stable solution
1
...
What happens in trios?

...

if beta males paternity below a critical level wont help rear brood, but above and all 3 birds give food
to young
b
...
alpha vs beta males
1
...
female vs alpha male
1
...
alpha guards female and female sneaks away to copulate with beta
a
...
in typical ESS models, a response occurs over evolutionary time
i
...
In reality, individuals respond to differences in quality
1
...
But what if they can respond to each other and negotiate way to stable
solution?
iii
...
Final efforts emerge from negotiation during series of interactions
2
...

each partner can adjust their effort in response to the partner: negotiation
3
...
Subtle but crucial distinction:

...

2
...
undercompensation still occurs
v
...
Manipulate by:

...
Wright and Cuthill 1989
i
...
Partner compensates but not fully
a
...
socially monogamous bird species
...
Artificially elevated testosterone:
1
...

Partner removed

...
Review of studies in meta analysis
ii
...
Partial compensation for reduction in effort of mate
c
...

Sex differences in care

...
Birds of prey

...

female stay with young and prepare food
2
...

desert living
a
...
less time for foraging
i
...

males expenditure greatest during chick rearing

...

Costs of reproduction

...
future reproduction
1
...

distribution of major events over lifetime of individuals
a
...

not every trait can be adapted in isolation as trade offs occur
2
...
Lack clutch size
1
...
Trade off number of offspring against their success, to maximise
productivity

...

Typically observed clutch size is smaller than lack clutch size
3
...

ignores future reproductive success
a
...

parent reduce clutch size to avoid this
4
...

5
...


ii
...

A drop in egg viability alone does not favour small clutches when only a
single nesting attempt is possible
...
Predation
signals attract predation
...
Death and injury to males fighting

...
Internal costs to reproduction
1
...

work associated with attracting mates or caring reduces condition → mortality
...

EG Kestrel, polar bearh
iv
...
External costs
2
...

Breeding cycle takes over a year, affects condition
a
...

Black browed albatross

...
breeds every year
c
...
4kg, breeds first at 12 years
i
...
bigger cost of reproduction so bigger probability it wont breed next year
d
...
9
...
breeds every other year for same reason as grey head: physiological costs of reproduction too great to
replenish every year
e
...

Could have both internal and external working in tandem

...
annual variation in climate and food availability - Environmental Constraint hypothesis
ii
...
Measuring costs

...
measure current reproduction and future success in natural population
i
...
Effort is not a clear evidence of cost just a correlation
a
...
might get no variation
1
...
Pattern may reflect adaptive variation
1
...
good quality animals both survive better and
reproduce better as able to put more effort in
b
...
Artificial variation
...
best evidence for behaviour reasoning as need to see what happens when animal does something different
c
...
Daan 1996
i
...
manipulated brood size of 39, studied time of
death based on return of dead individuals by
public

...


2
...
Just drop dead not predation so directly
impacted future reproductive success

...

less effort for reduced brood as less to raise: increased reproductive success
ii
...
parasites
2
...

Costs of care in puffins

...
Experimental manipulation to understand the cost of reproduction
1
...
no extra food to control group

...

But! Fledgling success! Greater in experimental group
...
Conditions not great for puffins in years of experiment
1
...

Costs are rare?

...
reproductive trade offs only expected under food stress so costs might be rare
1
...
previously thought parental care represents high intensity work
1
...
Costs in
physiological costs
iii
...
intense activity is short lived
2
...
individuals might modulate costs
d
...
When in season should animal breed?
1
...
But young born earlier in year do better
...

Birds that lay early produce large clutches
a
...
So why dont all parents breed early?
1
...
Trade off:

...

but delay → lower success
b
...
High quality birds can lay sooner and produce larger clutch
...
Nilsson and Svensson 1996
5
...

delayed breeding by removing first clutch (2nd clutch laid week later) so had to feed later
a
...
second clutch to lay (female) compared to control experimental birds had higher energy expenditure
i
...
→ moult delayed
b
...
higher energy expenditure in winter
i
...
lower survival to next year
c
...

Trade off between reproductive effort and moulting effort
...
Poor feathers = poor insulation
e
...
Lack clutch size: most productive
1
...
Lack laying date: when most food
1
...
Each parent has different optimum according to own condition - state dependent decision
iii
...
Individual variation represents:
1
...
Consequence of underlying individual differences with each animal at own
optimum
v
...

vi
...
This allocation maximises overall egg viability (or minimises egg mortality)
...


11
...

Semelparity vs iteroparity

...
Marsupial mouse

...
Whilst females do it all year every year
2
...

return to spawning site to breed then die
i
...

1
...
EG pacific salmon, marsupial mouse males
3
...
Semelparity favoured if:

...

low probability of future reproduction
...
Iteroparity: several bouts of reproduction
1
...
Life History in Lobelias
1
...
2 species of mount kenya lobelias:

...


...
Semelparous: low probability of future reproduction
ii
...

Lobelia keniensis
...
Wetter habitat - Sits above tree line
i
...

Mutual breed of birds that pollinates both
c
...
suggests environmental factors affect which method uptaken
iv
...
Spider (Schneider and Lubin 1997)

...

Post hatching mother feed young, they then eat her
b
...
Doesnt need to be semelparous but chooses to be
i
...
Experiment: remove brood, measure value of care and success of second
brood

...
Hughes 2017: This study reviews the ecological and molecular evidence for the continuity and plasticity of
modes of parity—that is, the idea that annual-semelparous and perennial-iteroparous life histories are better
understood as endpoints along a continuum of possible strategies
...

a
...
Evolution of menopause: females lose reproductive ability but continue to live
1
...
Physiology
1
...
Why dont have more oocytes?

...
based on costs and benefits of reproduction after 45-50 years
i
...
Selected for so good as leave as it is
ii
...
Things that are adaptive arent always good as may have been adaptive at the time it was selected for but
in current day it is maladaptive
1
...
If it is adaptive, womans body may be designed by natural selection to survive with low oestrogen levels late in
life
1
...
Adaptive explanations:
1
...

advantage of stopping outweighs cost
i
...

high risk mom dies in
childbirth
a
...

look after dependent children
i
...

early models suggest benefits of stopping dont outweigh cost
i
...

ignores age related decline in
female survival and
reproduction
c
...

risk from death in childbirth
increases with age
i
...


Cant and Johnstone 2008: New Theory

large and benefits not as great
as reproducing yourself
i
...
Claim in humans
females disperse, new young
female joins group and marry
son of older resident female
...

Old female breed or help
younger and vice versa
...

New female not related to
offspring of older female but
older is to younger female
through son: her grandchildren
i
...

a
...
side effects of living for longer than we did in evolutionary environment (ageing)
i
...
modern hunter gatherers: first reproduce at 15
and 50% survive to 45
2
...
Conclusion isnt clear
ii
...
Hypothesised that
post-reproductive females act as repositories of ecological knowledge and thereby buffer kin against
environmental hardships
...
results show that post-reproductive females may boost the fitness of kin
through the transfer of ecological knowledge
...

old female lead groups in low salmon years - important because salmon abundance drives mortality
and reproduction
...

More likely to lead sons
b
...

b
...
Even under ideal conditions get increase in age specific death rates
i
...
Why does the body decay?
1
...

inevitable wear and tear EG teleomeres shortening etc
...
some organisms dont age
i
...
Evolutionary theories: ultimate explanations

...
no
...

How mutations accumulate

...
Medawar 1952
i
...
so discrimination between alternative is less strong
1
...
mutations that happen later in life under less
selection pressure so discrimination between

b
...
Antagonistic pleiotropy (Williams)

alternatives is less strong and mutations more
important early in life
1
...


3
...
Disposable soma (Kirkwood)

gene has multiple effects: if positive effect early
in life can counter big negative effect later in life
Frequency dependent: cost and benefit dont
need to be same size because if costs are larger
small chance will pay them and small benefit at
start of life means its passed on and selected for
Pays to have as it got you through early stages
...


even without senescence, will eventually
succumb to accident/predation
2
...

optimal level of investment in repair
...
level of repair vs LRS

...

X: lot input into repair, no energy into reproduction so may never have had energy to do it
...
Theory is complicated

...

High extrinsic mortality (independent of condition so accident and predation) → low optimal level of
maintenance
...

b
...

Opossums on predator free
islands age more slowly than
same species on mainland
...

Keller and Genoud: Queen
ants
...

Get surrounded by workers
and protected from predation
...
Eusocial
10 years, solitary 0
...

c
...
Fluctuating Asymmetry

1
...

Small random deviations from perfect symmetry in a trait which is normally (bilaterally) symmetrical

...
But if measure whole population find
instances where right is longer than left and vice versa
...
Directional Asymmetries
1
...
Antisymmetry
1
...
Why is FA interesting?

1
...

genotype, phenotype expressed from it, stress experienced and see deviations from ideal
development
2
...
The optimum is known

...
Absolute magnitude of FA (size asymmetry see compared to others in
population) is an assay of an individual’s ability to cope with
developmental stress

...
Causes of stress
1
...

Temperature

...
Relationship between FA values for number of wing morphological traits and developmental temperature
...
Temperature increases so
does FA (difference in left and right wing size)
a
...
Zakharov 1997: seals in Baltic
i
...

Population density

...
Fa higher in years when breeding density high
c
...
Moller 1992: swallows and mites: added blood sucking mites, untreated control or disinfected nest
i
...
Male FA affected but not female tails - suggested that sexually selected male
tail is susceptible to stress
ii
...
Tail on each side so compare FA
...

Dietary

...
Food deprivation during weeks undergoing moult, deprivation could be predictably in morning/afternoon or
unpredictably
...

ii
...
Genetic

...
Hoelzel 2002: northern elephant seal population crash
...
Left and right bones - sides similar before bottleneck and after high FA
a
...
Wilsey 1998: birch trees
i
...

new mutations of major effect

...
Evolved resistance due to single mutation
...
Development destabilised by new allele with big effects but a modifier evolved which re-stabilised
development and FA went down
c
...
De Coster 2013: 4 African Rainforest birds that underwent shifts in habitat quality
i
...
1 showed decreased (greenbull), other 3 showed increase
...
Increasing body size: higher taurus FA
iii
...
Selecting for genotype less able to cope with FA
v
...
Level but not direction of FA heritable

2
...
FA can tell you about good genes models of selection: Moller

...
Asymmetry = lot so indicates quality of
genes individual has
a
...
Are secondary sexual ornaments sensitive indicators?
i
...
also looked at wing feathers: not sexually
selected and FA not affected so secondary
sexual ornaments indicator of stress because
males affected by trait that was sexually
selected and not across whole body
2
...

Is symmetry itself assessed?

...
control I: captured and released
2
...
Manipulated FA on either side

...

Also fledged more young
b
...

Swaddle and Cuthill 1994: But flight is probably affected
i
...
Preferences in free chamber correlate with free
mating patterns
2
...
Swaddle and Cuthill 1994
1
...
Female attractiveness in humans
1
...
Symmetrical faces LESS attractive

...

Unattractive faces made more attractive by symmetry
3
...
But most are
fairly symmetrical so could symmetry be used as
cue to finding best mate?

...
Is symmetry preference a by-product of how we
learn categories?

...

Patterns in left bigger and right bigger forms
b
...
Publication Bias

...
As sample size increases, effect of
random variation reduces and so estimated effect homes in on true value

---