sexual conflict Flashcards
1
Q
The 2 sexes have different fitness maximising strategies over reproduction
A
Conflicting interests
2
Q
How do Argentine lake ducks have conflicting interests over reproduction
A
males have a corkscrew penis and female evolved anti-corkscrew vagina - very complex physiology to reduce change of unfavourable copulation
3
Q
How does sexual conflict begin
A
all starts with the mere existence of sexes
4
Q
definition of anisogamy
A
males produce many small gametes - sperm
females produce few but large gametes - ova
5
Q
CHECK why is there conflicting interests between males and females
A
if all males and all females are strictly monogamous over their full life = no sexual conflict
what is good for male is also good for female and vice versa
6
Q
what is ELRS
A
expected life-time reproductive success
7
Q
why is lifelong monogamy so rare
A
lifelong monogamy is unlikely due to some level of polygamy by one or both of the partners
female strategy - not put all their eggs in one basket
same with males
allowing individuals to reproduce later
8
Q
same number of females and males - will result in
A
mean reproductive success is the same - 1 male 1 female = 1 offspring (in humans on average)
if sex ratio is 1:1 - variance for females tend to be smaller
females are the limiting sex and are pursued by males
females are constrained by biological factors like gestation or parental care
males are only constrained by access to amtes
9
Q
polygamy definition
A
Polygamy refers to either one male mating with multiple females or one female mates with many males.
10
Q
types of sexual conflict - pre-zygotic
A
conflict over copulation eg duration of copulation, frequency of copulation
male/female harassment and coercion
paternity control
sexual cannibalism
11
Q
types of sexual conflict - post zygotic
A
infanticide
conflict between parents
genomic imprinting
12
Q
examples of conflict during copulation - penis
A
penis’ in many species are designed to discourage remating by females
- dagger like penis - bedbugs
- sclerotinised penis
- male fruitflies inject female with toxins (proteins ACp62F) in the ejaculate
13
Q
why do some males cause injury to females during copulation
A
causing injury during copulation preventing females from remating
14
Q
example of sexual harassment in nature
A
water striders - have specific appendages to grasp female
the interest of male is to transfer more sperm that needed for eggs, prevents remating with another
Garter snakes: males surround the female and try to copulate
females can drown in the sea of males
15
Q
how some females fight back from sexual harrassment
A
frogs pretend to be dead - leading the male to lose interest
16
Q
paternity control in nature
A
penises are designed in many species to remove the sperm deposited in female reproductive tract by previous males
17
Q
paternity control - females fighting back
A
female dragonfly has a spike prevents male from holding on indefinitely
18
Q
sexual cannibalism - example
A
praying mantis and black widow
females are larger than males in many invertebrates
the female often devours the male whilst he is transferring the sperm to her
diacous - two bodies for different sexes
female wants to secure the nutrients for the offspring while male wants to copulate
female takes head and tried to eat the male during copulation
19
Q
sexual cannibalism - males fighting back
A
males fight and pre-emptively tries to injure the female
20
Q
Conflict over sex roles - penis fencing
A
Hermaphroditic marine flatworms - penis fencing
focusing on sperm donation
the loser fertilises the eggs inside the body - becomes the female in this situation
21
Q
partner manipulation - example
A
in slugs -
during copulation , slugs shoot each other with love darts
love darts are laced with hormones and increase fertilisation success
some slugs stab its partner > 3000 times during 22 min of foreplay before copulation
22
Q
examples on conflict over maternal care
A
infanticide
males in several mammals kill the infants shortly after the overtake group of females
-> males speed up the reproduction of females
females has a shared interest in offspring as live in pride together
but males have no interest in previous offspring
hanuman langurs - female among many males, female went with the males to prevent infanticide
23
Q
conflict between parents - examples
A
caring for the young is often beneficial for both parents
but - each parent pays the cost of care individually
- best option is to leave care to the other parent
- conflict over parental care
males spend 2 weeks singing to attract female and building the hanging nest, soft and main function is to keep eggs that female lays
both contribute to parental care
24
Q
examples of conflict over parental care
A
stickle back fish - males provide care by fanning eggs but may abandon them early to seek new mates
poison frogs - males and females negotiate over tadpole transport ; if one parent provides less care, the other must compensate
25
example of sexual confluct - penduline tits
both males and females gain by mating with many partners
both sexes gain by finding new mates, but both sexes lose if their mate finds a new mate
26
what does reduced male care result in
Less female reproductive success
and
increased male reproductive success
27
reduced female care =
increased female reproductive success
and
male reproductive success
28
how many penduline tit offsprings die due to both parents abandoning them
30%
29
definition of intragenomic conflict
genes that function for their own good and retention to the detriment of other genes
30
genetic imprinting - definition
the differential expression of the same gene depending on whether the gene was inherited from one's mother or father
switching genes off by heavily methylating the DNA
31
what does genomic imprinting influence
imprinted genes should influence an offsprings growth rate when the offspring is nutritionally dependent on its mother
32
how does each parents genome expression influence the embryo
paternal genome expression = increase offspring size
maternal genome expression = decrease offspring size
33
why should genes that impact embryonic growth not be imprinted in oviparous taxa
because offspring cannot influence how much yolk their eggs receive
34
what is oviparous taxa
taxa that lays eggs rather than in the womb
the amount of yolk inherbited by the egg is determined when the egg comes out
35
what do paternally inherited genes not impact the mother in individuals in the oviparous taxa
paternally inherited genes for increased growth do not impact the mother as the egg has already been laid
36
genomic imprinting - two copies of paternal genes
could result in overgrowth of placental tissues
37
genomic imprinting - two copies from maternal genes
Ovarian teratoma - germ cell tumours
38
unbalanced imprinted genes from mother and father can result in....
psychotic disorders
39
paternal - brain function - example of disorder
low to high
mental retardation
kanner autism
asperger syndrome
severe kanner
autistic savantism
40
maternal brain function syndromes
low to high
negative symptom schizophrenia
major depression
positive symptom schizophrenia
bipolar disorder
psychotic savantism
41
SSD
sexual size dimorphism
42
how is SSD an implication of sexual conflict
sexual size dimorphism (SSD) arises from sexual conflict because males and females often have different reproductive strategies , leading to divergent selective pressures on body size.
males often benefit from large size - competition and control
females often benefit from larger size - fecundity and choice
43
how is speciation an implication of sexual conflict
sexual conflict promotes speciation by driving rapid male-female trait divergence, leading to reproductive isolation through
- antagonistic coevolution
-genital mismatches
- divergent mating preferences
- hybridization costs
44
how does sexual conflict lead to extinction
sexually selected traits may enhance extinctions
45
example of sexually selected traits leading to extinction
large antlers of elk led to extinction
46
sexual conflict definition
the interests of males and females are often antagonistic over reproduction
47
when does sexual conflict occur
it can occur before or after fertilisation
48
examples of evolutionary arms races between males and females as a result of adaptations enhancing reproductive successes of males and/or females
traumatic insemination - bed bugs
toxic seminal fluid - fruit flies
sexual cannibalism - spiders and mantises
forced copulation and reproductive tract complexity - ducks
genital spines - seed beetles
sperm competition and cryptic female choice
49
organismal diversity
refers to the vast variety of life forms on earth, shaped by evolution, ecological interactions and genetic variation
encompasses - morphological, physiological, behavioural and genetic differences among organisms across different taxonomic groups
50
define the life history theory
a framework that explains how organisms allocate resources to growth , reproduction and survival throughout their lifespan
high reproductive rates environments have:
unstable habitats
high offspring numbers
small offspring size
little parental care
short lifespan
high survival rates environments have:
stable habitat
few offspring
large offspring size
extensive parental care
long lifespan
51
why does conflict arise between males and females during reproduction
- they face different costs of reproduction (starting with anisogamy)
- they face different future breeding possibilities (mortalities differ, adult sex ratios may differ)
- are more related to their offspring than they are to their mate
- may be subject to differing selection pressures (sexual and natural)
52
how do the life expectancies of females and males differ : mammals vs birds
mammals: females live longer
birds : males live longer
53
intralocus sexual conflict - definitions
the fittest allele at a given locus may be different for males and females
A single gene has opposite fitness effects in males and females (eg body size genes that benefit one sex but harm the other)
54
interlocus sexual conflict - definition
conflict occurs between different loci in males and females (eg coercion vs resistance)
interlocus sexual conflict occurs when alleles at different genetic loci in males and females have opposing fitness effects - leading to an evolutionary arms race between the sexes
55
intra-locus sexual conflict - example in humans
females - wider hip width - child bearing and birth
males : narrow hip adapted better for fast and efficient walking
56
what can sex * genotype interaction for fitness lead to
- trade offs in mean phenotype values
-maintenance of polymorphism in a population
— high frequencies of low-fitness alleles
— the evolution of sex-specific gene expression and/or new sex determination mechanisms (cichlids)
57
Intralocus antagonism - graph examples
no conflict = ordinary bell curve
unresolved conflict = grey bell curve and dotted line male and female fitness surface. female = male
partially resolved conflict = selection starts pushing sexes apart in selection. two grey bell curves (smaller) for female and male - middles overlap. two larger fitness curves.
fully resolved conflict = two seperate grey (trait distribution) and larger fitness surface with still overlapping - alelle in female is expressed, other allele is expressed in male
58
genetic architecture
underlying genetic basis of a trait, including the number, type and interaction of genes that influence its expression
encompasses:
1. number of genes involved
2. type of genetic effects
3. heritability
4. genomic distribution
5. regulatory elements
59
intralocus - definition
conflict is in one locus = between two alleles
60
Detecting intralocus sexually antagonistic selection (SAS) - example
serin - small passerine bird:
infemales - directional selection for increased bill width but decreased bill *depth*- indication of how strong the beak is eg in darwins finches
in males : no selection on bill width but stablilizing selection on bill depth
61
why does selection act differently on male and female bill shape ?
ecology of sexes may differ
sexual selection influences bill shape in males and/or females
62
rules of intralocus Sexually antagonistic selection - juneviles to adults
n juveniles, the alleles may have neutral or variable effects, but in adults, a gene that enhances female fitness (e.g., increasing fecundity) may reduce male fitness (e.g., by lowering competitive ability). This results from sex-genotype interactions, where selection pressures differ between sexes due to their distinct reproductive roles.
eg male red deer with relatively high fitness fathered daughters with relatively low fitness
63
interlocus vs intralocus sexual conflic
intralocus: (same allele/same locus) Occurs when selection coefficients have negative correlation in the same allele when expressed in males vs females
Sex-specific selection at a locus in one sex interferes with adaptation at the same locus in the other sex
interlocus: Occurs when males and females undergo different selective pressures at different loci
Produces adaptation and counter-adaptation that involve different loci
64
interlocus sexual conflict - selection pressures
selection pressures have genetic basis at different parts of the genome
may favour the male by harming females
expected responde in females is to counter adapt - leading to resistance
65
Interlocus antagonism - example - drosophila
foregin material in body = immune response = survival decreases
Insemination reaction mass in some Drosophila
- reaction by the female to seminal fluid
- swelling of the vagina to 3-4 x normal size
- resembles immunological reaction
accessory gland proteins (Acps) in fruit flies Drosophila
66
How are drosophila Acps involved in interlocus antagonism
Acps - increases male reproductive success, but decreases female lifespan
Accessory gland proteins (Acps) in fruit flies Drosophila
Male ejaculate contains proteins that influence female behaviour and physiology
Drosophila melanogaster has at least 80 Acps
Acps increase female’s egg laying rate, decreasing her likelihood of remating, incapacitate rival sperm
67
dN/dS ratio
non-synonymous vs synonymous mutation ratio
68
interlocus conflict leads to
sexually antagonistic coevolution AKA a coevolutionary arms race
69
what does a coevolutionary arms race select for?
males and females to
a) exploit each other
b) but also defend against exploitation
70
Interlocus sexual conflict in water striders
- males pursue copulations as much as they can
- females avoid copulations as much as they can
71
what traits are favoured in males?
persistence and copulation success
72
what traits are favoured in females?
resistance and the reduction of copulation rate
73
Interlocus sexual conflict in water striders
water striders have quantified persistent traits - morphological adaptations
- male grip and female resistance spike
as male persistence increases, female resistance also increases
74
explain the relationship between copulation duration and mating copetition outcomes in Drosophila
males win - copulation lasts longer - enhancing reproductive success
females win - copulation is shorter suggesting female resistance to prolonged mating
this reflects sexual conflict over mating duration
75
Interlocus sexual conflict - male manipulation
males try to manipulate females into investing more in the offspring sired by him
these males have a selective advantage
76
how does male manipulation impact female fitness
can lead to reduced overall fitness in the female
77
how do females respond during interlocus sexual conflict
females that can defend herself against such male manipulation has a selective advantage
78
how does the female response to interlocus sexual conflict impact males
females defence can have negative effects on the fitness of their mate
79
How does sexual conflict influence mating rate
conflict over the optimal mating rate selects males to mate more often than females
80
what are key conflicting optimal investments in reproduction
current vs future reproduction
eg : egg laying rate or brood-care investment
81
explain how females can control the usage of sperm and resulting paternity
females are selected to choose the sperm they use for fertilisation
82
percentage of homosexuality in humans
10/11%
83
What paradox does homosexuality fit into?
Darwinian paradox - 100% homosexual individual does not directly produce offspring
84
sexually antagonistic selection - SAS in humans : male homosexuality - twin studies
These twin studies showed clear evidence that there is a considerable genetic component to male homosexuality
85
a hypothesis on male homosexuality sexually antagonistic selection
when alleles favour many offspring in females - these same alleles in males favour homosexual behaviour
maternal relatives of homosexual men have higher fecundity than do maternal relatives of heterosexual men
86
Bullet points of intralocus sexual conflict
Sexually antagonistic selection
Polymorphism
Low fitness alleles
SAS & male homosexuality
87
interlocus sexual conflict
Sexually antagonistic coevolution
Accelerate rates of evolution
Selection for
- persistency in males
- resistance in females
88
Runaway sexual selection definition
positive feedback process
where a trait becomes exaggerated because it is preferred by the opposite sex, even if it has no direct survival benefit
over generations - preference for the trait and the trait itself co-evolves, leading to potentially extreme forms
89
example of runaway sexual selection
Argentine lake duck - males have extremely large penises
90
Female choice in wolf spiders
female spiders has large choppers that males have to go through in order to copulate
females can choose to either fight back - and slice the males head off
or allow copulation
deciding whether the male is father or food
91
why are there two sexes
small gametes - males
large gametes - females
92
define the SAX-ROSE framework
S- sexual selection: competition for mates and traits that increase reproductive success
A- anisogamy : differences in gamete size between sexes (eg large eggs, small sperm) influencing mating behaviour
X- xenogamy: outbreeding or mate selection strategies that prevent inbreeding
R- reproductive effort: investment in producing and raising offspring
O- Operational sex ratio (OSR): the ratio of sexually available males to females, affecting competition
S- Sexual conflict: evolutionary battles between male and female reproductive interests
E- Ecological factors: Environmental influences on mating behaviour , like food availability or predation risk
this framework integrates key evolutionary and ecological principles to explain diverse reproductive strategies across species
93
Reproduction is a what type of strategy?
Sex is an evolutionarily stable strategy (ESS)
94
How do smaller gametes arise
Ancestral state - equal-sized gametes fuse
mutant produces a smaller gamete
the gamete is half the size
this doubles the amount of gametes
resulting in higher reproductive success
pass on their genes more effectively
94
examples of game theory in reproductive behaviour
Evolutionarily Stable Strategies (ESS)
Hawk Dove Game
Prisoners Dilemma
Sexual Conflict
95
Will the mutant producing smaller gametes be selected for?
Model of Maynard Smith assumes that small gametes are half size and the mutant can make twice as many.
Selection will occur: if the survival of a smaller embryo is more than 50% more likely than that of a normal embryo
selection will not occur: if the survival of a smaller embryo is less than 50% likely than that of a normal embryo
96
What is an "invasion condition" during fertilisation
a rare mutant small gamete in a population meets large gametes
97
What is the marginal value therom?
The mutant producing smaller gametes win
A half size gamete fusing with a normal gamete results in an embryo 75% the normal size with survival at point B
But making twice as many half size gametes gives more surviving offspring since 2xb is larger than a
98
The origin of gamete sizes
Smaller gametes can be at an advantage
- two sexes evolve into a sexually reproducing population in which there was initially only one sex
- the small gametes evolve the ability to avoid fusing with each other
- the evolution of two distinct mating types: males and females
99
Gamete sizes of humans
sperm = 50 um
ovum = 120um
100
Ostrich gamete size
sperm = 69.6 um
ovum = 15 cm
101
Typical sex roles: who defined them and explained
Angus Bateman and Robert Trivers:
Typical male and female sex roles are due to sex differences in investment in individual offspring (parental investment theory)
Males: invest little into each offspring - can potentially have a large number of offspring - can greatly increase fitness by having multiple partners - rarely can increase fitness by being choosy
Females: invest a lot (more than males) in each offspring - cannot, potentially , have large number of offspring - cannot greatly increase fitness by having multiple partners
Batemans principle:
mating with drosophila
male success depends on his access to mates - increasing if given unlimted mates
females are limited to their egg production
102
Key differences between males and females
differences in gamete size
differences in other forms of parental investment
differences in resources donated directly to mates
103
Eager males and choosy females selection leads to---
number of fertilisable females <<< number of sexually active males = male biased operational sex-ratio (OSR)
104
mating decisions for females and males
males should frequently aim to mate with females even though the females may not benefit from multiple matings
females should be choosy and reject low-quality males
105
Example of male coercive sex
Bed bugs:
Traumatic insemination
- male bedbugs have a saber -like penis
- inserts directly into the abdomen of females prior to infecting them with sperm
- evolved to possibly overcome female choosiness
- females evolve a spermalege - modified region of abdomen where males pierces the female
Sharks:
males bite female sharks during copulation
therefore female sharks have evolved much thicker skin to protect themselves
106
explain the sex-role syndrome
1) sexual selection is stronger in males than in females, which must, be rooted in anisogamy
2) stronger sexual selection on males translates to female biased parental care
3) and male biased elaboration of traits
107
Behavioural traits that are expressed consistently are called...
Behavioural syndromes
108
Concorde fallacy
Past investment should not direct future actions
This disrupts the logic applied to "typical sex roles" - leading one to believe they may be false
109
What is Trivers Typical sex role theory/idea
females are more choosy than males because they invest more in the offspring - and so are limited in the number of offspring by how much they can invest
110
If Trivers Typical sex roles are correct - what would you predict for males with high investment in their offspring?
one would predict a sex role reversal
- male reproductive output would become more limited (compared to females)
- male provides a costly nuptial gift to the female - provides costly parental care to young
111
Pipefish - sex roles
males get "pregnant" and provide oxygen and nutrients to a clutch of eggs
females produce more eggs than males can look after (enough to fill 2 male pouches)
so
sex role reversal
female competition and male choice
112
A reason for sex role reversal
Spermatophores
,ales present a courtship gift - the spermatophore - limited in number so a valuable resource -
females eat the spermatophore - which is nutritionally dense - and are fertilised in the process
113
How would an increased ability to produce a spermatophore nuptial gift influence the katydid sex roles
If the valuable nuptial gift became more readily available - male competition would increase
flipping the sex roles again
this highlights that resources availability can flip the population's roles - conventional or reversed
114
Mormon crickets - sex roles
- males transfer an enormous edible spermatophore to females when they mate as a nuptial gift
- spermatophore may constitute 25% of male's body mass - mating only once
- female can produce several egg clutches - as long as they can persuade several males to mate with them
- males provide more resources so the operational sex ratio is female biased - more females looking for males than vice versa
female competition and male choice
male choice prefers large females - more fecund
115
Sex determination in mammals and birds
Fixed sexes
117
Sex determinants in vertebrates
three main types of sex determinant systems
- genetic sex determinants - x2
- environments sex determinant
118
Ancestral autosomes for sex determination - alligators and marine turtles
Temperature dependent sex determination (TSD) rather than chromosomal sex determination
119
Divergence into proto- sex chromosomes
Proto- XY system - lineage led to male heterogametic sex determination
Proto- ZW system - lineage resulted in female heterogametic (ZZ/ZW) sex determination
120
Taxa with an XY system
Frogs
Fish
Mammals
121
Taxa with ZW system
other frogs
reptiles - pythons, colubrid snakes, vipers
Birds
122
Chromosome differentiation evolution
sex chromosomes evolved by losing or gaining genetic material - leading to the differences observed in modern species
some lineages have undergone significant degeneration of the Y or W chromosome
123
Turtles sex determination
low temp - 100% males
high temp - 100% females
124
example of environmental sex determination
In clown fish the dominant individual in a pair becomes female - while the other is a male
In Bluehead wrasses the dominant individual becomes male - the other becomes female
in the marine worm Bonellia viridis larvae becomes males if they contact with a female and becomes females if they never come into contact with another female / first encounter a male
125
Sex determination system - complications
- highly variable systems (genetic SD and temperature dependent SD)
- Closely related species may have different sex determining systems
- some species can flip flop between different chromosomal systems (japanese frog = XY and ZW)
and
some species flip flop between temperature dependent and genetic sex determination (bearded dragons)
126
Sex allocation - species perspective
"good for the species"
sex allocation strategies vary across species depending on reproductive systems, environmental factors, and evolutionary pressures
while some species follow fixed sex ratios others adjust sex allocation adaptively to maximize fitness
127
sex allocation - individual perspective
produce always the rarer sex
- the stable offspring sex ratio is typically 1:1
128
Rarer sex - estimated lifetime reproductive success
the rarer sex will have higher reproductive success - this is frequency dependent variance / sex allocation
the rarer sex will gain an advantage in reproductive
129
Fisher's theory on frequency dependent sex allocation - 1:3
example:
1M:3F
the male on average has 3x higher reproductive success than a female
if a son costs the same as a daughter - a mother should produce sons - positive selection on mothers to produce sons
if genes producing sons spread in the population - the sex ratio becomes less female biased
when the population reaches 1:1 sex ratio - should be an equilibrium
130
Several type of sex ratios (SRs)
Conception: primary SR
Birth: Secondary SR
maturation
Adults: Tertiary SR
Post-reproduction : Quaternary SR
131
Sex ratio adjustment - Woodchuck.
Effect name
experiment - removal of females in a population
result - mothers over produced females
Returning soldier effect:
Birth sex ratio shifted towards boys after WW1 and WW2
132
Can parents influence the sex of their offspring?
Haplo-diploid animals can manipulate sex ratios by choosing to fertilise their eggs
- fertilised egg -> female
- unfertilized egg -> male
133
Chromosomal sex determination - mammals - male influence
differential production of X and Y bearing sperms
134
chromosomal sex determination - mammals - both sexes
Differential motolity (or mortality) of sperm affecting the rate of fertilisation
135
Chromosomal sex determination - mammals - female influence
differential implantation or survival of male and female zygotes
136
Maternal condition - Trivers and Willard model - TWM
1973
if the condition of mother affects the reproductive success of offspring to different degrees
mothers are expected to shift ratio of their offspring
Mothers in good conditions are expected to produce more sons
137
Testing the Trivers and Willard 1973 in red deer
- lifetime reproductive success(LRS) of sons related to rank of their mother
LRS of daughters is unrelated to rank of their mother
- high ranking mothers produced more sons
138
Dominant or suboordinate mother:
D mother = boys will be dominanat in the herd
S mother = boys will be subordinate
139
Issues with tests of TWM
non consistent pattern to support the TWM in ungulates
140
Critics of TWM - alternative explanations
- maternal age: older females may produce sons ie their last chance and they may be in good condition but these are not casually related
- parity : (no. of children born to a female): later born offspring tend to be daughter -> if low ranking females give births more often then this shifts their overall sex ratio
- subordinate mothers maybe more likely abort male foetuses than female ones
- the reproductive success of daughters may depend more strongly on the rank/condition of her mother than the RS of son - baboons; the daughter inherits the social rank of her mother
141
Mate attractiveness impact on sex ratio
Females may adjust the sex ratio of their offspring in response to attractiveness of their mate
142
Zebra Finches - mate attractiveness experiment
Burley 1986
mate attractiveness can be experimentally manipulated
- red colour ring -> attractive male
- green colour ring -> unattractive male
female who mated with:
- more attractive males - male biased offspring
- less attractive males had unbiased offspring
143
Seasonal variation in the environment
- sons produced early in the season may have better chances of breeding in their first year eg kestrels
suggests seasonal selection on sex ratios - favouring males in early broods
Why favour sons early in the season:
- males have higher chance of finding mates and reproducing when they mature
- early season conditions (food availability , competition) may favour male survival and fitness
why shift towards females later?
- later in the season , males may face higher competition or lower survival rates
- females may have better survival chances or contribute more to population stability
144
Helpers at the nest - sharing parental care - Warbler
Natural History of Seychelles warbler
- females lay only 1 egg in each nest
- daughters remain on the parents territory and help them to raise young (helpers)
- some territories have poor food resources , whereas others are rich
Helpers increase Reproductive success of parents on high quality territories BUT not on low quality territories
145
True or false : sexual selection and natural selection sometimes oppose one another
True
146
True or false: sexual selection can explain the existence of traits which appear to be maladaptive
True
147
true or false: the physical environment can mediate the strength of sexual selection
True
148
true or false: sexual selection can act on both male and female traits
true
149
definition : harem polygyny
mating system where a single male defends a group of females for the purpose of securing multiple mating.
150
Definition - lifetime monogamy
mating system in which an individual has only one mate at a time or throughout their lifetime
151
Definition: Polygyny
one male mating with multiple females
females mate with only one male
152
Definition: promiscuous mating
both sexes have multiple mates throughout their lifetime
153
Definition - sequential polyandry
female mates with multiple males in a series of temporally separate events
154
what is meant by sex genotype interaction
the fitness of a given allele depends on the sex of the individual carrying it
154
Parental conflict hypothesis - sex specific genomic imprinting
- There should be antagonistic coevolution between growth-enhancing and growth-suppressing genes
- Growth enhancers should be maternally imprinted, growth suppressors should be paternally
imprinted
155
Empirical tests of the Trivers-Willard (1973) model of sex allocation in ungulates
…produced mixed results, since in some species high ranking (and/or good condition) mothers
produced more sons whereas in other species they did not
156
sexual conflict over care...
may reduce the lifetime reproductive success of both parents
157
ASR
Adult sex ratio - may change over the life-time of organisms
159
how does adult sex ratios range over the lifetime of humans
Early life - biased ratio towards males
later in life - the ratio shifts towards females
160
in the 9th century the sex ratio for first born child was skewed massively towards boys... why?
0.76 - 3x more boys than girls
daughters were murdered as they were not desirable
161
what is the best ASR for the society?
too many men: violence problem
too many women: sexually transmitted diseases
in female biased populations - males have the upper hand - males can choose who they want
162
the influence of sex ratio on sex roles
sex roles can be flexible
in the two spotted goby - sex ratios shift over the breeding season
start of the season - male biased operational sex ratio (OSR)
later in the season : female biased OSR - slower rate
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adult sex ratio vs operational sex ratio
courtship behaviour of the male golby declines whereas the courtship behaviour of the female increases
early in the season - males have to compete - intense courtship early in the season
season went on - more death - more sexual activity - intense courtship early in the season
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female biased and male biased - adult sex ratio could lead to
Female biased adult sex ratio
Male polygamy
Female care
male biased adult sex ratio
female polygamy
male care
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sexual selection for large size - male to male
large male size is advantageous
- male to male competition : in fights over females and forced copulations
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how does body size change depending on sexual partnerships
monogamous - more equal size between mates
polygamous - more variance in sexual size dimorphism
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sexual selection for small size
- small males are more agile than large ones
- small males are preferred by females - agility of male displays of courtships
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Natural selection : division of resources
- males and females can reduce/ avoid competition if they feed on different resources
- huia , an extinct New Zealand bird
- females - nectarivorous
- male - insectivorous
this is a niche division
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Rensch's rule
across species, many animals exhibit a relationship between the degree of SSD and body size
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what may explain the Rensch's rule?
Rensch's rule is predicted by sexual selection in shorebirds:
- intensity of male-male competition
- agility of males' display
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How does SSD emerge in population?
1. male and female offspring have different growth rates
2. one sex grows for longer than the other, although the growth rates are the same
3. differential mortality of small and large animals
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what are the three major selection processes that influence body size
sexual selection
natural selection
fertility selection
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what is a Lekking?
a mating system where males gather in a specific area (lek) to display for females
females choose mate based on appearance or behaviour
males have no resources
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