Chapters 9 - 14: Mate, Sexual Selection, and Parental Care Flashcards
1
Q
What is the origin of the female hyena’s psuedopenis?
A
- High levels of androstendione (T precursor) in males and females
- Higher T in pregnant females than lactating females
- Androgen blockers during pregnancy should halt masculinization of female clitoris
- Doesn’t significantly alter male or female embryo development
2
Q
How does dominance impact female hyena reproductive rate?
A
Their rate of reproduction is greatly increased by being a dominant rather than a subordinate female. This is b/c social status is passed by heredity in hyenas.
3
Q
What are the costs of the psuedopenis in hyenas?
A
- High death rate of first-time mother hyenas
2. High death rate of first litter of cubs
4
Q
What is the adaptive value of the pseudopenis?
A
- Pseudopenis development may be a by-product of selection for some other trait
- High androgen levels are adaptive → larger, more aggressive females
- Aggressive, high-status females leave more offspring; rank is inherited
- But androgens are not the clear cause of female pseudopenis development; don’t affect male offspring
5
Q
What is the social bonding hypothesis?
A
The pseudopenis may serve as a signal to reduce female-female aggression. (Kruuk)
6
Q
What is the sexual mimicry hypothesis?
A
By mimicking submissive males, females trick other females, and divert aggression. (Muller & Wrangham)
7
Q
How could pseudopenis development be adaptive?
A
- Females evolved to be dominant over males
- Males present erect penis as a submissive signal of courtship: no aggressive intent
- Females with a pseudopenis could signal lack of aggressive intent, submission, rank
- This would be a combination of social harmony and sexual mimicry hypotheses (Alcock)
8
Q
What is one example of a shifts in adaptive function?
A
Whistling moths both make and hear high-pitched sounds. Their ear is complex and has been assembled from parts that were evolutionarily for other purposes. The ear cells resemble mechanoreceptor cells involved in flight (for deaf moth species).
9
Q
What is the difference in biology between hearing and deaf moths?
A
- Deaf moths (Saturniids) lack ear with tympanic cavity of Noctuids
- B1 nerve in Saturniids carries info about the wing position
- B1 nerve in Noctuids carries acoustical info
- Similar structures, origins, but different function
10
Q
How are shift in adaptive functions defined?
A
“. . . A part that originally served one purpose becomes adapted by slow changes for widely different purposes . . .” - Darwin
11
Q
What is another example of a shift in adaptive function?
A
The varying structures of arthropod gills, all of which adapted from one ancestor with gills, leg appendages, and legs. This includes spiders, horsecrabs, crustaceans, insects, and myriapods. Function of these structures changed based on whether or not organism lived on land or water.
12
Q
How are water mites an example of sensory exploitation?
A
- Male mimics prey vibration (trembling stance)
- Female grabs him (prey), then releases
- Male deposits sperm packet, female picks it up and uses it
- Sensory exploitation: male exploits female’s pre-existing prey-detection system
13
Q
How are bowerbird calls an example of sensory exploitation?
A
Aggressive call deters rivals; this was its original function. Courtship call is a modified aggressive call and now a serves courtship role.
14
Q
How are guppies an example of mate preference and sensory exploitation?
A
- Females prefer males with orange spots
- Orange spots are the results of food (condition), not genetics
- Female mate preference may derive from pre-existing sensitivity for orange (nutrient-rich) foods
15
Q
What is the underlying assumption behind experiments on sensory exploitation?
A
If sensory exploitation is important in shaping effective signals, experimentation should reveal animal responses to totally new stimuli. Artificial attributes should elicit strong responses, particularly when they exaggerate the stimuli that should cause sensory exploitation.
16
Q
How was manipulation of the least auklet an example of sensory exploitation?
A
Model auklets manipulated with crests received the highest numbers of female solicitation displays.
- Experiments gave least auklets either a large head crest, a small head crest, or a breast crest. This was just feathers that protruded from those areas of the body.
- Auklets w/ a large crest on the head received the most courtship displays.
- This is b/c the crest causes sensory exploitation in female auklets.
17
Q
What is an example of signal receivers responding to an ancestral signal that is no longer present?
A
Scleroporus virgatus that lack blue stomach patch of other Scleroporus species will still respond to lizards with painted blue patches (by retreating).
18
Q
Can some animals have a preference for signals never possessed by the current or ancestral species?
A
- Present a novel trait not exhibited by any related species through experimentation.
- If there is a preference, then the preference is unlikely to be due to sensory bias.
- Sensory bias can develop is species are related, but this is probably not true if the trait has no shared evolutionary history.
19
Q
How are swordtails an example of sensory exploitation?
A
- Platyfish are closest relatives of swordtails, but lack swords
- Ancestor probably also lacked swords
- Female platyfish prefer males with experimentally elongated tails, even though ancestors never had them (pre-existing sensory bias)
20
Q
How is manipulation of finch and zebra finch white feathers an example of sensory exploitation?
A
Addition of white plume made male zebra finches more attractive to females. Females may be predisposed to favor white feathers b/c white feathers are used during nest construction.
21
Q
What is the panda principle?
A
Based on the panda thumb, which was retooled to function differently than its evolutionary purpose. Functional part is co-opted from previous parts; earlier structures used and modified for new purposes.
22
Q
What is Parthenogenesis?
A
A type of reproduction, occurring in some insects and flowers, in which the unfertilized ovum develops directly into a new individual.
23
Q
What animal does parthenogenesis occur in?
A
Whiptail lizards. Females have sexual behavior to stimulate parthenogenesis, but actually reproduce asexually. Sexual behavior just triggers reproduction.
24
Q
What features make yelling a recruitment signal?
A
- Single non-territorial, non-resident ravens call to attract other single ravens to prey
- Paired, territorial birds never call when they find prey in their territory
- By attracting other single birds, singleton is able to feed; cannot be repelled by territorial pair
25
What are some features of begging behavior as a signal?
1. Fitness cost of loud begging: attracts predators in some species
2. Other species under high predation have evolved quieter begging calls
3. Parents may give alarm calls that signal babies to be quiet
26
Why do some offspring beg louder than others?
- Sibling scramble competition: louder call gets the food
- Honest signaling: healthier chick begs more loudly, parents choose it over weaker chick. Parents can assess health of chick.
27
What is the definition of illegitimate signal receivers?
An animal that intercepts a signal from a different species to the detriment of the signaller and the intended receiver.
28
What is an example of illegitimate signal receiving?
Bat detects mating call of tungara frog, thus increasing predation risk. Male frogs often use just whine call (even though females prefer whine-chuck call) because bats hone in on whine-chuck call.
29
What are some examples of honest signalling?
1. Deep croaks deter rivals in European toads.
- Only large males can make deep croaks.
- Call is an honest signal of body size, and toad can decide whether to fight or retreat based on this signal
2. Threat duration and pushup frequency in side-blotched lizards will decrease after treadmill test
- Display performance accurately reflects physiological state
3. Only red deer in top condition can produce calls for long periods
- Call length is an honest signal of body condition
30
What are dishonest signals?
Receivers of honest signals can lose fitness by responding to dishonest signals by illegitimate signalers; aka signals that mimic a true signal to exploit the intended receiver of the dishonest signal.
31
What type of reproductive behavior do bowerbirds demonstrate?
- Males build elaborate display structures
- Females visit structures, evaluate them (and males)
- Male mates with female visitors who accept him; provides no parental care
32
What 2 bowerbird species don’t build bowers?
1. Ai. melanotis
| 2. Ai. crassirostris
33
What are the benefits of bowers in male bowerbirds?
1. Bower may signal info about male quality to female
2. Bower quality and decoration number is correlated to mating success
3. Bower may signal info about male health or parasite resistance to female
4. Bower may signal info about male’s developmental history
5. Better bower may signal better (larger) brain
This is important b/c most copulations are made by very few males, and female bowerbirds are choosy based on bower structure.
34
How do males differ from females in reproductive effort?
Sperm is cheap
Males have excess in gametes
Reproductive success depends on # of mates
35
How do females differ from males in reproductive effort?
Eggs are expensive and scarce
| Reproductive success depends on (limited by) number of eggs produced
36
What did Robert Trivers postulate about parental investment?
1. Time, energy, and risks taken to help offspring that may reduce chance a parent will reproduce successfully in the future
2. Tradeoffs between existing offspring survival vs. future offspring production
37
What role do females play in parental investment?
Generally make larger parental investment than males (per offspring)
- Gamete production
- Embryo development
- Lactation (mammals)
- Parental care
38
What reflects female fitness and reason to genetically prioritize parental investment?
Avoid costs of additional matings after choosing best partner (resources; good genes).
39
What reflects male fitness and reason to genetically not prioritize parental investment?
Compete with rivals (access to mates); evolutionarily, the goal is to mate with as many females as possible.
40
What factors influence sex role reversal?
- Female-biased operational sex ratio
| - Ability of females to produce too many eggs for a single mate to care for
41
What is sex role reversal?
Males provide parental care of offspring.
42
What are some examples of sex role reversal?
1. Seahorses carrying eggs in pouch to protect brood
2. Male Yellowhead Jawfish carrying eggs in its mouth to protect brood
3. Cichlid/severum male mouth-brooding for protection
43
How are Mormon crickets an example of sex role reversal?
1. Males present females with nuptial gift (edible spermatophore) that females use to provision eggs
2. Males mate once; females mate multiple times
3. When populations are large, male crickets are more choosy about who gets the packet (larger females produce more eggs)
44
What characteristics are there for sexual selection in evolution?
- Males and females differ in physical ornaments and display behaviors
- Males and females differ in reproductive success
- Costly traits that reduce survival will still be selected for if they increase lifetime reproductive success
45
What is true of sexual selection in baboons?
Dominance rank correlates w/ reproductive success.
1. Dominant and submissive males both mate equally, but dominant males mate more often when females are in estrus
2. Submissive males mate when females are not fertile
46
What is true of mate guarding/controlling in baboons?
1. Top-ranked male does not always have mating priority with estrous females
2. High-ranking males did not guard estrous females as long as thought
47
What features characterize a condition strategy of sexual selection?
- Males have a choice of mating tactics
- One tactic is usually superior to the other
- The males in poorer condition have to adopt the less successful tactic
- However, if their condition changes, so can their tactic
48
What are some alternative mating strategies in males?
1. Sneaker strategy - attempting to mate w/ females by having smaller bodies and feminized appearance to trick larger/dominant males
2. Satellite mating - indirectly mating w/ female by either being in physical proximity or taking advantage of mating opportunities after the dominant males have attempted to court
49
What are some examples of satellite mating?
- Male frogs attempting to fertilize eggs by trailing the female
- Rams following the dominant male in pursuit of a female or waiting to mate when the dominant male is distracted fighting off others and etc.
- Horseshoe crabs staying attached to females for long periods and taking advantage of the group for the opportunity to mate
50
What are some examples of alternative mating strategies that are under genetic control?
- In Sandpipers, can develop a territorial or submissive satellite strategy
- In sponge isopods, can be a large alpha, a beta who mimics female appearance, or a gamma which chooses a sneaker approach
51
What should happen if mating strategies are genetic?
They should have equal fitness irrespective of the strategy used.
52
What should happen if mating strategies are conditional?
Fitness should differ based on type of strategy.
53
In polygamous species, males can gain a fitness advantage over other males by what?
1. Removing sperm from previous male
2. Guarding females
3. Producing more sperm
4. Sealing female reproductive tract after mating
54
What is sperm competition?
Competition at the fertilization level.
55
What is an example of sperm competition?
In fish:
1. Territorial guards female; has more sperm
2. Sneakers sneak between males/females when territorials are spawning
3. Satellite males hover until fertilization between territorial/female, then slip in
56
How do damselflies address sperm competition?
- Damselfly males remove sperm from female before depositing their own sperm
- Special organ used for sperm removal
57
Can females cooperate in sperm removal?
Yes.
58
What is an example of this sperm removal cooperation in females?
In female dunnocks, males stimulate the female to remove sperm.
59
Can sperm competition occur within the female animal’s body?
Yes. Sperm can be stored in some species. Extra-pair copulations boost sperm numbers; overwhelm stored sperm by the previous donor.
60
What is mate guarding?
Male guards female after mating to prevent his sperm from being removed by another male.
61
What are the costs of mate guarding?
1. Time lost finding other mates
2. Fewer mates and fewer offspring
3. High energy expenditure guarding
62
What are the benefits of mate guarding?
1. Paternity assured
| 2. Fitness benefit?
63
What is an example of the effects mate guarding has on Seychelles birds?
- Male Seychelles warblers tricked to stop guarding
- Unguarded females quickly found new mates
- Extra pair copulations increased
- Male Seychelles warblers also adjust guarding behavior
- They spend more time guarding mates when more males are around
64
What affects extra pair copulations and mate guarding efficacy?
- Food availability affects EPC rates
- Food near nest makes females easier to guard
- Fewer extra pair copulations
65
How are honest signals one possible explanation for extreme sexual dimorphism in traits, coloration, and behavior between sexes?
May signal male quality. This is possible in peacocks:
- Plumage quality may signal male quality
- Carotenoids in food increase coloration: more carotenoids = brighter colors
- More carotenoids = better foraging/providing ability
- Carotenoids also involved in immune response: brighter = healthier; stronger immune response
66
What is the good parent theory in female mate choice?
- Females choose males based on their health and ability to be good parents
- Indicators of male parental quality:
1. Color
2. Ornamentation
3. Courtship behavior
- Female gets a healthy mate, no diseases/parasites
67
What is the Hamilton-Zuk hypothesis of parasite-mediated Sexual Selection?
1. Trait (plumage color) is related to an adaptive feature that is not obvious (genetically mediated parasite resistance)
2. Colors can only develop well if male is resistant to parasites
3. Resistance = good genes
68
What is the good genes theory in female mate choice?
1. Females choose males based on their ability to provide offspring with superior genes
2. Male courtship displays and ornaments or plumage quality signal info about genes
3. Offspring of such fathers would have survival and reproductive advantages
69
What is one example that may give support to the good genes theory?
- Singing duration in male starlings is correlated to immune response
- More singing stamina = stronger immune system
- Females prefer males with longer songs; offspring get genes for strong immune system
70
What is the runaway selection theory in female mate choice?
1. Females choose males based on their extreme plumage/coloration or display behavior
2. Genetically controlled female preference for a genetically controlled male trait
3. Male offspring of extreme fathers would be preferred by females and would have repro advantages; female offspring would inherit preference for extreme males
71
What is one possible example of runaway selection theory?
- In widowbirds, females prefer males with longer tails
| - Males with longer tails leave more long-tailed offspring
72
What is the sensory bias/chase away theory in female mate choice?
1. Females choose males based on displays/ornaments that exploit a pre-existing sensory bias
2. No benefit received by female
3. Males with elaborate displays/ornaments are favored, trait is passed onto offspring
73
What is monogamy?
Males and females pair for life; no other mates.
74
What is serial monogamy?
Males and females pair for breeding season; new mates chosen each season.
75
What is polygamy?
One male mates with multiple females; females typically only mate with one.
76
What is polyandry?
One female mates with many males; males typically mate with only one female.
77
What is the mate assistance hypothesis?
- Monogamy and male parental care are beneficial to offspring production (fitness)
- Fitness is actually higher in monogamous males than in polygamous males (e.g. seahorses)
78
What is the mate guarding hypothesis?
- Monogamy arose as a by-product of mate-guarding
- Males who guard fertilize more offspring than those who don’t (whose mates are fertilized by others), e.g. clown shrimp
79
What is female-enforced monogamy?
1. Females prevent males from seeking other males; keep them at home with the kids
2. Females attack males who stray
80
What is an example of dual-enforced monogamy? What does dual-enforced monogamy mean?
Mates of both sexes force the other mate to be monogamous.
1. Found in yellow-breasted chat
2. Mates are aggressive toward same-sex rivals
81
What do burying beetles do once they are no longer subject to female mate-enforcement?
They release sex pheromones to attract new mates at a very high rate.
82
Can monogamy be mutually beneficial to the female and male?
Yes. One example is in wrasses, where the male gains a large and fertile female, and the female gains an attentive male parent.
83
Is monogamy rare in mammals?
Yes. Less than 10% of mammals are monogamous.
84
Why is female parental investment in mammals larger than in that of other species?
Female mammals both lactate and have to wait a long time for gestation period to end.
85
What benefit do male Djungarian hamsters give their monogamous female mates?
They aid in the birthing process. This care results in better offspring survival rates.
86
What does male care cause in the California mouse?
Increased survival. Number of successful offspring declines if male help is not available.
87
What is shown in those prosimians that are monogamous?
1. In prosimians that travel (carry their young) instead of leaving young in a nest, males can protect against rival infanticide
2. Tight correlation between young-carrying and monogamy (prosimians only)
3. Correlation between monogamy and male parental care does not hold up for primate group as a whole
88
When do males tend to engage in monogamous pairing?
When females live far apart from other females. Leaving a territory for a new female would risk letting another male mate with first female (e.g., rock-haunting possum).
89
What mating behaviors do birds show in comparison to mammals?
Monogamy. Males provide help raising young, which reflects the mate assistance hypothesis.
90
What do we see in offspring/pairing behavior in snow buntings?
1. Female “widows” produce fewer young than paired females
| 2. Having both parents keeps egg temp. warmer → high hatching success
91
What effect does testosterone have in starlings?
Male starlings given testosterone are worse parents and show less offspring feeding behavior.
More testosterone = fewer fledglings
Less testosterone = more fledglings
92
What is not true of monogamous pairings in birds?
Social monogamy is not the same as genetic monogamy. Extra pair copulations is common, so birds engage in “cheating” behavior.
93
Monogamous males may help raise chicks that aren’t theirs. Why do birds do this?
1. Fitness cost: energy wasted helping non-offspring
2. Benefit: chance for EPC = higher fitness. Attractive males get more chances to mate, don’t have to raise all kids; avoid costs of monogamy. Other males are monogamous, bear costs of raising others’ kids, but may raise some of their own even without EPCs.
3. This reflects the role of female choice.
94
When does polyandry occur in birds?
1. One female has multiple male mates
2. Few territories available
3. Sex ratio highly skewed towards males
4. All males in group associated with female will breed; solos won’t
95
How does polyandry manifest in phalaropes?
- Females more brightly colored
- Female mates with male, then another, etc.
- Each male raises a clutch of eggs alone
96
How does polyandry manifest in female spotted sandpipers?
- Female fitness is increased when more offspring are produced
- More than 4 eggs per nest not possible: fewer chicks survive
- By multiple clutching, female fitness is maximized, while keeping nest size optimal: 4 eggs
97
Why do male spotted sandpipers accept polyandry?
1. Male-biased sex ratio
| 2. Abundant food for mates and chicks
98
How is chick care related to polyandry in spotted sandpipers?
1. Only one parent needed for chick care
2. Young are independent and can care for themselves: well-developed at hatching
3. Male deserters fail to hatch young; female deserters are able to raise young (via male care)
99
What are the genetic benefits of polyandry in birds?
- Fertility insurance: all eggs likely to be fertilized
- Good genes: EPC partners may be of higher genetic quality than monogamous partner
- Genetic compatibility: more mates increases chance of genetic match
100
What are the material benefits of polyandry in birds?
- More mates = more resources (food) or parental care
- Better protection: lower harassment rates
- Infanticide reduction: paternity confusion reduces chance of infanticide
101
What are the costs of polyandry (in primates)?
- More partners = higher risk of STDs
- More challenges to immune system
- Polyandrous primates have higher white blood cell counts than monogamous
102
How do cavies demonstrate some benefits of polyandry?
1. Females with 1 mate have lower fitness (fewer surviving offspring)
2. Females with multiple mates have more surviving offspring
103
What did EPCs cause in offspring birds?
Extra Pair Copulation offspring had better immune responses than Within Pair Young
104
What type of resources do females gain from polyandry?
More foraging opportunities
Spermatophores/nuptial gifts
Parental care
Infanticide protection
105
What are the variations of polygynous mating systems?
1. Female defense polygyny
2. Resource defense polygyny
3. Lek polygyny
4. Scramble competition
106
What is a female defense mating system?
1. When females occur in clusters, males will defend them against other male mating attempts
2. Females in groups = no monogamy
3. Very common
4. Male reproductive success increases as number of defensible females increases
5. More mates = more offspring
107
What is a resource defense mating system?
- Males control females by controlling access to feeding or nesting sites
- E.g., Male antlered flies compete for egg-laying sites
- Control site, and so control females
108
What is an example of a resource defense mating system?
1. Polyandrous female dunnocks forage over large areas
2. Supplement food → smaller territory size
3. Males were able to monopolize → female monogamy
109
What is a scramble competition mating system?
- Females are widely dispersed
- Resources are widely dispersed
- Males cannot control females or resources
- Cost of territoriality is higher than benefit
- Mating goes to first arrivals, or most persistent/durable
- Explosive breeding: reproduction happens in a short time and in localized site
a. Bigger/stronger doesn’t guarantee success
b. Race to be the first
110
How are 13-liners an example of this?
Scramble competition selects for spatial learning ability in 13-liners; male ground squirrel 13-liners will visit the sites of ovulating female much more often and search for them more in comparison to non-fertile females.
111
What is lek polygyny?
- Males cluster and form small display territories
- Females choose males; extreme skew in male mating success
- A few males get most copulations; others may get few or none
- E.g., Black grouse, sage grouse, MIs
112
What is the hotspot hypothesis?
- Females travel along certain routes
- Males concentrate along routes where females are
- One attempt to explain why lek polygyny forms
113
What is the hotshot hypothesis?
- Females choose from a group of males (grouping aids choice)
- Subordinate males congregate around more attractive males to have a chance at females drawn to hotshots
- One attempt to explain why lek polygyny forms
114
What is the black hole hypothesis?
- Females are mobile within habitat
- Mate with male who owns territory
- No female preference for lek size or particular male trait
- One attempt to explain why lek polygyny forms
115
How do black grouse support the hotshot hypothesis for lek polygyny over other hypotheses?
Top territory (most copulations) shifts over time
Territory location is not key
Females choose based on male attractiveness
116
How do marine iguanas support the hotshot hypothesis for lek polygyny?
Top territory (most copulations) shifts over time
Territory location is not key
Females choose based on male attractiveness
117
How do ruffs support the hotspot hypothesis for why lek polygyny forms over other hypotheses?
1. As more males come to lek, female encounter rate increases (then declines)
2. Males are attracting females to site
3. Above ~6 males, mating success for dominant male declines due to competition with other males
118
What are the costs and benefits of parental care?
Benefits:
- Offspring survival
Costs:
- Feeding/caring for young attracts predatory attention
- Adult mortality
- Offspring mortality
119
How does adult survival rate demonstrate this?
1. Northern species: shorter lives
2. Southern species: longer lives
3. Short lives: protect young
4. Long lives: protect self
120
What are some gender differences in parental care?
- Both males and females may care for offspring
- Females more likely to provide care than males
- Where both provide care, females usually provide more than males
121
What are examples of paternal care in fishes?
Jawfish:
Male cares for eggs
Mouth brooding
Limited to one brood at a time
```
Stickleback:
Nest aeration
Paternal care attracts females
Opportunity for multiple mates
Females add eggs to existing nest (“multiple broods”)
```
122
What happens during each evolutionary iteration of parental care?
Each increment of parental care is subject to selection.
123
What happens if cost exceed benefits of care?
If costs of care exceed benefits gained, females have no incentive to add additional care.
124
How do the costs of paternal care affect males?
1. Benefits of paternal care usually less than benefits of maternal care
2. Costs of paternal care usually higher for males than for females
3. Time spent on care = time not spent finding a mate
4. Potential for repro in males usually exceeds females → cost of care is greater for males
125
Why is parental care more expensive for females in the St. Peter’s fish?
1. Female caregivers take more time to recover body condition than non-caregivers
2. Fewer eggs in clutch following parental care clutch
3. Better body condition / larger body size = more eggs
4. Parental males spawn less frequently than non-parental males
126
Why do male water bugs do the majority of paternal care?
- Males brood eggs
- Eggs are large; require more O2 for development
- Large egg = low Surface Area/Volume ratio
- Eggs require aeration for oxygen; on male’s back kept moist
127
Why don’t the water bugs just lay smaller eggs?
- Instar molts limited (6)
- Larger larvae from larger eggs
- Larger larvae → larger adults
128
Why don’t female water bugs help w/ parental duties?
- Males with eggs attracts females (paternal care = attractive)
- Females need more resources (eggs expensive)
- Greater fitness cost for females than males
- Females who provide care would suffer loss of fitness in future reproductive episodes
129
What influences the ability to discriminate offspring?
Social cues among different but related species help prevent mistakes in offspring discrimination.
- Colonial species better at distinguishing offspring
- Solitary species worse
130
How do bluegills demonstrate offspring discrimination behaviors?
- Male bluegills aggressively defend young
- Expose to potential cuckold, aggression is reduced in egg defense but not fry defense
- Males can distinguish offspring (fry) by smell
131
How do male baboons demonstrate offspring discrimination behaviors?
Male baboons intervene more often on their own offspring’s behalf during altercations or when other males kidnap/threaten to engage in infanticide
132
What does offspring discrimination imply?
1. Parents should evolve recognition skills when chances of being exploited by other’s offspring is high
2. Should recognize strangers
3. Should reject non-kin; favor relatives
133
What are the costs of ignoring an adoptee?
1. Neglecting own offspring by mistake
2. Hurting/killing own offspring by mistake
3. Err on the side of caution—feed any chick that enters nest
4. Wasted time and food on stranger
5. Modest fitness cost to genetic offspring, but outweighs potential cost of chick rejection
134
What are some reasons that adoption among species might be useful to the adoptee?
- Small, underweight chicks may leave home
- If adopted, they survive, and gain more weight than they would if they stayed
- Avoid neglect, improve survival
135
What is the brown-headed cowbird an example of?
Brown-headed cowbird is a nest parasite of other birds. They lay eggs in nests of others, but don’t raise young.
136
How do brown-headed cowbird exploit begging and food acquisition behavior in their adopted parents?
1. Size bias in feeding: larger chicks get fed more
2. Brood parasite is larger than host chick
3. Advantage to parasite: adopted parents feed it
137
What is interesting about brood parasitism in cuckoos?
The shared ancestor had parental behavior, but migratory descendants developed obligate parasitism behavior.
138
Why are wood ducks parasitic?
- Nest sites (cavities) are scarce; competition over nests
- Successful parasite gets nest; eggs of loser may already be in it
- Successful parasite raises all chicks
139
How do widowbirds parasitize finches?
1. Widowbirds parasitize finches
2. Similarities between parasites/hosts in egg color, begging behavior
3. Possible sensory exploitation of ancestral host
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How did cross-fostering in blue and great tits demonstrate the costs of nest parasitism?
1. Blue tit (small) parent w/ great tit (large) offspring: offspring survived b/c it was larger and size is important
2. Great tit (large) parent with blue tit (small) offspring: offspring did poorly b/c the baby was small and size is important when raising young in great tits
141
Why do birds accept brood parasitism?
Accepting the egg may be adaptive if:
- Removal of parasite egg results in host egg ejection by parasite
- Removal of parasite egg results in nest destruction (mafia)
- Leaving parasite egg prevents loss of host eggs
- Parasitism occurs late in season: too late to try again
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What does the idea of an “evolutionary arms race” imply about natural selection and brood parasitism?
- Species in conflict
- Each exerts pressure on the other
- One evolves, the other responds
- Brood parasite/host relationships can also coevolve
143
How do egrets show parental favoritism?
1. Siblings fight, but parent doesn’t intervene
2. Strongest chick wins food (care) from parent
3. Weaker chick dies
4. In egrets, greater fitness cost if only raising one offspring (asynchronous brood)
144
How do brown boobies commit siblicide?
- Older chick ejects younger, smaller chick from the nest repeatedly
- Outside of nest, the parent ignores the other ejected chick
- Chick dies
145
How was this brown boobie siblicide behavior explored in the lab?
Cross-fostered masked (siblicidal) boobies in non-siblicidal blue- footed booby nests:
1. Masked booby parents tolerate siblicide
2. Blue-footed booby parents interfere and prevent siblicide
146
How is mouth-opening behavior in birds (i.e., gaping) an honest signal to parents?
Gape color affects amount of food nestling receives: more red = more food
Color as a signal of chick condition/health
147
What about the color of coots?
Coots w/ more orange coloring got more care b/c the color is a sensory exploitation they use that parents prefer.
148
What are some costs of sociality in animals?
1. Reproductive interference: females eject the eggs of nest mates
2. Mate competition
3. Cuckoldry
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How do fieldfares demonstrate other costs of sociality?
1. Competition for food
| 2. Larger colonies have lower rates of hatchling survival (starvation)
150
Are parasites a cost of group living?
Yes. Larger groups have more bodies → more parasites. Diseases and parasites can be easily transmitted. Parasites can negatively affect growth and survival.
151
What is the dilution effect?
Living in a group minimizes predation risk for individuals, but there are sometimes exceptions to this (e.g., bait balls).
152
What are some benefits of sociality?
1. Mutual defense: others come to your aid
2. Also true for Bluegills and Maomao fish
3. If there is an immediate return to both individuals, behavior is termed a mutualism
153
What is one example of cooperation among mate competitors (in blue birds)?
- Bright males permit dull males to nest nearby
- Intermediate males not permitted
- Dull males are less competitive with brights; bright male can get EPCs with dull males’ mates
- As such, dull and bright males cooperate
154
How do manakins display cooperation among mater competitors?
- Multi-male mating display in long-tailed manakins
- Only one male mates (alpha); Beta aids display, but doesn’t mate
- By cooperating, beta secures place in hierarchy; gets to be an alpha in the future
155
How do meerkats demonstrate reciprocity?
1. Help today at a cost to individual; receive help from another at some future time
2. Reciprocity predicts regular sentinel rotation
3. Personal safety hypothesis predicts sentinels are not at as much risk as it appears; they stay near retreat hole and are unlikely to die b/c of their position as sentinel
156
How is allogrooming a display of reciprocity?
Groomer aids “groomee” with no immediate benefit
| Grooming will be paid back later
157
What did they show experimentally w/ primates when getting food in the lab?
1. If the primate was paired w/ a partner who helped them get food when it was on their side, they were more helpful to the primate
2. If paired w/ a selfish partner who did not get them any food on their side, then they did not help their partner either
158
What does reciprocity imply?
Actor performs favor and is/expects to be repaid later for helpful act.
159
What does altruism imply?
Actor performs helpful behavior at personal fitness cost (lost reproductive opportunities, survival costs).
160
What do relatives get from altruistic behaviors?
1. Close relatives benefit, pass their genes on
| 2. Actor receives indirect benefit (some genes are passed on)
161
What is the coefficient of relatedness?
The probability that homologous alleles in 2 individuals are identical by descent. A way to measure how closely related individuals are to each other.
162
What is Hamilton’s rule?
An allele for altruistic behavior will spread if:
rbB > rc C :: benefits of act exceeds cost of act for relatives
```
B = extra relatives produced by altruist’s actions
rb = coefficient of relatedness between altruist and extra relatives
```
** Measured in # of offspring
163
When does altruistic behavior spread?
1. Cost to actor is low
2. Relatedness between altruist and beneficiary is high
3. Benefit to recipient is high
164
How is kin selection understood and what are its features?
- An individual increases its fitness by increasing the number of young (genome) that survives to the next generation
- An individual usually does this by increasing reproductive rate
- However, organisms also share genes with close relatives
- Therefore, helping your relatives also increases the success of your genome
165
What did Hamilton propose about kin selection?
1. Kin selection: investment in kin should be in proportion to the degree of relatedness
2. Relatedness = the probability of sharing genetic material (0.5 for full sibs; 0.25 for first cousins, etc.)
3. Fitness derived from survival of relatives = “inclusive fitness”
166
What is kin selection?
Kin selection = natural selection that favors the spread of alleles that increase indirect fitness.
167
What are the 2 components of fitness?
1. Direct fitness = # of your own offspring
| 2. Indirect fitness = # of offspring produced by your relatives that share some of your genes
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What are examples of evidence for kin selection?
1. Most social groups consist of related individuals, mostly siblings or first cousins
2. Most other cases of altruism – nest helpers, etc. are for parents or siblings
169
How is helping behavior in ground squirrels an example of kin selection and altruistic behavior?
- Helping behavior: alarm calls in ground squirrels
- Callers are killed at a higher rate than non-callers
- Calling behavior is not reciprocated → altruistic
- Calling more likely in females with close relatives nearby
- Personal risk is offset by increased survival of relatives (fitness)
170
How do birds demonstrated helping behavior by delivering food and care to offspring?
They give the food they find to offspring of their parents, and therefore increase their fitness by helping their brothers and sisters survive. The more related the helper, the more help they offer; secondary helpers give less help overall.
171
How do we know that helpers are good for offspring survival/indirect fitness based on experimental evidence?
When helped are removed, the average number of surviving offspring decreased dramatically.
172
How do bee eaters demonstrate conditional reproduction and exploit helping behaviors to increase fitness?
Female bee eaters can choose from the following strategies:
1. Scenario 1: female leaves natal site; pairs and nests; sits out breeding season; or lays eggs in another pair’s nest
2. Scenario 2: female stays with parents; sits out breeding season; helps rear siblings; helps and lays egg in another pair’s nest
173
How do frog tadpoles demonstrate kin recognition?
When engaging in cannibalism of their peers, they know not to eat other tadpoles that are genetically closely related to them.
174
What is eusociality?
- Special form of social organization
- Not everyone gets to reproduce
- Some are helpers all their lives
175
What characterizes eusociality?
1. Overlapping generations
2. Cooperative brood care
3. Castes: some non-reproductive individuals
4. Sometimes, extreme examples of altruism (e.g., soldier ants that kill themselves, along w/ bees that kill themselves to protect the hive)
176
How are bees an example of eusociality?
- Only queen reproduces
- Other colony members bring food to queen and fight enemies
- They may die b/c risk is high to protect queen
- Never get to reproduce themselves
177
What about naked mole rats?
- Similar to bees in social structure
- Only queen reproduces
- Other colony members bring food to queen and care for young
- May never get to reproduce themselves
- Highly inbred (related)
178
How do bees and wasps (Hymenoptera) demonstrate kin selection?
1. Only the queen gets to breed
2. All other individuals are (female) workers or males
3. Females are all sisters :: the result of fertilization of the queen by a haploid male
4. Females share 75% of their genetic material with their sisters
5. Females share only 25% with brothers
6. However, queens only share 50% of their genome with their own progeny
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What does this ratio of relatedness in bees and wasps cause?
Result: a large caste of non-breeding individuals that invest only in siblings
- Preferential investment in sister care vs. brother care
- Societies are female-dominated
- Females spread more genes by being helpful sisters than by being mothers
180
What is a powerful shaping force in human behavior?
Culture.
181
When do humans remember faces better?
If they are associated with generosity.
182
What does the field of sociobiology examine?
The evolutionary underpinnings of human social behavior.
183
What are the critiques of sociobiology?
1. Humans behave in ways outside of evolution: not everything is done to increase inclusive fitness.
2. Not all human behavior is adaptive.
3. Evolutionary approach to human behavior is based on inequality and is dangerous.
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What the responses to these critiques?
1. Brain is shaped by evolution; not every decision is.
2. Not every behavior needs to be adaptive; adaptationist approach creates testable hypotheses.
3. Sociobiology explains why certain behaviors have evolved; does not attempt to justify immoral behavior. Behaviors may be flexible and subject to change.
185
What is the indirect fitness hypothesis for adoption?
- In many societies, adoptive parents are actually related to adopted child
- Unrelated adopters may gain benefits from child (such as work)
- Small families more likely to adopt unrelated kids than large families b/c benefit is less needed
186
What is the side-effect hypothesis for adoption?
- When offspring are lost or parents are infertile, adoption of unrelated offspring is more likely
- Urge to adopt is a (maladaptive) manifestation of parental drive
187
What is predicted about male mate preference?
Prediction: men should prefer sexual cues associated with high fertility
1. Link between preferred female traits and estrogen (fertility)
2. Men prefer scent and face of ovulating women
188
What factors should female mate preference reflect?
1. Ability of men to supply good genes
2. Ability/willingness to care for offspring
Masculine faces may or may not be a reliable signal.
189
How does higher income reflect male reproductive success?
1. Number of potential conceptions (NPC) is correlated with (higher) income
2. Especially true for older men
190
What is an example of conditional mate preference?
- Women with high view of self attractiveness prefer more attractive men
- Prefer more “symmetrical” men than women who did not rate selves as highly attractive
- Male and female self-perception of attractiveness affects mate preferences
- Less attractive people settle for less attractive mates
191
How do one-night-stands show conditional mate preference?
- Men have lower standards for one- night stands than for long-term partners
- Men and women differ in standards for short-term partners
192
How is # of partners across the lifespan a demonstration of gender differences?
- Men and women differ in number of mates desired
- Women prefer fewer, men prefer more
- Men and women differ in likelihood of sex based on how well they know their partner
- Men more likely to have sex with someone they don’t know well
193
What is one indication that rape may be an alternative mating strategy?
Rape victims are more likely to be young and fertile.
194
What is some evidence that abortion may be employed adaptively?
Accidental Pregnancies: more likely to be aborted in younger women, but not in older women.
195
What are three examples of parental favoritism in humans?
1. The likelihood of paternal financial support is higher for related children than step children.
2. Child abuse more likely in household with a step-parent than in a household with 2 biological parents.
3. Parents more likely to leave money to male children. Males use wealth to gain mates, and thus leave more offspring.
