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Organismal-Behavior Flashcards

1
Q

Tinbergen’s four ‘why’ questions

A

To determine WHY a behavior occurs, determine the:
1) Causation: What is the immediate cause of the behavior? (proximate)
2) Development or ontogeny: How has this behavior developed? (proximate)
3) Adaptive advantage or function: What makes this behavior beneficial? (ultimate)
4) Evolutionary history or phylogeny: How did this behavior arise in evolutionary history? (ultimate)
Behavior p. 2

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2
Q

Applications of Tinbergen’s ‘why’

A

1) Starlings sing because increasing length of day triggers hormones/air flows through vocal apparatus (causation), because they have learned songs from their parents and neighbors and have a predisposition to learn the song of their own species (development/ontogeny), to attract mates for breeding as singing increases reproductive success (adaptive advantage), because the most primitive living birds make very simple sounds, so it is reasonable to assume that the complex songs of starlings and other song birds have evolved from simple ancestral calls (Evolutionary history/phylogeny)
2) Sperm whales produce codas by pushing air past phonic lips in the nasal complex (causation) and they learn coda patterns from other whales through social learning (development/ontogeny), these codas allow recognition between and amongst clans (adaptive advantage), and this likely evolved from the use of echolocation in odontocetes to produce clicks similar to codas (Evolutionary history/phylogeny).
Behavior p. 2

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3
Q

Proximate

A

Causal and developmental factors of behavior

Behavior p. 2

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4
Q

Ultimate

A

Why and how the individual has evolved behavior

Behavior p. 2

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5
Q

Causal explanations of behavior

A

1) Concerned with mechanisms
2) E.g. Female lions are synchronous in oestrus because of chemical cues and take-overs by males
3) E.g. young die when new males take over pride because of abortion and infanticide or eviction
Behavior p. 5

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6
Q

Function explanations of behavior

A

1) Concerned with why mechanisms are favored by natural selection
2) 2) E.g. Female lions are synchronous in oestrus because this increases cub survival, young males survive better and have greater reproductive success when they leave pride in a group
3) E.g. young die when new males take over pride because females come into oestrus more quickly when cub is killed and males remove older cubs that may compete with his young
Behavior p. 5

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7
Q

How to show that behavior has a genetic basis?

A

1) In order for behavior to be adaptive, behavior must be heritable
2) In drosophila, different individual foraging behavior (between rovers and sitters) are caused by differences in alleles of the for gene. In honeybees, switch in behavior within individuals is caused by changes in for gene expression. So if gene acts similarly across taxa, it likely is heritable?
3) Blackcaps in Germany are highly migratory, but in Canary Islands are sedentary. When breeding these two populations, offspring showed intermediate migratory restlessness, indicating genetic control.
Behavior p. 8-9

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8
Q

Wynne-Edwards model of group selection

A

1) Idea that behavior serves the group, not the individual, to ensure survival of the species and that groups containing selfish individuals die out because they exploit food resources
2) Largely discredited because groups do not go extinct fast enough for group selection to be an important force in evolution
3) Individuals will die fast than groups, so individual selection is likely the predominant evolutionary force of behavior
4) Immigration and emigration also reduce likelihood of selfish behavior, because their genotype would likely not spread throughout whole population and lead to fixation
Behavior p. 11-12

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9
Q

Empirical support against group selection

A

1) Most tits lay 8-9 eggs
2) Chicks in larger broods are fed less often and weigh less
3) But tit clutch size is slightly less than what would be expected to optimize number of surviving young per brood, why?
4) In an experiment where a tit was given “free chicks”, “free eggs”, and “full costs”
5) No difference in chick survival between treatments, but difference in female survival
6) There is a trade-off between increased reproductive effort and adult survival
7) Provides support for individual regulation of clutch size, rather than regulation of clutch size for the good of the group (reduced resource exploitation)
Behavior p. 14-15

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10
Q

Optimal trade-off between survival and reproductive efforts

A

1) Pianka and Parker 1975; Bell 1980
2) When plotting current reproductive effort with expectation of future reproductive success, if the curve is convex iteroparity and repeated breeding is favored (because the higher the effort, the lower the future success)
3) If the curve is concave, semelparity or big bang reproduction is favored because future reproductive success is consistently low
Behavior p. 16

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11
Q

Phenotypic plasticity

A

Ability of a single genotype to alter its phenotype in response to environmental conditions
Behavior p. 18

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12
Q

Reaction norm (phenotypic plasticity)

A

When the phenotypic variation is continuous, the relationship between phenotype and the environment for each genotype. There may be variation in both the elevation of the line (trait value) and its slope (the way trait value changes in response to environment.
Behavior p. 19

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13
Q

How to test behavior

A

1) Comparison between individuals within a species
2) Experiments
3) Comparison among species
Behavior p. 24-5

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14
Q

Comparative method of testing behavior

A

1) Because different species have evolved in relation to different ecological conditions and so comparison among species may help us to understand how different pressures shape behavior
2) Correlating species differences in behavior with differences in ecology
3) How does this differ from natural selection field studies?
4) Limitations: Need to consider alternative hypotheses (e.g. how do we know that the selective pressure we selected is the one that actually results in observed behavior), need to quantify ecological variables, need to infer cause and effect, observed behavior could be non-adaptive when we are inferring adaptive behavior, independence in statistical analysis (are you comparing one species to a whole genus?)
Behavior p. 25, 31

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15
Q

Examples of comparative method

A

1) Social organization of weaverbirds.
a) Species in forests tend to be insectivorous. Food is dispersed so they are solitary feeders that defend large territories. Because of dispersed food source, both parents must take care of young so they are monogamous. Since both males and females visit the nest they must have similar, dull plumage.
b) Species living in the savannah tended to eat seeds, which are patchy in distribution and locally superabundant. Therefore feeding in flocks is beneficial as a group can cover a greater search area and the patches can support more than one individual. Because food is abundant, females can feed their young alone, so they are polygamous and sexual dimorphism in plumage has evolved.

2) Social organization of African ungulates.
a) Small ungulates have a higher metabolic requirement per weight and need high quality food (berries and shoots) which tend to occur in the forest and are widely dispersed, so they must be solitary foragers
b) Large ungulates can eat poor quality food in bulk and are less selective. It is not economical to defend large areas for food supplies so they wander in herds to find large patches of food. The largest male can monopolize many females in the herd.
Behavior p. 29-30

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16
Q

How has sexual dimorphism evolved?

A

1) Two hypotheses: (a) Sexual dimorphism allows males and females to exploit different niches OR (b) male-male competition for mates favors larger individuals.
2) If a were true, then dimorphism would be more common in monogamous mating systems where males and females forage together
3) But the opposite pattern is seen, so b is the more likely reason
Behavior p. 35

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17
Q

Testis size and breeding system

A

Larger testes are typically indicative of sperm competition, as animals with polygamous mating systems often have larger testis
Behavior p. 37

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18
Q

Phylogenetic effects in comparative studies

A

1) Closely related species tend to have similar traits since they descended from common ancestors rather than independent evolution.
2) Adding a similar species to an analyses increases the likelihood that the trait being tested, you increase the probability of that trait being correlated across species.
3) Therefore, it is necessary to take phylogenies into account.
4) Independent contrasts may be a solution to this problem
Behavior p. 38

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19
Q

Independent contrasts

A

1) Solves the problem when species are not independent
2) We can assume that species have evolved independently since their divergence.
3) For example, in a phylogeny where A gave rise to B and C, B gave rise to D and E, and C gave rise to F and G, the independent contrasts would be A and B, D and E, and F and G.

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20
Q

Optimality approach for behavior

A

Seeks to predict which particular trade-off between costs and benefits will have the maximum net benefit to the individual
Behavior p. 47-8

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21
Q

Marginal value theorem

A

1) Animals experience diminishing returns within a patch
2) Used to predict how much time an animal foraging for itself will spend in each site before moving on
3) E.g. The optimum load for foraging starlings depends on the travel time (fixed) and search time, for longer trips the optimal load is higher than shorter trips. Fig 3.2
4) E.g. Travel time predicts the length of time fly spends copulating with female (since if two males mate with a female, the second male has a higher percentage of offspring so males want to guard females) Box 3.1
5) E.g. Bees collect less food for longer distances because the load slows them down.
Behavior p. 54

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22
Q

Optimal prey choice model

A

1) A predator encounters two prey types: prey 1 and prey 2. If prey 1 is more profitable E1/h1 > E2/h2, or rather the ratio of energy density to handling time of prey 1 is greater than prey 2.
a) if prey 1 is encountered it will eat,
b) but if prey 2 is encountered it should eat only if the abundance of prey 1 is so low such that E1/(h1+S1) < E2/h2, or the added search time of prey 1 makes the pay off for prey 2 better.
2) Therefore this model makes three predictions:
a) The predator should either just eat prey 1 (specialize) or eat both prey (generalize)
b) The decision to specialize depends only on the search time of prey 1, the more profitable prey
c) The switch from specialization to generalization is immediate once S1 increases such that E1/(h1+S1) < E2/h2 is true.
Behavior p. 61

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23
Q

What is the ‘currency’ of optimal prey choice models?

A

Handling time, energy density, and search time.

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24
Q

What is risk-sensitive foraging?

A

1) Risk of starvation is an additional currency that can be included in optimal prey choice models.
2) Animals are sensitive to both the return rate on a foraging opportunity but the variability (in prey availability)
3) E.g. Juncos were given a variable prey option, in which pay off varied from 0 to 6 seeds, and a fixed rate of .5 seeds. When their energetic needs were higher (at low temperatures) they risked the variable option because the fixed rate did not provide enough energy to avoid starvation. At higher temperatures with lower metabolic costs, birds selected the fixed food resource.
4) E.g. A small bird needs to put on energy reserves by dusk in order to survive the night. The prey options are one unit of food with probability 1 or two units of food with probability .5, so average pay-offs are the same but there is a greater variance. It’s decision will therefore depend on its current state (>=8 they survive). If the state is 6, it will take the gamble, but if the state is 7 it will play safe since that will give it just what it needs to survive without risking starvation. (Box 3.3)
5) E.g. When nests are depleted of resources, bees increase risky behavior. When nests are augmented with additional resources, bees play it safe.
Behavior p. 63-4

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25
What is the currency of foraging?
Food return and food requirement
26
Balancing predation and starvation in tits
``` When predators (hawks) are introduced, great tits reduced their mass. Additionally, more dominant birds (that have greater access to food and a less variable environment of foraging) dropped substantially more weight. Behavior p. 66 ```
27
What is the utility of optimality models?
1) Make testable predictions 2) Assumptions regarding currency and constraint are explicit 3) Generalizes simple decisions facing animals Behavior p. 79
28
Social cognition
1) The ability of an animal to behave as though it could interpret the knowledge of another individual. 2) E.g. when scrub jays are observed by other birds while caching, it would later on move its cache to avoid stealing. This happened more frequently when the observer was a more dominant bird than the cacher. Behavior p. 71
29
Mental time travel
1) The ability to project into the future, independently of current physiologic requirements 2) E.g. Scrub jays, when given the option to store food in a series of three rooms where they were held in sequence, typically hid the food in the room where they would be kept overnight so they could eat if hungry at that time Behavior p. 72
30
Evidence against animal intelligence
1) Complex behaviors can be generated by simple behavior mechanisms 2) Intelligent behavior may be a specific adaptation to a particular ecological problem, such as the memory of food storing birds 3) Even humans use subconscious rules of thumb rather than conscious calculations Behavior p. 73
31
Social learning
1) Using the behavior of others as a source of information 2) E.g. nine-spined sticklebacks (more at risk of predation) rely on public information to find the appropriate patch to forage in, but three-spined sticklebacks (less at risk of predation) rely only on their own experiences.
32
Red Queen Evolution
1) Evolving to keep up with rivals. 2) E.g. When Daphnia were exposed to parasites from the same sediment layer (contemporary parasites) and from sediment layers with past and future parasite populations, infectivity was higher with contemporary parasites than with parasites from previous growing seasons. Therefore, Daphnia evolved to beat past parasite genotypes while the parasites, in turn, rapidly evolved to adapt to the changing host genotypes. Behavior p. 84
33
Polymorphic cryptic coloration
1) Different colour forms exist within same species 2) Polymorphic prey prevents search image use by predators 3) Experiments on jays support this as detect prey easier when shown images of prey with the same coloration repeatedly when compared to switching the morph/coloration of prey in successive trials Behavior p. 87,89
34
Search images (predator)
When predators improve their ability to see cryptic prey by searching for similar "patterns" against camouflage Behavior p. 88
35
Apostatic selection
rarer prey types have an advantage | Behavior p. 89
36
How does prey polymorphism evolve?
In a population, abundance of most cryptic form increases (since predators initially go for more conspicuous forms), until an equilibrium is reached where previously cryptic form is most abundant, and two other morphs persist, Fig 4.6 Behavior p. 90
37
Does slight concealment (crude crypsis) of prey have an advantage?
1) Yes, in an experiment where Great tits were presented with inedible twigs, large cryptic prey (meal worm in a straw), and small conspicuous prey, they often chose small conspicuous prey because the time it took to distinguish the twig from the large cryptic prey was not an optimal decision 2) Handling time increases with crude crypsis Behavior p. 91
38
Disruptive coloration
When coloration "breaks up" the body outline to further disguise prey and confuse predators Behavior p. 92
39
Countershading
Darker coloration on dorsal surface, giving the prey a "flat" appearance as shadows won't show Behavior p. 93
40
Masquerade
Resemblance of inedible objects, camouflage without crypsis. | Behavior p. 94
41
Aposematism
1) Honest signaling of toxicity through bright coloration 2) Conspicuous colors help predators to learn to avoid unpalatable prey 3) Costs of aposematism vary depending on predation pressure and trade-offs between investing in repellent defenses versus colorful signals. Behavior p. 96-97, 103
42
Evolution of aposematism
1) Plausible that conspicuous colors evolved first via sexual selection, but that these conspicuous colors increased predation risk, so distastefulness evolved secondarily. 2) Plausible that unpalatability evolved first followed by conspicuousness, specifically in family groups. Essentially a mutation for bright coloration evolves in a distasteful species, the predator then only has to eat one individual with the bright coloration to learn that it is unpalatable, therefore the bright colored individuals survive via kin selection. 3) Grouping may have evolved after warning colors. Behavior p. 98-99
43
Mimicry
Association between bright colors and repellent defenses has led to the evolution of Batesian and Mullerian mimicry Behavior p. 100
44
Mullerian mimicry
1) Repellent species look alike 2) Promotes uniformity in color pattern Behavior p. 100
45
Batesian mimicry
1) Cheating by palatable species 2) Promotes polymorphism because mimetic patterns will be at an advantage when rare relative to the model (when predators are more likely to eat noxious models) and at a disadvantage when common (predators more likely to sample palatable mimics) Behavior p. 102
46
Evolution of cuckoo brood parasitism
Cuckoos parasitize nests by mimicking their eggs. The hatched cuckoo then throws the other eggs in the nest out. Cuckoos have evolved in response to hosts through the use of mimetic eggs, timing of laying, and unusually fast laying. Hosts have evolved to discriminate between their own eggs and that of a parasite and have evolved more distinctive egg patterns. However, discrimination at the chick stage is too costly. Behavior p. 106-8
47
Evolutionary Stable Strategy (ESS)
1) A strategy that, if all members of a population adopt it, cannot be improved by a alternative strategy 2) E.g., If one person at an outdoor concert stands, then everyone must stand. 3) Not necessarily an optimal strategy, but strategy at which system settles where cheaters cannot dismantle it 4) Population behavior depends on community composition (frequencies of each strategy reach a point where average payoff is equal, making the system stable) Behavior p. 116
48
Hawk-Dove Game
1) Hawks always fight to injure opponents 2) Doves always share the resource 3) Dove versus dove, resource is split evenly and each animal accrues equal fitness benefit 4) Dove versus hawk, dove accrues no fitness 5) Hawk versus hawk, both incur injuries so fitness benefit is equally decreased 6) Hawk versus dove, hawk wins and accrues all possible fitness 7) Each strategy does best when rare Behavior p. 117
49
Ideal free distribution
1) Ideal = having perfect knowledge, Free = free to move 2) Assumes that animals know ideal habitat and are free to go anywhere and will not be hindered from going to new location 3) E.g., distribution of ducks in a pond 4) Can test either numerical prediction, equal intake prediction, or prey risk predation 5) Assumes stochasticity (equal intake prediction better suited for stochastic environment, e.g. male dung flies competing for mates) Behavior p. 119-122
50
Despotic distribution
1) Resource defense 2) First competitors settle in rich habitat, second competitors settle in poor habitat, and final competitors must find new habitat 3) E.g., Great tits use oak woodland for breeding in spring, but last competitors must use hedgerows where there is less food and lower breeding success Behavior p. 123
51
Ideal free distribution with unequal competitors
1) Subordinates distribute themselves relative to the behavior of the despots 2) E.g., habitat selection in aphids, want to occupy large leaves to create galls because number of progeny depends on resources utilized, additional settlers can choose to pick share resources on large leaf or smaller leaf solitarily Behavior p. 123-4
52
Economic defensibility
1) Resource or territory is defendable if cost of maintenance is smaller than benefit 2) If resources are at low density, gains of excluding others may not outweigh the costs 3) May be an upper threshold of resource availability beyond which defense is not economical, e.g. many intruders 4) E.g., Gill and Wolf's sunbirds (past certain threshold, high nectar levels are not protected as territorial defense does not save foraging time. Behavior p. 126
53
Alternative strategy
1) Genetically based decision rule (e.g. always sneak or always fight) 2) Good to be rare, e.g. spice finches have a higher frequency of scroungers, as it continues to increase the pay-off decreases and producers will be favored Behavior p. 132, 139
54
Conditional strategy
Individuals vary their competitive behavior depending on something like body size (e.g. fighting in horned beetles, horns only grow past certain body size) Behavior p. 132
55
Tactic
Behavior pattern displayed as part of strategy. | Behavior p. 132
56
Conditional strategies with alternative tactic
1) Natterjack toads: callers and satellites 2) large toads are callers, small toads are satellites 3) but behavior varied based on degree of competition for larger males Behavior p. 133
57
Sinervo's lizard mating morphs
1) rock paper scissors 2) orange lizards are aggressive and defend large territories 3) yellow males look like females 3) blue males are less aggressive and defend small territories 4) frequency of morphs depends who the winner is Behavior p. 141
58
Pros of group living
1) Protection from climatic extremes 2) Advantages in locomotion 3) Reducing predation a) Dilute risk of attack b) Predator confusion c) Communal defense d) Improved vigilance for predators 4) Improving foraging success a) Better food finding (information centers) b) Better food capture (group hunting) Behavior p. 148
59
Cons of group living
1) More conspicuous to predators 2) higher attack rate per group (not per individual) Behavior p. 148
60
Dilution theory
1) Groups lower the probability of attack for an individual 2) E.g., winter aggregations of monarch butterflies. Although not a very palatable butterfly, birds will still attack them when they roost, predation rate per individual still lower in groups Behavior p. 148-9
61
Predator swamping
1) Synchrony in time swamps the predator's ability to capture prey 2) E.g., individual mayflies are safest from predation during days when more adults emerge (could be argued this synchronized mating increases breeding success, but it is also seen in parthenogenetic flies). Behavior p. 150
62
Selfish herds
1) Individuals that approach each other reduce their domain of danger 2) E.g., swarms, flocks, and shoals as individuals try to gain safest position in the group 3) E.g. fur seal experiment with sharks Behavior p. 151
63
Predator confusion
1) Grouping confuses predator attacks 2) E.g., increasing prey shoal size decreases success of predator attack Behavior p. 151
64
Communal defense
1) Groups may attack or mob a predator 2) E.g. gulls attack crows Behavior p. 153
65
Improved vigilance for predators
1) Individuals in larger groups detect predators sooner 2) Individuals in groups can also scan less if group number is high 3) E.g. as group size in ostriches increased, the amount of time an individual had to be vigilant decreased Behavior p. 155
66
Cheaters in groups
1) Vigilance is a game that depends on group behavior 2) Vigilance strategy must be an ESS 3) Temptation to cheat is reduced if individual who spots predator first gains extra advantage a) Predators may be less likely to target vigilant individuals b) Vigilant individuals flee more quickly Behavior p. 156-7
67
Sentinels
1) Sentinels warn others, but do not behave altruistically 2) Sentinels only go watch when they are satiated 3) Sentinels detect a predator sooner and may be able to flee quicker Behavior p. 157-8
68
Group foraging (information centers)
1) individuals that have patchy, dense aggregations of food often live in groups 2) Colonies can act as information centers 3) If there is little cost to foraging in a group and if pooling information increases likelihood of finding food, "search independently and recruit others from the colony or roost" can be an ESS Behavior p. 159
69
Group foraging (prey capture)
1) Group hunting may improve prey capture 2) There is often an optimal group size for foraging, but this optimal size is not stable unless there is a way to kick out extra group members Behavior p. 161-2
70
Evolution of group living
Guppies in predator-rich pools began to form shoals | Behavior p. 167
71
Skew theory
1) In groups there are individual differences in fitness (based on position, etc.) 2) Subordinate individuals will put up with lower payoffs so long as they could not do better by moving elsewhere 3) Skew models consider the effects of group size on individual reproductive success 4) There may be a tug of war between resources between dominants or subordinates, or dominants may evict subordinates that take up too many resources (e.g. subordinate coral reef fish may constrain growth to avoid eviction) Behavior p. 167-8
72
Isogamy
Gametes are the same size | Behavior p. 180
73
Anisogamy
Gametes are different sizes | Behavior p. 180
74
Evolution of anisogamy
1) Assume survival of a zygote depends on size 2) Larger zygote == more food to sustain its development == favored by selection (if higher survival compensated for the fact that fewer gametes could now be produced) 3) Once larger gametes evolve, there is selection on smaller gametes to seek out larger gametes to fuse with (to parasitize food reserves) 4) Fusion between small and large gametes will predominate (although fusion of two large gametes will be best option, they cannot find each other) 5) Selection acts more strongly on small gametes, and they will eventually 'outwit' defenses of large gamete 6) Producers of intermediate gametes lose out because they do have have great numbers or large benefits Behavior p. 180-1
75
How is anisogamy maintained?
1) Sperm competition 2) If a mutant bull produced sperm that was larger than other sperms, it would not increase the nutrients of the zygote by a large factor, yet the number of sperms able to be produced would be greatly reduced Behavior p. 181
76
Theory of Robert Trivers
1) The sex with the least parental investment has a greater potential rate of reproduction 2) While a female can best increase her reproductive success by increasing the rate of converting resources into eggs and offspring, a male can best increase his success by finding and fertilizing many different females Behavior p. 182
77
Bateman's principle
1) Males have greater variability in reproductive success than females (increases with number of mates) because they are limited by females 2) Females are limited by resources (varies but does not increase with number of mates) 2) Demonstrated with drosophila Behavior p. 182-3
78
Queller's theory
1) Polyandry and sexual selection lead to skewed mating success among males 2) Males are less likely to give parental care because they may not have parentage of all offspring 3) Although potential reproductive rate of males is higher, their average reproductive rate is equal to that of females if the sex ratio is 1:1 4) Competition among males from female investment increases, and successful males are less inclined to care after mating 5) As females provide more care, sexual selection on males intensifies (positive feedback) Behavior p. 184
79
Evidence for sexual selection
1) Traits that improve a male's success in combat (e.g. large size, sexual dimorphism) 2) Female choice Behavior p. 187-8
80
Why are females choosy?
1) Good resources (e.g. male bullfrogs defend territories that enable better egg success) 2) Good genes (e.g. bowerbird nests may demonstrate their ability to protect and replenish resources, which is a trait that can possibly be passed to male offspring) Behavior p. 193-4
81
What are the two hypotheses of genetic benefits from female choice?
1) Fisher's hypothesis | 2) Handicap hypothesis
82
Fisher's hypothesis
1) Females prefer a male trait because it indicates something about male quality 2) E.g. maybe widowbirds with slightly longer tails could fly better and collect more food. Or longer tails are selectively neutral but make males more conspicuous to females. If there is some genetic basis for differences between males in tail length the advantage will be passed on to the female's sons while a gene causing females to prefer longer tails will also be passed down. 3) Leads to Fisher's runaway
83
Zahavi's handicap hypothesis
1) Females choose a trait because it demonstrates that the male can overcome an energetically costly hindrance 2) E.g. female widowbirds choose long tails because they are handicaps and therefore act as a reliable signal of a male's genetic quality 3) Evidence: males only express the handicap (develop the display) when they are in good condition
84
How is genetic variation for quality maintained over the generations?
1) Populations suffer from a continuous input of deleterious mutations, so it pays for females to always be choosy 2) If only males in the best condition can afford to grow elaborate ornaments, or have vigorous displays, then female choice is unlikely to deplete the genetic variation underlying multiple sexual ornaments 3) Females may choose different male traits in different years 4) Host-parasitic arms races maintain genetic variation Behavior p. 196
85
How does disease resistance play a role in sexual selection? (Hamilton-Zuk hypothesis)
1) Disease is a powerful selection pressure on organisms 2) Sexual displays may be reliable indicators of genetic resistance to disease. 3) According to this view, by choosing for elaborate displays females are selecting males that are genetically equipped to resist current infection 4) The 'good genes' are changing all the time so it pays for females to be choosy Behavior p. 196
86
What is necessary to support Fisher's hypothesis?
1) Genetic variation in female preference 2) Genetic variation in male trait 3) Preference and trait genes covary Behavior p. 196
87
Support for Fisher's hypothesis
1) Male stalk-eyed flies with large eye spans were accompanied by more females 2) Females preferred males with largest eye spans in lab experiments 3) In artificial selection experiments, selecting only for male eye span they found that the females preference also changed (females bred with long eye span males continued to prefer this trait, while females bred with short eye span males continued to prefer this trait) Behavior p. 198
88
Support for 'good genes' hypothesis of sexual selection
1) Sons and daughters of male peafowls with very ornamented tail grew better and survived better Behavior p. 199
89
What needs to be tested for Hamilton-Zuk hypothesis
1) Parasites reduce host fitness 2) Parasite resistance is genetic 3) Parasite resistance is signalled by elaboration of sexual ornaments 4) Females prefer males with the most elaborate signals Behavior p. 200
90
Support for Hamilton-Zuk hypothesis
1) Female sticklebacks prefer to mate with redder males 2) Red coloration signals physical condition 3) When bright males were infected with parasites, red intensity declined Behavior p. 200
91
Seasonal variation in sexual competition
1) Katydid's demonstrate seasonal variation in sexual competition 2) When food is scarce, male's large protein-rich spermatophore is costly to produce and also very valuable to females, therefore, females compete for males and males are choosy 3) When pollen-rich grass tress come into flower, males can produce spermatophores more rapidly and access to receptive females now limits male success, therefore, males compete for females 4) Or, when sex ratio of gobies is female-biased females compete for access to males, but when ratio is 1:1 males compete for females Behavior p. 203-4
92
Why would a female mate with several males?
1) Cost of resistance exceeds cost of acquiescence (e.g., female dung flies may drown in the cowpat as the male struggles for possession) 2) Indirect benefits from multiple mating (e.g., increased mating yields increased parentage from multiple males, decreasing the likelihood that her offspring will be killed and increasing the likelihood that her offspring will be cared for, e.g. ensuring fertility, e.g. food gifts or nutrients from male courtship) 3) Direct (genetic) benefits (e.g. female increases genetic quality of offspring by mating with more than one male, e.g. extra-pair matings from female birds ensures social mate will help care for offspring, but extra mate provides genetic benefit to offspring) Behavior p. 205-7
93
Hypotheses for what limits extra-pair mating?
1) Social mate reduces care when cuckoldry is suspected 2) Different sires are best for sons and daughters (possibly because of sexually antagonistic genes, e.g. increased hip width in females) Behavior p. 208
94
Sexual conflict
1) Optimal outcome is different for male and female 2) Leads to each sex evolving adaptations that bias the outcome towards its own interests, leading to sexually antagonistic coevolution between traits in males and females Behavior p. 209
95
Sexual conflict over mating
Antagonistic coevolution: Enforced copulation == resistance Intromittant organs which enhance mating success == elaborate reproductive tracts with pose obstacles for sperm Mate guarding, frequent copulation, strategic allocation of sperm == seek extra-pair copulation Remove or displace rival sperm == sperm ejection Copulatory plugs and anti-aphrodisiacs == sperm choice Accessory gland proteins to manipulate females == chemical defense Behavior p. 210
96
Coolidge effect
Male's sperm investment declined with repeated exposure to the same female but was renewed by the arrival of a novel female Behavior p. 215
97
Sexual conflict and mating systems
1) Monogamous females typically have less defenses 2) Males evolve to be less harmful to females and females evolve to be less resistant in monogamous mating systems Behavior p. 218
98
Parental care and family conflicts
1) Male and female parents 2) Between siblings 3) Parents and offspring Behavior p. 223
99
Parental care for taxon
Inverts == parental care is uncommon Fish == 9:3:1 ratio of male (external fertilization), biparental, and female care (internal fertilization) Amphibians == low frequency of any parental care Reptiles == either female alone or both parents Birds == 90% biparental care, female care alone in most other species Mammals == Females care in all species, 95% female only Behavior p. 224
100
Why is male care more common with external fertilization and female care more common with internal fertilization?
1) Paternity certainty 2) Order of gamete release (perhaps males must weight to fertilize eggs since eggs are lighter than sperm, but this is rejected on empirical grounds as most common pattern of gamete release is simultaneous 3) Association (male fish more closely associated with embryos as they are laid in male territories) Behavior p. 226-7
101
Parental investment
Any investment by the parent in an individual offspring that increases the offspring's chance of surviving at the cost of the parent's ability to invest in other offspring Behavior p. 227
102
Trade-offs between offspring quantity and quality within and amongst broods
1) If a parent spreads its limited resources thinly among too many offspring, then few will survive (within) 2) If it uses resources too generously on a small brood, then other parent swill produce more surviving young (within) 3) Increased investment in any one brood decreases future reproductive success (amongst) Behavior p. 227-8
103
Flexible parental response to current brood demands
1) Increased begging behavior of offspring increases resource provisioning by parent 2) Parents strategically varied sensitivity to current brood's demands in relation to future prospects of breeding that season 3) But there is a cost to begging to the offspring so they cannot "over ask" 4) E.g. When small St. Peter's male fish cannot hold many eggs in their mouth they are more likely to desert (i.e., males are more likely to desert when the benefits they gain from care are reduced) Behavior p. 230-1
104
Filial cannibalism
1) When parents eat offspring 2) Might sometimes be adaptive for a parent to use its offspring as an extra food source 3) Eating part of brood increases parental care for the remaining offspring 4) Eating the whole brood cuts parental losses and improves future reproductive success Behavior p. 232
105
ESS model of parental investment: female and male deserts
If W=eggs laid by deserting female and w=eggs laid by caring females P0=probability of egg survival if it receives care from 0 parents P1=probability of egg survival if it receives care from 1 parents P2=probability of egg survival if it receives care from 2 parents 1) Females and males can desert when WP0>wP1 (probability of care from 0 parents is greater than if only female cares) and P0(1+p)>P1 Behavior p. 233
106
ESS model of parental investment: female deserts and male cares
If W=eggs laid by deserting female and w=eggs laid by caring females P0=probability of egg survival if it receives care from 0 parents P1=probability of egg survival if it receives care from 1 parents P2=probability of egg survival if it receives care from 2 parents 1) Female deserts and males cares when WP1>wP2 (probability of survival from care from 1 male is greater than if male and female cared) and P1>P0(1+p) Behavior p. 233
107
ESS model of parental investment: female cares and male deserts
If W=eggs laid by deserting female and w=eggs laid by caring females P0=probability of egg survival if it receives care from 0 parents P1=probability of egg survival if it receives care from 1 parents P2=probability of egg survival if it receives care from 2 parents 1) Female cares and males deserts when wP1>WP0 (probability of survival from care from 1 female is greater than if male and female deserted) and P1>P0(1+p) Behavior p. 234
108
ESS model of parental investment: female and male cares
If W=eggs laid by deserting female and w=eggs laid by caring females P0=probability of egg survival if it receives care from 0 parents P1=probability of egg survival if it receives care from 1 parents P2=probability of egg survival if it receives care from 2 parents 1) Female cares and males cares when wP2>WP1 (probability of survival from care from both parents is greater than if only the male cared) and P1>P0(1+p) Behavior p. 234
109
How is parental care stabilized?
1) At the ESS, each parent will invest a fixed amount of effort that maximizes its own fitness, given the effort invested by its mate 2) If brood productivity is an increasing function of parental investment with a saturation point, and costs parental investment increase linearly, then the 'best response' of each parent will involve incomplete compensation 3) If one parent reduces effort, the other will increase effort, but not enough to fully compensate, maintaining a stable investment in the ESS and reducing cheating. Behavior p. 235
110
Intrabrood conflict
1) Each offspring should demand more than its fair share from the parent's point of view 2) This because siblings are, at best, only share .5 genes, or less in polygamous and multiple-mating species Behavior p. 238
111
Interbrood conflict
1) Current broods should demand more at the expense of future broods Behavior p. 239
112
Evidence of sibling rivalry
1) Facultative siblicide (siblicide depends on condition of elder chick or sibling, insures survival of first offspring if condition is poor, e.g. Galapagos fur seals) 2) Obligate siblicide (production of two offspring is used as an insurance policy that at least one survives, first sibling ALWAYS kills second sibling) 3) Sibling relatedness influences rivalry (as relatedness decreases, begging behavior from individual offspring increases because there is a reduced cost of depriving them resources) Behavior p. 240-1
113
Evidence of parent-offspring conflict
1) Behavioral squabbles between parent and offspring (e.g. Galapagos fur seal parent trying to tear second offspring away from first) 2) Sex ratio conflict (queen hymenoptera prefer a 1:1 sex ratio because she is equally related to both, but workers prefer sister siblings as they are more related because they are diploid, so workers may destroy male eggs) 3) Conflicts during pregnancy (when genes in the offspring attempt to parasitize more resources from the mother, and the mother attempts to resist these demands) Behavior p. 243-6
114
Genomic imprinting and parent-offspring conflict
1) Genomic imprinting may evolve from parent-offspring conflict 2) Paternal genes in offspring are predicted to demand more maternal resources than are maternal genes in the same offspring 3) Genomic imprinting is favored in these conditions, enabling genes to play a condition strategy depending on whether they were derived from the mother or father Behavior p. 246
115
Resolution of parent-offspring conflict
1) Costly begging may resolve parent-offspring conflict 2) There is coadaptation of offspring demand and parental provisioning (offspring from generous mothers beg more) Behavior p. 246-7
116
Monogamy
One male restricts his matings to one female, and she to him, either for one breeding season or longer. Both partners may forgo other mating opportunities by choice, or one partner may enforce monogamy by keeping other potential mates at bay. Often both parents care for the eggs and young. Behavior p. 255
117
Polygyny
One male mates with several females in a breeding season by defending them directly (a harem or female defense polygyny), or by defending resources that the females require (resource-defense polygyny), or by attracting females to a display site, sometimes where many males aggregate together (leks), or by the male roaming in search of widely dispersed females (Scramble competition polygyny). often the female provides most or all of the parental care. Behavior p. 255
118
Polyandry
One female mates with several males in a breeding season by defending them simultaneously or in succession. Often the male provides most or all of the parental care. Behavior p. 255
119
Promiscuity
Both male and female have multiple partners during a breeding season Behavior p. 255
120
Polygamy
A general term for when an individual of either sex has more than one mate Behavior p. 255
121
Resource dispersion and mating system
1) Typically, when resources are scarce females or groups of females tend to spread out, this limits male access to females, as a result the mating system tends to be polygamous as males can then defend resources or territories that are necessary for females as a way to attract them and mate 2) E.g., in both voles and wrasse, females follow resources (when resources are spaced out) while males follow females Behavior p. 254
122
Home ranges and mating system
1) If solitary female ranges are extremely large, then the male may only be able to defend one female (monogamy) 2) Obligate monogamy occurs where female ranges are small enough for a male to defense but too large to have more than one solitary female 3) When females are social and occur in a mall range, then a single male may be able to defend them as a permanent harem within his territory (polygamy) (sometimes several males defend a territory together and share females) 4) When females are social and range widely males may wait for females, follow females, or use harem defense or seasonal harems (when oestrus is seasonal) or permanent harems (when oestrus is asynchronous) Behavior p. 257-9
123
Leks
1) Aggregations of males on small mating territories 2) Typically occurs when neither resources nor females can be economically defended Behavior p. 260
124
Hypotheses for why males aggregate into leks
1) Leks may occur on hotspots where females are abundant 2) Males aggregate to increase female attraction via synergistic displays 3) Males aggregate to reduce predation risk via dilution effect 4) Males aggregate around attractive "hotshot" males, e.g. satellite and calling male toads 5) Females prefer male aggregations because they facilitate mate choice Behavior p. 261-3
125
Obligate monogamy: fidelity and divorce
1) Occurs if each male and each female will, on average, leave most descendants if they share in raising a brood (possibly because forming this sort of team increases offspring survival) 2) Initiators of divorce typically move to better breeding areas and gained while victims lost 3) E.g., oystercatchers Behavior p. 264-5
126
Fitness consequences of divorce
1) Victim of desertion is abandoned by mate and remains in the same territory 2) Deserter abandons mate and moves to an improved territory 3) Victim of usurpation is forced to abandon mate and leaves territory 4) Bystander loses old mate, but gains a new mate, remains in territory Behavior p. 265
127
Why are birds monogamous?
1) There are limited opportunities for polygyny 2) Strong competition by males may make it difficult for a male to gain a second female 3) Females are likely to suffer in polygyny through the loss of male help 4) Females are aggressive to other females, reducing opportunities for males 5) Lack's hypothesis was wrong (monogamy is not the most beneficial strategy for both of the sexes) Behavior p. 265
128
Polygyny Threshold Model
1) In some species, females may not experience polygyny costs 2) But some females male suffer from having to share resources a male controls 3) Females may choose polygyny because the costs are outweighed by the benefits, e.g. Great Reed Warblers Behavior p. 269
129
Why may females settle polygynously?
1) The sexy son hypothesis (So son will be able to reproduce more) 2) Females may be deceived by males to make it appear as though they are not with other females 3) Unmated males may be hard to find Behavior p. 273-4
130
Polygynadry
1) Can occur when each sex favor polygamy 2) E.g., dunnocks 3) Is a stalemate outcome to conflict Behavior p. 275
131
Polyandry Threshold
1) Males do better by agreeing to share a female rather than attempting to go it alone in monogamy 2) Typically when resources are scarce and when there is intense competition for females 3) E.g., Male lions and Galapagos hawks Behavior p. 277
132
What influences mating systems?
1) Life history constraints (differences between orders and families) 2) Ecological factors (differences between related species) 3) Social conflicts (differences within species or populations) Behavior p. 279
133
Sex allocation
Allocation of resources to male versus female reproduction in sexual species Behavior p. 282
134
Fisher's theory of equal investment
1) A female-biased sex ratio is not evolutionarily stable because a gene which causes parents to bias the sex ratio of their offspring towards males would rapidly spread (because males can produce more than females as females are limited by one egg, typically, and parental care) 2) The reverse is also true, as if females are rare, males have a lower probability of mating 3) Therefore, the rarer sex will have an advantage, leading to a 1:1 sex ratio being favored by natural selection 4) At a 1:1 sex ratio, male and female offspring have the same number of their own offspring, but males are more expensive to make 5) When sons and daughters cost different amounts to make, the stable strategy is for the parent to invest equally in the two sexes and not to produce equal numbers Behavior p. 285
135
Altruism
1) Benefit to others, cost to actor | Behavior p. 306
136
Coefficient of relatedness
1) Measures the genetic similarity of two individuals relative to the population at large Behavior p. 308
137
Hamilton's rule
rB-C>0, the benefit of helping kin must be larger than the cost to the actor Behavior p. 313
138
Suicide and sterility in social insects
1) An example of extreme altruism 2) Workers are unable to reproduce themselves 3) Helps others in nest to produce offspring (typically their mother, the queen) 4) Queen passes altruistic genes to future generations Behavior p. 314
139
Altruistic alarm calls
1) Belding's ground squirrels and prairie dogs 2) Alarms are given when relatives are nearby Behavior p. 315
140
Quantitative test of Hamilton's rule with wild turkeys
1) Brothers search for mates together 2) One is dominant and one is subordinate 3) Subordinate male does not reproduce, but helps dominant mate 4) Math fits into Hamilton's rule 5) Called cooperative courtship Behavior p. 317
141
Greenbeards
1) Cause altruistic behaviors to be directed at other individuals who carry that gene 2) Fire ants have a greenbeard gene, causing workers to eliminate queens that do not have this gene 3) Can be outcompeted by falsebeards Behavior p. 319
142
Methods of kin discrimination
1) Typically through odors | Behavior p. 319
143
Altruism in slime mold stalk cells
1) Slime molds will combine to form a motile slug 2) The slug will become a fruiting body with a stalk and a head of spores 3) The stalk does not reproduce 4) Only occurs when slime molds are related Behavior p. 320
144
Kin discrimination in ground squirrels
1) Female ground squirrels recognize kin partly by learning and partly by phenotype matching 2) Odors from oral and dorsal glands play a mechanistic role in kin discrimination Behavior p. 322
145
Fixed and conditional strategies in kin selection
1) A fixed strategy occurs when kin discrimination is not possible, treat everyone near you as kin (e.g. brood parasites are not discriminated against at chick stage because they are in the nest) 2) A conditional strategy occurs when kin discrimination is possible, only help when you know your kin are present Behavior p. 322-3
146
Selfish restraint
1) Acting less selfishly in presence of kin 2) E.g., Salamander cannibalism occurs less in presence of kin Behavior p. 325
147
Spite
1) Cost to others and actor 2) For spite to evolve, negative relatedness is required (less related to actor than the population average 3) Conditions for spite include a cost to the actor (no long-term direct benefit) and harming behaviors are directed towards unrelated individuals Behavior p. 327-9
148
Inclusive fitness
1) Direct benefits plus indirect benefits of actor 2) Direct benefit == own fitness 3) Indirect benefit == fitness of relative weighted by relatedness Behavior p. 312
149
Cooperation
1) Provides a benefit to another individual 2) Has been selected for because of its beneficial effect on recipient 3) Includes altruistic and mutually beneficial behaviors Behavior p. 335
150
Cooperative breeders
1) Subordinates help rear the offspring of dominant individuals 2) Common in eusocial insects Behavior p. 335-6
151
Prisoner's dilemma model
1) Cooperation is not an evolutionary stable strategy 2) In a population of cooperators, a mutant that defected would spread 3) In a population of defect, a mutant cooperator does not gain an advantage 4) A mixed population of strategies will evolve to "all defect" https: //www.quantamagazine.org/game-theory-explains-how-cooperation-evolved-20150212 https: //www.ncbi.nlm.nih.gov/pmc/articles/PMC4802975/ Behavior p. 337
152
Four hypotheses of cooperations
1) Kin selection 2) By-product benefits (arises as a by-product of an otherwise selfish act, example on p 341-3) 3) Reciprocity (individual will help actor in the future, example starts p 345) 4) Enforcement (rewarding cooperation and punishing free-riding, example starts p 350) Behavior p. 338
153
Example of kin discrimination in long-tailed tits
1) Helping provides clear benefits to chick survival 2) Long-tailed tits preferentially go and help at the nests of close relatives 3) Individuals gain fitness through breeding or helping, but rarely both 4) Kin discrimination occurs via the churr call Behavior p. 339
154
Hidden benefits in cooperation (example)
1) In the superb fairy-wren, helpers don't lead to an increase in chick size because mothers with helpers lay smaller eggs 2) But helpers increase the chance that breeders survive to breed again in future years Behavior p. 341
155
By-product benefits in cooperation (example)
1) Cooperative nest founding in ants occurs when unrelated queen ants join together and cooperatively form nests 2) However, during breeding they fight to the death Behavior p. 343-4
156
Reciprocity in cooperation (example)
1) Vampire bats provide blood meals for hungry bats 2) Occurs for both relatives and non-relatives 3) Occurs when there are often repeated interactions between individuals Behavior p. 347-8
157
Tit for tat
1) cooperate on first move, then do whatever your opponent did on the previous move 2) Can be beaten by tat for tit, when you start by not cooperating and only switch to cooperating in response to the cooperation of others Behavior p. 346
158
Enforcement in cooperation (example)
1) Non-helpers are punished in meerkats 2) Dominants evict subordinates that do not help to prevent them from breeding Behavior p. 351
159
Manipulation in cooperation
1) Individuals may be tricked into helping others | Behavior p. 356-8

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