Ben Hatchwell's lectures Flashcards
W. D. Hamilton’s … … theory:
“The social behaviour of a species evolves in such a way that in each distinct behaviour-evoking situation the individual will seem to value his neighbour’s fitness against his own according to the … of relationship appropriate to that situation” - 1964
inclusive fitness, coefficients
The essence of inclusive fitness theory is that individuals can gain fitness in two ways:
- by … themselves (direct fitness)
- by interacting with …. (indirect fitness)
reproducing, relatives (because of shared genetic interest)
Hamilton’s rule: A behaviour will be favoured if … < …
c, br
c =
cost to actor of social behaviour
b =
benefit to recipient of social behaviour
r =
(coefficient of) genetic relatedness between actor and recipient
- not simply shared genetic material, but sharing of genes that are identical by descent (probability of sharing the same allele)
Between parent and offspring r = …
Between siblings r = …
Between uncles and nephews r = …
Between half siblings r = …
Between cousins r = …
0.5, 0.5, 0.25, 0.25, 0.125
Look at slide 11:35 lecture 9
stuff about when c and b are positive/negative
Look at cannibalism slide in phone folder
nice
Tiger salamanders are more likely to develop into cannibalistic morphs if they are in groups containing:
- … conspecifics
- variation in … size
- mostly … individuals - most relevant part to Hamilton’s rule
many (as not even many individuals around to eat and more likely to be related), larval (as females lay many eggs in one go, relatedness is less likely if larvae vary a lot in size as it is likely they have come from different females), unrelated
Game theory: an individual’s behavioural response should depend on the…
behaviour of the individuals around them in the population
An e.g. of game theory is shown in … …: if others are producing sons, it’s better to produce … as this will maximise the number of …-…. If the … … is even, it’s better to produce an even ratio of sons and daughters. This is called an Evolutionary … … (ESS), as it cannot be invaded by a better strategy - Nash equilibrium
sex ratios, daughters, grand-offspring, sex ratio, stable strategy
Hymenoptera females can choose the sex of their offspring as they are …. If they lay a fertilised egg it develops into a …, if they lay an unfertilised egg it will develop into a ….
haplodiploid, female, male
At an even sex ratio sons and daughters give equal … returns. The even sex ration is an ESS. If there is an excess of females in a population then the number of grand-offspring gained per … is greater than the number of grand-offspring gained per …, so a female should over-produce …, driving the population towards…
fitness, son, daughter, sons, a 1:1 sex ratio
- and vice versa
John …-… was a mathematical biologist who was instrumental in introducing the idea of game theory into biology.
Maynard-Smith
The two pairwise contests we will look at are:
- The Hawk-Dove game
- The Hawk-Dove-Bourgeois Game
The Hawk-Dove game imagines that each individual in a population plays one of two strategies. Animals compete for resources in pairs. A Hawk never … and always …, and a dove will …, never … and … if an opponent fights.
share, fights, share, fights, retreats
In this model we must assign fitness payoffs:
v = …
c = …
the value of a resource that is being competed for
the cost of fighting to the loser
We can then put these into a payoff …
matrix
Watch lecture 9 32:00 - 33:55
about hawk-dove matrix
When a hawk comes across a hawk what is the payoff?
(v-c)/2
When a hawk comes across a dove what is the payoff?
v
When a dove comes across a hawk what is the payoff?
0
When a dove comes across a dove what is the payoff?
v/2
Given these payoffs what is the most evolutionary stable strategy? You’d initially assume the hawk strategy as the payoffs look more likely to be high. But it is not that simple. Hawk always wins against Dove, but pays a fighting cost. Dove never fights so doesn’t pay a cost and always shares so it gets some payoff.
If we imagine a population entirely made of doves in which rare mutant hawk strategist arises. Can the hawk invade this population?
The hawk easily invades if v > v/2 (i.e. always)
If we imagine a population made entirely of hawks in which a rare mutant dove strategist arises, can the dove invade?
Dove invades if 0 > (v - c)/2 (i.e. if c > v)
may arise if fighting is very costly
- Hawk can invade a population of Doves if v > v/2
- Dove can invade a population of Hawks if c > v
If 1 and 2 are both true, we get…
invasion from both ends: a mixed ESS, where the payoff of both strategies is equal
(see photo on phone)
If only 1 is true then we get…
a pure ESS of hawks
If only 2 is true then we get…
a pure ESS of doves
Animals don’t necessarily compete for resources as it is not always going to pay off to do so - depends on the strategy that other individuals in the population are adopting, what the costs of competing are, and what the value of the resource that they are competing for is.
Summary innit
John Maynard-Smith also considered another “game”, which he called the Hawk-Dove-Bourgeois game. In this game the Bourgeois is introduced, who…
plays Hawk when resident and Dove when intruder
The outcome of the Hawk-Dove-Borgeois game is the “… …” convention. Bourgeois always invades …, and can invade … and resists Hawks if …
resident wins, dove, hawk, v < c
This rule of … winning does seem to be the case in natural systems
residents
Speckled Wood butterflies: sit on sun patches on the floor of the wood. Periodically, males that are flying around in the canopy will come down towards a sun patch and, if the patch is already occupied by another speckled wood, they will have a brief … flight and the … will always win that brief encounter. The … will retreat to the canopy.
spiral, resident, intruder
In an experiment, residents were removed from sun patches, allowing … to now settle on this territory. The previous residents were then released back onto the territory, and the … resident always won this time. The convention is that … always win the contest, even if the intruder was a previous resident.
intruders, new, resident
Why is this?
Sun patches are a very low value resource as they are ephemeral, so it is not worth wasting energy resources fighting for it.
read handout for lecture 9
goop
Another “game” is the rock-paper-scissors game, which has a … dynamic consisting of 3 strategies. No single strategy … is possible. The ESS for this game is for…
cyclical, ESS, everyone to play rock, paper and scissors with equal frequency
There are two possible ways in which this ESS can be achieved:
- Everyone has an equal probability of playing each strategy at any one time
- Time lag in payoffs of playing particular strategies (cyclical dynamics, where majority play rock, then scissors, then paper etc.)
An example of a rock-paper-scissors game in nature is in side-blotched lizards. There are 3 male mating strategies:
- Large territory holders: … throat
- …: yellow striped throat
- Defenders: … throat
orange, sneakers, blue
Large territory holders are … and hold a large territory that typically has several … living within it.
Sneaker males mimic … and enter large territories for sneaky matings.
Defenders defend … territories with … … … and, because they are only defending this, they are very good at detecting ….
aggressive, females, females, small, one single female, sneakers
The frequency of each morph of male over a succession of years was recorded by Sinervo and Lively (1996), and they found that the population started from a high frequency of … … in one year, but these individuals are susceptible to … … …, so the following year these were most common. These are susceptible to … … … so the following year there was a higher proportion of these, and the following year after that there were more … etc.. This was followed for two whole cycles, showing the cyclical dynamics of this rock-paper-scissors system.
blue defenders, large territory holders, yellow striped sneakers, defenders
Mathematics provides … … about how evolution works.
general rules (that can be applied expansively)
Mating system classification encompasses:
- … behaviour
- … organisation
- … care system
- … for mates
copulation (e.g. how many mating partners an individual has), social, parental (neither? both? Just F? Just M?), competition (e.g. level of)
What are the main 4 types of mating system?
Monogamy
Polygyny
Polyandry
Promiscuity (Polygynandry)
Monogamy =
one male and one female breed (long or short term)
Most (~85-90%) …, a few … and a few … are monogamous
birds, mammals, fish (e.g. clownfish live with m and f in an anemone)
Male clownfish are smaller than females as….
females carry the eggs, and the larger a female is, the larger the clutch of eggs she can produce is. There is not this same size relationship with male sperm so size isn’t limiting fecundity.
- all clownfish start off as males and change sex when they reach a certain size
<25% of … monogamous birds are also … monogamous
socially, genetically
- fulmars have no extra-pair copulations
- but in splendid fairy wrens, around 70% of offspring in a nest are fathered by a male other than the one that is looking after them
Polygyny =
1 male and >1 female
Polygyny is present in most … but few ….
mammals, birds
Can be … polygyny, where a single male defends a … that encompasses multiples females, so he breeds with multiple females during the same time.
simultaneous, territory
- e.g. red-winged blackbird
Can be …/… polygyny, where a male associates briefly with one female, then moves onto another, then another etc.
successive, sequential
- e.g. orangutan
Polyandry =
1 female and >1 male
- present in few birds, fish and mammals
E.g. of simultaneous polyandry is in the … …
e.g. of sequential polyandry is in the … …
painted snipe (female defends territory encompassing 4-5 male territories. She lays clutch of eggs for each of these males and he looks after offspring)
spotted sandpiper
Polyandrous species are often characterised by a phenomenon known as “… … …”
sex role reversal
- females compete with other females for access to males, females often larger and brightly coloured and display
- males more cryptic as look after young and not as competitive
Promiscuity =
> 1 female and >1 male
Promiscuity is present in few … and …, but many …, … and ….
birds, mammals, fish, reptiles, amphibians
Mating system often varies within a …
species - not fixed for every member of a population, or even for the same member throughout their lifetime
e.g. extra pair paternity in monogamous species
Dunnocks: around 1/3 of females breed …, about 1/4 breed …, about 40% are…
monogamously, polygynously (male defends territory for 2 females), polyandrous or polygynandrous
Humans thought of as …, although we are more often … …, sometimes … …/…
monogamous, sequentially polygynous, simultaneously polygynous (e.g. mormons in parts of America)/polyandrous (e.g. in some areas of Tibet typical to marry multiple brothers)
Difference between males and females is in their … into …. So males have much higher … … than females.
investment, gametes (size and number of), reproductive potential
In order to maximise reproductive success, males are limited by access to …. Females are limited by access to …
females, resources (as they can usually guarantee fertilisation by a male)
… (e.g. resource distribution) –> … dispersion –> … dispersion
There are other links that can be drawn. For example, males can get females by controlling ….
Ecology, female, male, resources (e.g. resource defence)
- the latter two determine the mating system
…-… bats show resource defence - males construct and defend noosing tents which house … of females. The sex ratio in these is 1 M : …-… F
tent-making, harems, 1-37
Ecology: comparative study of mammalian mating systems. In mammals … parental care is rare. Female …. by males, and hence mating system, depends on female … size and female … size.
male, monopolisation, group, range
Clutton-Brock (1989) classified animals by their female … and … size and their … ….
group, range, mating system
Solitary females with relatively small ranges that are defendable by males (… of mammal species):
When females occupy smaller ranges it is possible for a single male to defend those ranges - mating system becomes … - common in many small mammals such as … and ….
When females occupy larger ranges then males are only able to defend a single female territory, so … arises - found in … but is relatively rare
60%, polygynous, voles, otters
monogamy, gibbons (and some other primates)
When females are solitary but have wider ranges that are not defendable by males (often the case in … where they have to keep moving to obtain enough food from patchily distributed … trees) males travel around their very large range searching for females in …, defending her from other males until her egg/s has/have been fertilised, at which point he searches for another female - e.g. in …. This is known as … … polygyny.
rainforests, fruiting, oestrus, orang-utans, scramble competition
When females are social but have ranges defendable by males:
If females are found in small groups then you often find …-… … (e.g. in colobus monkeys)
If females are found in larger groups you often find …-… … (e.g. in lions)
uni-male polygyny, multi-male polygyny
In social females that cover large ranges not defendable by males, males may … in … when competition for females in intense. In these …, they … to females and the females visit them to get sperm to fertilise their eggs with - … territories contain no resources except … themselves.
Some of the most extreme examples of … … are found in these mating systems (e.g. topi and Uganda kobs)
( … and … of … in birds).
aggregate, leks, leks, display, lek, males, sexual selection, peacocks, birds, paradise
Lek mating systems are more common the…
larger the female range is
- monogamy more common the smaller the range is
- shown in lekking antelope species as well as grouse species
So Clutton-Brock has convincingly shown that … dispersion depends on … dispersion
male, female
- though link between female dispersion and ecology less strong
Blue-headed wrasse (fish) start off as … and become … once they reach a certain size. This is because … defend sites in which they can reproduce with females. Males need to be … and … in order to get any matings at all. Females … over large, … ranges, and spawn … at predictable, favoured sites. Males cannot defend …, but can instead defend … ….
female, male (opposite to anemone fish), males, large, aggressive, forage, overlapping, daily, females, spawning sites
Warner (1990) removed male blue-headed wrasses, replacing them with new males. In a second experiment he did the same with females. What did he find?
When males were replaced, females were still present and continued to visit the same spawning sites, so 22/24 sites were still used, and no new sites were used.
However, when females were replaced, 11 of the sites were lost and 10 new ones were used by males who shifted (as the females didn’t kn`ow where the previous sites were)
Warner’s study is evidence that when females stay in the same place, males continue to remain where the females are, whereas when new sites emerged and females moved to them the males followed.
Still not really showing how ecology changes affect female dispersion and subsequently male dispersion is it?
A more convincing study that shows this is a study into the …-… vole.
Experiment 1: Female ranges encompassed by range of several males (6F, 3M competing for access to mate). Small patches of … were put out. Found that female ranges … together around these food sources - … distribution determines female dispersion. But … also converged on this food (may be concentrating activity because of … or because of …). To distinguish between these two possibilities:
Experiment 2: He moved females around separate cages (so …-… ranges), and found that single (…-…) males tended to focus on a particular female that covered quite an extensive range. When female ranges did overlap, again males tend to … around females. Therefore, female dispersion determines male dispersion.
Experiment 3: … put in small cages and moved them around; females were radio-tracked. Females were found to be … in male dispersion or activity.
Therefore female distribution is motivated by access to food (resources/ecological factors) and male dispersion is motivated by access to females.
grey-sided, food, collapsed, food, males, food, females
non-overlapping, radio-tracked, collapse
males, uninterested
Reproductive potential of males is not always …. Males have a much higher reproductive potential, but on average a male’s reproductive … is … … … that of females. This means that there is a lot more … in reproductive success among males (e.g. in elephant seals with beachmasters monopolising vs unsuccessful males). There is likely to be … between the males but also likely to be … between males and females
realised, success, the same as, variance, conflict, conflict
reproductive success of male and female … is equal, so male reproductive potential is not realised. One of few animals where male can be certain offspring are his own.
seahorse - male gives birth
Male reproductive potential is also not realised when males provide … … as must invest time and energy into … rather than …. This is particularly common among ….
parental care, offspring, mating, birds
If you are a female penguin raising young, the care provided by a male is really valuable to you. You are not simply interested in resources, but also males (who can provide more resources). The male becomes an important criterion in female behaviour. In these circumstances, females should be interested in … … to maximise reproductive success.
male dispersion
see pic on phone
Model we used for mammals works because…
very few male mammals provide parental care
Males ‘prefer’ … (as it would maximise reproductive success). Females, on the other hand, may ‘prefer’ … if they get more/better resources (e.g. paternal care). In many species, … occurs as a compromise between the conflicting interests of the sexes.
polygyny, polyandry, monogamy
For example, yellow-bellied marmot harem size varies between males having … females. In smaller groups (with fewer females), … produce more offspring. In larger groups, … produce more offspring. The best option for a female is clearly to be …, as they get more care from the male. The best option for a male is a … …, as he will produce many more offspring. There is a conflict in ideal harem size between males and females. Sometimes males win out, other times females do.
1-6, females, males, monogamous (sole female within a male’s harem), large harem
In … beetles (Nicrophorus species), a female and a male make a nest contains a …, and then care for offspring. Males attempt to attract additional females using … and females (which are …) try to prevent them from doing so. Female … … occurs in this species.
burying, corpse (e.g. bird or mammal), pheromones, larger, enforced monogamy
- males are much more likely to have additional matings if female is experimentally tethered
“…” assist breeders to raise offspring that are (usually) … … ….
helpers, not their own
Cooperative breeding is found in … of bird species, … of mammal species (e.g. mongooses, some cats and dogs), described in >10 … species and in “primitive” … ….
4-9%, 3%, fish (e.g. some cichlid fish), social insects
- varies slightly depending on how you define cooperative breeding
Among birds and mammals, the majority of cooperative breeding systems can be described as “…-…-…-…” systems (around 80% of systems). These are characterised by species such as the Florida … …, where one pair has, on average, … helpers, which feed the young and protect them from predators, and are usually … to the breeding pair.
helper-at-the-nest, scrub jay, 1.8, related (typically offspring from previous roosts who have stayed on the territory)
Another example of this type of system in mammals is the …-… …, where a breeding pair typically has 1-3 helpers, who go out hunting and help … food to pups and to the … ….
sliver-backed jackal, regurgitate, lactating female
The most extreme example of the helper-at-the-nest system among mammals or birds is in … … …, who’s social system has a degree of sophistication that has been likened to … …. They have … with reproductive division of labour. There is a … who sits in her central chamber with young, some individuals who act as … who fight off intruders, and other individuals who go foraging for food. Colonies house … individuals, but only have a single reproductive female.
naked mole rats, eusocial insects, castes, queen, soldiers, 80-100
Different behaviours in mole rats may just be…
age-related specialisations - so may not be technically eusocial. Still a very sophisticated level of cooperation exhibited.
Another type of cooperative breeding system is that which has “… breeders”. Several males and females … a nest and raise a … brood. For example the banded …, which has … in a group with several reproducing females
plural, share, communal, mongoose, 4-40
An avian analogue of this is the acorn …, which has 2-14 in a group of often … and …. A typical group has 1-4 breeding males, 1-4 breeding females and up to 8 …-… helpers
woodpecker, brothers, sisters (not the pairs who are breeding - their siblings come and help out) , non-breeding
There is quite a diversity of … social systems, more than described above.
cooperative
The most successfully theory that explains cooperative breeding (so far) is the … … … (Emlen 1982).
Ecological Constraints Hypothesis
The Ecological Constraints Hypothesis suggests that (preferable) … breeding can be constrained by ecology, e.g. due to habitat … or lack of available key resources. This causes some individuals to delay dispersal and stay on their … … (where they were born and raised). The … benefits of helping their relatives may then exceed those of not helping.
independent, saturation, natal territory, fitness
What is the assumption of ECH?
There is a better fitness return from breeding than helping, but breeding is constrained (so helping becomes the next best option in terms of fitness)
There is good evidence for this in many species, for example …-… …, which are cooperative breeders, produce, on average, 0.5 genetic equivalents by breeding but only … by helping.
long-tailed tits, 0.14
… evidence for the hypothesis that “constraints cause offspring to delay dispersal instead of breeding independently”: e.g. in acorn woodpeckers…
Correlational, worse years in terms of acorn crop size led to more helping (a higher percentage of individuals delayed dispersal).
- however is just a correlation and not necessarily causal (i.e. acorns don’t necessarily cause woodpeckers to help rather than independently breed - may be other factors affecting acorns such as climate)
In order to establish a causal relationship between x and y, one must…
carry out an experiment with controlled and manipulated variables
Experimental evidence for the hypothesis that “constraints cause offspring to delay dispersal instead of breeding independently”: e.g. in superb fairy-wrens (coop breeder from Australia), … of pairs have male helpers. Helpers are always male, as the sex ratio is 1.8 males: 1 female. The limited mating females in the population means that many males can’t find a mate and…
Experiment 1: Male removed from breeding pair (of 33 pairs) - left 33 vacancies for 33 helpers. …/33 were filled by helpers (within 5hrs). So helpers are capable of … when the opportunity arises.
Experiment 2: Male and female removed, leaving 7 empty territories. None of these were occupied by helpers (so get some benefit from staying and helping rather than dispersing to find habitat). After 3 days, the … were released back onto the vacant territory and …/7 vacancies were filled.
This experiment shows that:
- helpers are capable of …
- habitat is … (ecological constraints hypothesis)
- … are limiting
60%, benefit more (in terms of fitness) from helping their mothers raise offspring.
31, reproduction
females, 7
reproduction, limiting, mates
- experiment by Pruett-Jones and Lewis (1990)
Red-cockaded woodpecker: Limited by … …, which take several years to excavate (by pecking wood). Creating artificial nesting sites led to…
helpers dispersing to fill these sites
Walters et al. 1992
How do the fitness benefits of helping exceed those of not helping? Care is costly, so why don’t individuals forage for only themselves while they wait for an opportunity to breed independently? There are two ways helpers can benefit from helping:
- direct fitness and indirect fitness
Direct fitness is fitness gained from … reproduction. Indirect fitness is fitness gained from increasing production of …-… … (via … selection). Together these make up … ….
personal, non-descendant kin, kin, inclusive fitness
What are the direct fitness benefits of helping?
- Increased survival due to the benefits of group living, e.g. increased vigilance and ability to find food, dilution effect (group augmentation hypothesis - better to live in a large group so fitness can be increased by contributing to make the group larger) - white-winged choughs even kidnap offspring from other groups, by luring them with food, who can subsequently become helpers. Shows benefits to increasing group size even by having to look after non-kin members.
+ cichlid groups are more likely to accept immigrants when predation risk is high - Increased probability of future breeding (e.g. by territory inheritance - in Florida scrub jays 48% of helpers eventually acquire all or part of parental territory - or increased probability of mate acquisition - in pied kingfishers there are two types of helpers (primary close kin vs secondary distant/non-kin), 41% of secondary helpers “inherited” the female when the breeding male died, and 18% ousted the breeding male - or increased experience (skills hypothesis) - e.g. become better parent in future - Seychelles warblers who helped produce more fledglings that are more likely to hatch)
- Direct reproduction - helpers are usually female - 44% lay eggs in helped nest - 15% of all young produced by “helpers” who have layed eggs in nest, probably after sneaking copulations with males from other groups (to avoid inbreeding)
What are the indirect fitness benefits of helping?
- Increased reproductive success of relatives. E.g. long-tailed tit and white-fronted bee-eater reproductive success increases with number of helpers (due to reaching a larger size by gaining more food) - again correlation not necessarily causal (perhaps higher quality pairs on better territory gain more helpers).
Experiments of Florida scrub jays and grey-crowned babblers have shown decreased reproductive success with decreased group size (moorhens showed no difference though) - Increased survival of related breeders by “load-lightening” - reproduction and parental care care costly - helpers reduce these costs. Observational data does support this notion - acorn woodpeckers and dwarf mongooses show greater breeder survival in larger groups - again correlational and are other benefits to living in a group than help from helpers so not necessarily load-lightening that is causing this difference
