Part 1 - non-kin Flashcards
In this module, we’ll be mainly using the … approach to animal behaviour
adaptationist
- equavilent to functional approach (defined by tinbergen)
Starting assumption: behaviours, like any other trait, are the product of…
natural selection - adaptations that allow organisms to survive and reproduce better than if they lacked those traits.
Social organisation of weavers:
Cassin’s Malimbe is brightly coloured, generally breeds in … … - pair and build a nest together to raise offspring.
Grey-capped social weavers breed in … ….
Black-headed weavers breed in …; each male makes a nest and tries to attract a female. Nests are aggregated into large … with dozens to hundreds of nests within a single tree. The males are much more brightly coloured than the females.
Sociable weavers build extraordinary nest structures which can weigh several tonnes and house hundreds of pairs, and can last decades. Within these communal structures, each pair makes their own … …. Very little sexual dimorphism.
solitary territories,
small colonies (clusters of nests)
pairs, clusters
nesting chamber
How do we make sense of this diversity in weavers?
Understanding the rules and patterns observed across the species.
The first person to tackle this problem in an adaptationist way was … …
John Crook (1964) - early days of behavioural ecology
Asking questions such as why are some weavers solitary and others colonial, why are some dimorphic and others monomorphic?
John Crook went through all the studied weaver species and classified them according to their…
degree of sociality and the kind of pair bond that they had, in addition to their degree of dimorphism. He also recorded ecological features such as the habitat in which they lived, their diet etc.
He found some very consistent patterns that explained the degree of sociality and kind of pair bond. The percentage of species living in forests that are solitary is very …, where as the percentage of grassland (e.g., … …) species that are solitary is very ….
Likewise, monogamy was far … common in forests than grassland.
high (90%), sociable weaver, low (6%), more (100% vs 6%)
- (polygyny more common in grassland)
He observed some very consistent patterns that explained the degree of sociality and kind of pair bond. The percentage of species living in forests that are solitary is very …, where as the percentage of grassland (e.g., … …) species that are solitary is very ….
Likewise, monogamy was far … common in forests than grassland.
high (90%), sociable weaver, low (6%), more (100% vs 6%)
- (polygyny more common in grassland)
Crook was able to test the hypothesis that social structure and degree of sexual selection was a function of … ….
- now know this is a very general pattern - long-tailed macaques live in very large groups and are primarily seed/fruit eaters, colobus monkeys live in relatively small groups that are leaf/fruit eating, golden lion tamarin monkeys primarily live in pairs (sometimes with helpers) and feed primarily on insects. Rules apply across different … groups (… approach)
food distribution
taxonomic, comparative
Problems with comparative approach:
- phylogenetic …. Two species may share a particular behavioural trait not because they occupy similar ecological niches, but because they are closely related. This must be controlled for - tools to do so are now very powerful.
relatedness
An alternative approach to the comparative one (comparing taxa) is to ask questions about … variation - why do … vary in morphology or behaviour. What are the causes and fitness consequences of this variation?
individual, individuals
e.g. a wading bird called a … is a … species. Males gather in small groups and display to visiting females, who choose a single male to mate with and then leave them to look after the offspring. Males have large … around their heads that they use to display to females. Some males are very successful and can monopolise matings within groups. What is it about these individuals that makes them attractive compared to other males.
There are also … males who occupy the fringes of the group trying to sneak copulations with females as they come and go.
Some males also … …, and do not grow a ….
ruff, lekking, plumes, satellite, mimic females, plume (again sneak copulations)
We can look at how successful different strategies are at increasing the … of … expressing them.
- can be used to explain seemingly counterintuitive behaviours such as infanticide and sexual cannibalism.
fitness, individuals
So comparative analysis looks at … variation and study of individuals looks at … variation
interspecific, intraspecific
Long-term studies of … individuals are particularly valuable when studying intraspecific variation, and have been important in the development of evolutionary theory.
There are drawbacks
- difficult to get long-term funding (tends to only work in 3 year packages - can’t ask to fund 50 yr elephant study)
- Takes a long time to get data and results, particularly for long-lived species such as red deer, elephants or humans.
marked (can follow throughout lifespan, how many offspring, survival rates of individuals following different strategies etc.),
An alternative approach is to conduct … studies in the field or lab. Often short-term and do not require natural variation across lifetimes to determine why animals behave the way they do. Instead, certain traits are …, and the … of these on individual fitness are studied.
experimental, manipulated, consequences
E.g. male long-tailed widowbirds have enormous tail …. The length of these tails were manipulated to test the hypothesis that these tails were the product of … … (longer tailed males more attractive to females than shorter tailed males).
plumes, sexual selection
What was done to the control males?
Feathers cut off then reattached at the same length
Found that…
number of nests attracted by males varied in relation to the manipulation: longer tails = more nests.
Lab experiments have the benefit that they are often much more … than in the field, and results are often obtained much ….
controlled, quicker (e.g. drosophila or microbes that reproduce very quickly)
The adaptationist approach:
- comparative analysis - interspecific variation
- study of individuals - intraspecific variation
- observations in field/ lab
- experimental studies in field/lab
Relies on evolutionary theory - testing predictions and hypotheses derived from evolutionary theory - sound theoretical basis allows us to propose hypotheses that we can go out and test - scientific method.
Key thinkers in development of evolutionary theory:
- Darwin (1850s-1870s)
- Fisher (1930s-1940s)
- Maynard-Smith (1960s-1990s)
- Hamilton (1960s-1990s)
- Trivers (1970s)
- Dawkins (1970s-2000s)
Bunch of ledges.
The adaptationist approach is to study behaviour and ecology of individuals and species all founded on sound evolutionary theoretical principles which allow us to test hypotheses.
Weigh up the … and … of a behaviour to determine its … …, i.e. what is the evolutionary value (…) of a particular trait - why has it evolved?
costs, benefits, adaptive significance, function
What biological unit does natural selection act upon?
Natural selection acts on … to produce organisms that are designed to maximise their fitness
The gene or the individual
- individuals survive, reproduce and die, but the consequence is the gene frequencies in the population change through time
genes
This means that individuals and their genes are expected to behave ….
selfishly (to maximise lifetime reproductive success)
- maximise number of copies/offspring in next generation
So genes are going to be in conflict with other alleles on the same locus, and individuals will be in conflict with other individuals to maximise LRS. Natural selections makes conflict ….
inevitable
Group selection doesn’t work because it is vulnerable to….
exploitation by selfish individuals.
Conflict is … - inter- and intra-specific. It is also rife within related families. e.g. males compete with other males for females and females compete with other females; males and their female partners are in sexual conflict over investment in offspring; offspring are in conflict with their parents over how much their parents should invest in them; and offspring (siblings) are in conflict with each other over their share of the parental care.
ubiquitous
It is expected that we see selfishless and conflict everywhere within nature. But … is also rife in nature, within and even between species* - however, it tends to be … in evolutionary terms.
cooperation, unstable (e.g. vulnerable to exploitation)
*e.g. fish and cleaner shrimp (cleans gill rakers and removes parasites)
The … … game is used to demonstrate the instability of cooperative behaviour:
A group of individuals all contribute to a public good, e.g. taxes. Everyone benefits from the public good (provision of resources and services). There may be selfish individuals in the population who do not contribute to the public good yet still gain the benefits. This creates a social dilemma, as groups of cooperators out-compete non-cooperators outside of the group, yet within the group, non-cooperators will do better than cooperators. There will always be the temptation to defect in any cooperative endeavour.
public goods
Hardin described this dilemma as the … … … …. He used the analogy of livestock owners exploiting the common land. When there are shared benefits or a ‘public good’ that individuals contribute to, there will be a temptation to cheat, or free-load. E.g. moorhen partners may provide a lower share of the parental care if they can get away with it.
tragedy of the commons (1968)
Sociable weavers must continuously maintain their large shared nest structure, which is essentially a … …. How is it ensured that every member of the colony contributes to this upkeep? - read van dijk et al. (2014)
common good
Adaptation is…
evolutionary change resulting from natural selection
A unit of natural selection must have the ability to survive, … and make accurate … of itself
reproduce, copies - general expectation that behaviour should be selfish rather than cooperative
Cooperative behaviour is defined as behaviour that benefits another … and that has been selected for because of its beneficial effects on the ….
individual, recipient
- the selected for part is important - cows defecating is beneficial to flies etc but it hasn’t been selected for because of this benefit but for other reasons
Paradox: groups composed of … out-compete groups of …, but … do better than … within groups.
cooperators, non-cooperators, non-cooperators, cooperators
- tragedy of the commons
Theoretically, … usually replaces …, so the tragedy results in social ….
selfishness, cooperation, collapse
- however the common existence of cooperative behaviour demonstrates that the tragedy is not inevitable and mechanisms to resolve the conflict between selfish interests and social cooperation must be widespread in nature
Who (wrongly?) proposed that “it was an evolutionary emphasis on cooperation instead of competition in the Darwinian sense that made for the success of the species, including the human”, using philosophical and social arguments but providing no evolutionary mechanisms.
Peter Kropotkin - in his book “Mutual Aid: a factor in evolution” (1902)
Who coined the term “survival of the fittest” in 1864?
Herbert Spencer
Who founded the idea of eugenics and biological determinism in 1883?
Francis Galton
In the early 1900s, whose work was rediscovered and dominated work on the mechanisms of genetics and evolution?
Mendel
When was this combined with Darwin’s work to found neo-Darwinian modern syntheses, bringing together natural selection, Mendelian genetics and population genetics?
Ronald … was a key architect of this.
1930s-40s,
Fisher (essentially a statistician applying this to biology. An important book was “genetical theory of natural selection” (1930))
Fisher recognised that traits favoured by natural selection are those that enhance … fitness, and recognised that there will be “… effects in cases in which an animal favours or impedes the survival or reproduction of its relatives” though “such indirect effects will in very many cases be unimportant compared to the effects of personal reproduction”
individual, indirect
Another key figure in the development of neo-darwinism was JBS …, who was a fan of experimental biology. He apparently quipped in a pub that he would not lay down his life for a brother, but for…
Haldane, “two brothers or eight cousins” - stated importance of relatedness in the expression of behaviour
Bill … had read extensively on Haldane’s and Fisher’s ideas and was a brilliant natural historian. He noticed social behaviour everywhere in nature. He saw that the potential for an evolutionary explanation for altruism if…
Hamilton, the level of selection was considered to be the gene rather than the individual - this will only be the case “if the affected individual is a relative of the altruist, therefore having an increased chance of carrying the gene”
- this was the first verbal expression of gene-level selection
In 1964 Hamilton used his idea of gene-level selection to propose his theory of … ….
inclusive fitness
Inclusive fitness theory:
A gene can increase transmission to the next generation by increasing the fitness of…
- the individual it is in = direct fitness
- individuals with copies of that gene = indirect fitness
inclusive fitness =
direct fitness + indirect fitness
r =
coefficient of relatedness
Fitness provided by ones own offspring only is known as…
personal fitness, or neighbour-modulated fitness
It is important to remember that inclusive fitness theory applies equally to actions whose effects on recipients are … rather than ….
negative, positive (see table in photos - e.g. selfish or spiteful behaviour)
Cooperative behaviour can be … beneficial or ….
mutually, altruistic
- altruism particularly interesting as decreases direct fitness of actor
In practice, inclusive fitness may be hard to measure (particularly …; personal fitness is much easier to measure by counting the number of offspring). We have to know how many of the actor’s offspring were attributable to the social interaction with another individual and how many of the recipients offspring can be attributable to the action of the actor, plus the relatedness of the offspring. Then indirect fitness can be quantified, and inclusive fitness can be derived. There are some good examples
indirect
Hamilton’s rule can be used to understand whether a social trait is adaptive or not. Altruism evolves if:
rb > c
rb - c > 0
r = relatedness b = benefit to recipient c = cost to actor
E.g. kin selection tested in Turkeys (Krakauer, 2005):
Males form … to court females -> … gets all matings.
So why do subordinates help if they don’t get any copulations themselves?
Relatedness among males within the coalitions is ….
The benefit to the dominant male of having subordinates (no. of offspring produced by dominant male) - (no. of offspring produced by solitary male) = …
The cost to the subordinate (no. of offspring produced by solitary male) - (no. of offspring produced by subordinate male) = …
coalitions, dominant, high (~0.42, nearly relatedness of brothers), 6.1, 0.9
So if rb - c > 0 = selected for, then…
(0. 42 x 6.1) - 0.9 = 1.7
1. 7 > 0 so cost of helping is outweighed by kin-selected benefit
Considering how long the theory has been around, remarkably few studies have actually been published that directly test this rule.
Such a shame, very meagre
It is very difficult tbf
Solutions to the difficulty of quantifying inclusive fitness e.g. using … for fitness such as productivity of …, not those who survive to adulthood, in a lifetime; … of productivity e.g. single season reproductive attempt, offspring condition or mating success; survival across a … time interval; or energy budget/food intake
proxies, offspring, snapshots, discrete
The evolution of life on earth entails a series of major transitions in complexity, e.g. the origin of chromosomes, the origin of eukaryotes, the origin of sex etc. Look more closely at origin of … and origin of … …. Also origin of human society/language. Each of these transitions involves …, so social evolution theory explains each transition using the logic of inclusive fitness theory
multicellularity, social groups, cooperation