Midterm 2 Flashcards
Adaptation
- short term change within a species (aka microevolution); example moth wings change colour
Evolution
Long term changes that results in the appearance of new species (aka macro evolution)
Natural selection
How species change over time
- the primary mechanism of biological change over time (adaptation and evolution)
- proposed by Darwin
- the differential survival and reproductive success in each parental generation which leads to a change in frequency of traits from one generation to the next (adaptation/ evolution)
Natural selection 3 fundamental Observable facts
- variation
- inheritance
- overproduction
Variation from..
- random mutations
- random genetic recombination
- non- random mate choice
Inheritance
- Variation passed from parents to offspring
- principles not known when Darwin wrote “on the Orion of species”
Overproduction
- there are always more offspring born that can or do survive to adulthood (competition)
Who survives to adulthood?
- those who happen to have variation (morphology or behaviour) that helps them survive
- the environment naturally selects some variants over others
Important point to understanding evolution by natural selection:
- not survival alone but survival and reproduction
Fitness
- An individual’s ability to reproduce successfully compared to other members of the same species
- Low fitness= low reproductive success
- high fitness = high reproductive success
How does natural selection work?
- traits possessed by individuals with high survival and reproductive success will be passed to future generations at higher rates
- the environment naturally selects some variations over others to survive and reproduce
- the population over time becomes better adapted to local environments
A change in the frequency of traits from one generation to the next
Adaptation/ evolution
Traits that are well suited to the environment..
- give individuals an advantage in survival and reproductive success
- will appear in increased frequency in future generations
The traits that are not well suited to the environment..
- put individuals at a disadvantage in survival and reproductive success
- will appear in decreased frequency in future generations
Peppered moth
- example of natural selection producing adaptation
4 points about natural selection (peppered moth demonstrates):
- Evolution (change) operates on the population- no individual moth ever changed colour. Individuals do not “evolve”
- Natural selection operates in the individual. Individuals survive and reproduce or not
- Variation had to be there in the first place
- There is no such thing as an absolutely better variant- depends on the environment
Sociobiology (developed in 1960s and 1970s)
- applying evolutionary principles, specifically natural selection, to behaviour
- trying to understand how behaviour might be naturally selected/ adapted/ evolved
- asking how behavioural variations give individuals an advantage in survival and reproduction
3 main components of sociobiology
- Kin selection
- Reciprocal altruism
- Parental investment
Popular definition of altruism
Helping and selfless behaviour; opposite if selfish behaviour
Biological definition of altruism
- behaviour that potentially improves the survival and reproductive success of the recipient while potentially endangering the actor
Altruism examples
- predator alarm calls
- defending a group member from a predator
- helping another individual in a fight (coalition)
- feeding/ caring for an infant
Why is altruism hard to explain ?
- natural selection states the behaviour that increases the survival and reproductive success of the actor will be passed on at a higher rate to next generation and
- behaviour that decreases the survival and reproductive success of the actor will not
Group selection
- originally altruistic behaviour was thought to evolve because it was for the good of the group
Problem with group selection- Wynne- Edwards 1962
- defined as natural selection acting in the group rather than the individual
- for it to work, groups with altruists would have to have higher fitness that those without (but altruists may have decreased RS, while selfish individual would have better RS)
- the altruists wouldn’t be passing on their genes
- rejected: natural selection only makes sense if it acts on the individual (each individual striving to maximize own reproductive success)
What questions was the origin of sociobiology?
“how could altruism have evolved?”
Altruism evolved not by ___, but by _____
Not by group selection, but by kin selection
Kin selection: based on recognition that…
- Each individual shares generic material with their relatives
- Even if you never reproduce, it is possible to have some of your genes represented in the next generation if your relatives are reproductively successful (helping inclusive fitness by helping kin)
Natural selection can operate on ___ rather than individuals
Genes
Inclusive fitness
Individual fitness plus the effect upon the fitness of relatives
Hamiltons rule
c< bxr
1) the cost (c) to the actors fitness
2) the benefit (b) to the recipients individual fitness
3) the degree of relatedness (r) between the actor and the recipient (the proportion of genes shared by common descent)
Does altruism ever occur between non-relatives?
Yes- cannot be explained by kin selection, alternative explanation proposed is reciprocal altruism
Reciprocal Altruism (Trivers 1971)
- helping behaviour between non relatives
- individuals help others so that they will get help in the future when they need it, individuals will cease to help “cheaters”
2 requirements for reciprocal altruism
1) sociality: individuals must have the opportunity for repeated interactions
2) “helping” individuals are of similar abilities (rank, size, etc.)
Does “helping” behaviour ever occur between non-kin without evidence of reciprocal altruism?
Yes- these types of behaviours could also evolve through mutualism
Mutualism
- interaction between two organisms where each gains a fitness benefit
- these interactions can look like co/operation (or bee pollinating flower, males in coalition)
- not altruism because there is no overall cost to the actor helping
Natural selection operates on
Individual & genes
Evolution acts on the
Population
Grooming between two un-relayed females of similar rank is best explained by:
Reciprocal altruism
Sexual selection
- mechanism proposed by Darwin to explain secondary sex characteristics
- realized that some traits possessed by (mostly) males were impossible to explain with natural selection
- instead of aiding males in survival, these traits seemed detrimental
Secondary sexual characteristics
- features of sexual dimorphism
- male/ female distinctions that appear at puberty and go beyond basic reproductive differences
- examples: differences in size, coloration, weaponry, shape, ornamentation.
Sexual dimorphism examples among mammals
- peacock
- birds of paradise
- deer
- lions
- Irish elk (antlers)
Sexual dimorphism primate specific examples
- hamadryads (canines)
- geladas (red chest)
- uakaris (red face?)
Why was another mechanism needed to explain secondary sexual characteristics?
- They are not easily explained by natural selection (not apparently beneficial, and sometimes even detrimental, to survival
- They do not appear until adulthood
According to Darwin, there are two mechanisms leading to the evolution of secondary sexual characteristics:
- Male- male competition
2. Female mate choice
While secondary sex characteristics do not provide ___, they can give males a _______ advantage
Do not provide survival advantage, can give males reproductive advantage
Male male competition
- intra- sexual selection
- secondary sexual characteristics give males a reproductive advantage through competition. With other males
Types of Male- male competition (Anderson 1994)
- Contests- physical attacks or threats
- Scrambles- early search & detection if females that determines the order of contact
- Endurance rivalry- time and energy spent seeking, attracting, and defending mates, as well as being reproductively active
Female choice
- inter- sexual selection
- secondary sexual characteristics give males a reproductive advantage by making them more attractive to females
“Good genes” models
“-Handicap” models
- “viability indicator” models
“Handicap” models
- purpose that ornamentation reduces average male survival, enabling females to assess individual males ability to survive despite his burdensome ornament
Viability indicators
- females asses male characters because they specifically indicate a secondary less apparent trait determining male fitness
- examples testosterone levels, parasite load, body size, fighting ability, age, tenure stage
Sexually selected traits
- behavioural displays
- acoustic displays
- ornaments
- weapons
- pelage/ plumage
- skin coloration
- chemical signals
Behavioural Displays as indicators
- stiff leg display- colobus monkeys
- males vary in expression of these behaviours (ex high ranking males display more than low ranking males)
- male displays decreases in vigorous over time
- displays were targeted to other groups and males
Acoustic displays as indicators- wahoo
Wahoo - Yellow baboons
- rate and duration are correlated with a males competitive ability. High ranking males:
- call more often and at faster rates
- call for longer bouts
- give wahoos with higher fundamental frequencies (FO)
- give longer ‘hoo’ syllables
- FO decline, hoo syllables shortened and forming dispersion decreases
with age
- the acoustic features of contest wahoos thus potentially allow listeners to assess a males competitive ability
Acoustic displays penguins
- the pitch of male defeats is calls in little blue penguins indicates male body size and likeliness to respond vocally to nest intrusions
- nests defended by larger males produced eggs and chicks earlier and the chicks grew more quickly
Acoustic displays dark eyes juncos
- testosterone (T) mediated male display
- T- implanted males sang more long- range songs at higher rates & occupied larger home ranges
- females preferred T- implanted males
Ornaments as indicators
- Blue Testes- Vervets: vividness of coloration represents male quality and predicts outcomes if aggressive encounters
- throat sac and cheek pouches- orangutans: function in M-M competition (female choice is secondary)
- call transmission and reflection
Weaponry as indicators
Teeth- mandrills - canine dimorphism and size for infra- male competition
Pelagic/ plumage as indicators
- colourful North American Passerines: in birds male plumage brightness and song quality is reduced by parasite infections
- Indian peafowl: long tail requires energy to maintain
- long train is an indicator of good body condition
Skin coloration as indicators: Geladas
Chest patch
- males with redder chests were higher quality:
1) leader males- the only males with reproductive access to females had the reddest chests
2) within leader males, males with larger units (>6 females) had redder chests than males with small units
Skin Coloration Uakari
- lack of pigmentation and intricate capillary system
- red head if uakari monkeys fade when they are ill
Skin coloration- rhesus macaque
Rhesus macaque - skin becomes bright red during the mating system with fluctuation in hormones
- evidence for female choice of more vivid skin
Coloration and condition- mandrills
- rump
- consistent through our t year
- vivid colattion indicates quality
- fatted rump is an honest indicator o condition- female choice
Chemical signals as indicators
- meadow voles
- scent marking is a form of male competition where females prefer to mate with the male that marked the spot last
- finding another males mark and counter marking takes time and energy
- the male displays his vigour and persistence
Testosterone (T)
- T- level related to male success in agnostic competition
- T- suppresses immune system
- so males that can maintain ornaments and displays that are mediated by T, without getting sick, show their superiority
- the strength of the males immune function could be heritable, so the females offspring could benefit
Sexual selection is difficult to study in primates
- they live a long time and reproduce slowly (determine their lifetime reproductive success could take 20 or more years)
- long term social relationships occur: hard to defensive why a female prefers a male
- males often use sexual coercion to mate with females (male may not be preferred but female mates with him anyways)
Parental investment (Trivers 1972)
- about explaining sex differences in behaviour (& morphology)
- reformulation of darwins theory of sexual selection
- any investment by the parent in an individual offspring that increases the offsprings chance of survival (and hence reproductive success) at the cost of the parents ability to invest in other offspring
- “the relative parental investment of the sexed in their young is the key variable controlling sexual selection”
Assumption of parental investment
- that we have limited time and resources
Parental investment: great potential for conflict and competition between:
- Parents and offspring (weaning conflict)
- Successive offspring (sibling rivalry for attention/ care)
- Parents (battle of the sexes)
3 reasons that male and female reproductive strategies and behaviour are typically so different
- Different levels of parental investment
- Different variance in reproductive success (a.k.a. Lower potential reproductive output for females)
- Different limiting factors
Different levels of parental investment
- the different initial and then subsequent levels of parental investment leads to very different strategies for males and females
- females: quality- they choose males that will provide assistance, food territory, good genes etc.; primary care- givers
- males: quantity: go for as many fertilizations as possible and move one- little or nothing to lose; generally do not give care
Variance in reproductive success
Parental Investment: - females high - large nutrient rich egg, approximately 1 of 400, gestation & lactation
- males: Tibet sperm, 1 of approx 4 billion
Females: low inter- female variation (similar # babies); typically have X offspring (X= reproductive lifespan/ intervirth interval)
Males: higher internals variation, limited by social factors, compilation time and sperm, stakes higher for males and competitor is therefore more intense
Limiting factor for females that
Access to energetic resources
Limiting factors for males
Access to reproductive opportunities
The more similar the level of parental investment between the sexes, the ..
More similar the sexes will be in behaviour and/ or morphology
Ex: monogamy and monimorphism (owl monkey, gibbons)
Polygyny and dimorphism (hamadryads baboons)
T/F: male features used for male- male competition may also be used for female mate choice
True
T/F signals that handicap the male are not good indicators of male quality:
False
T/ F parental investment theory may explain why some women usually want to get married and some men don’t
True
T/ F Parental investment theory and good genes models may explain promiscuity
True
Reproductive success
- an individual’s genetic contribution to future generations
- the currency used to measure ‘success’ in evolutionary terms = the number of offspring an individual produces
The social organization that we observe in primate species is often said to be representative of the…
- Females napping into the food distribution
- males mapping onto the female distribution
Other than access to females, what is one limiting factor for males
- sperm depletion
Estrus
The period around ovulation where the female is able to conceive
- females can advertise the timing of their ovulation (ie hanadryas baboon- sexual swelling), but other have evolv d concealed ovulation (or white- faces capuchin)
Sexual swelling chimpanzee
- size and coloration of sexual swelling of the perineal tissue corresponds to days relative to ovulation
Sexual swelling geladas
Vesicularion and coloration of swelling of area surrounding the neck and threat area corresponds to days relative to ovulation
Meals reproductive strategies:
- male monopolization
- sexual coercion
- priority if access
- alternative male strategies
- sperm competition and cryptic female choice
Male monopolization potential depends on:
1) the number of females in the group
2) the distribution of estrus females
Asynchronous
- not at the same time
- a single male has a greater change of monopolizing access to females (ex hamadryads baboon, white faced capuxhings)
Synchronous
- at same time
- a single male has less of a chance of monopolizing females and preventing other males from having access to females
- eg “male influxes” in guenons
Sexual coercion
- use by male of force, or threat of force, that functions to increase the chances that a female will mate with him at a time when she is likely to be fertile, and to decrease the chances that she will mate with other males, at some cost to the female
Sexual dimorphism and sexual coercion
- relationships between the sexes are more likely to be characterized by sexual coercion
- example gorillas, geladas, orangutans
Sexual monomorphism and sexual coercion
- relationships between the sexes are more egalitarian; males do not have a physical advantage over females
- examples monkeys, Tito monkeys, calltrichids
Types of sexual coercion
- Infanticide
- Harassment
- Intimidation
- Mate guarding
5, mate herding - Forced copulation
Infanticide
Infant- killing by males, most extreme form of sexual coercion
- males kills infants to eliminate another males offspring and increase their own chances of mating
Harassment
Continually direction sexual solicitations, follows, and perhaps aggression towards females that are reluctant to mate
Intimidation
Aggression to receptive females that may make the female more likely to mate with that male in the future, rather than males
Mate guarding
Staying in proximity to the female and aggressively keeping other males away from her (can only be used against less dominant males)
Mate herding
Controlling female movements, to keep her away from other groups or males
Forced copulation
Forcing the female to mate when she is unwilling
Sexual Selection hypothesis for infanticide (Sarah Hrdy 1974)
- proposes that male infanticide has been selected for because it increases the performers reproductive success relative to other males
3 conditions that must be met for the sexual selection hypothesis for infanticide
1) infanticide male does not kill his own offspring
2) elimination of the offspring should shorten the inter- birth interval of the female (being female into estrus)
3) infanticide male should mate with female whose infant he killed
Priority of Access Model
Prediction: rank should lead to higher reproductive success
Observation: male mating success & paternity tend to correlate with rank in primates
When may a mother rank influence her sons rank
- in patrilineal species (ie male philopatric) ex- chimpanzees, bonobos
- in matrilocal species where sons of high ranking females chose to stay
Bonobos
- patrilineal
- females are co- dominant with males
- mothers help sons climb hierarchy
- benefits of high rank = central location
Patrilocal societies and male rank
- male rank may be influenced by the benefits of remaining with male kin: - ready coalition partners, fewer extra group males
- extrinsic (coalitions) and intrinsic (size)
- high rank = high reproductive success
- male hierarchies are not very stable
Male dispersal and male rank
- males leave natal group at sexual maturity and young males enter first group typically at bottom of hierarchy:
- lineage at birth not influence adult rank
- competition is usually independent
- male rank based intrinsic factors
Secondary dispersal
Male more physically mature and may challenge for alpha status
Intrinsic factors influencing male rank;
- age
- size
Weight
Fighting ability
Personality - ex baboons and Berbers dominance rank is inversely related to age
How do she graded societies form?
- one male group becomes multi male (can be patrilineal or both sexes disperse)
- fathers allow son to remain in natal group or an extra group male is allowed to join
Why do she graded societies form
- original male has ally to repel extra group males
- dominant male is usually the one that mates
Alternative male strategies
- lower ranking males can form coalitions to try and access females- guard making pair or keep high ranking male occupied or distracted
- all male bands- aids entry into new group/ gain power over males
- sneak compilations by extra group males
- friendships
Male cohorts and coalitions
- parallel dispersal: in some species males may disperse with their cohorts from their natal group and form coalitions to oust alpha male
- ex white faced capuchins
Friendship in baboons
- Lowe ranking males and females become ‘friends’:
- preferential grooming & proximity
- females usually mate with dominant male but also with her friend
- male friends protect infants from other males
- friendships end if the infant gets killed
Within group contest competition
- males fighting within the group for high dominance rank
Between group contest competition
- males fight to keep other males out of group & prevent females from having extra group compilations
Scramble competition
- sperm competition
Evidence sperm competition
- relative male testes to body size: largest in species where females mate with multiple males
- larger tested produce: greater quantities and better sperm
- example marquis
- lesser galago: males with largest tested had highest matin success
Mechanisms of sperm competition:
- volume of sperm & motility
- last male precedence
- copulatory plug
Male male competition happens at:
- copulation
Although female female competition for access to males rarely occurs, when would it?
- in species where males provide a valuable resource or service
- more likely in monogamous unit
Data evidence of food being critical resource for female reproduction
1) females in provisioned colonies higher reproductive success and shorter inter- birth intervals, younger at first reproduction
2) amenorrhea- what prevents lactating females from getting pregnant again-
Three key variable affect female feeding behaviour:
1) food quality
2) spatial distribution
3) temporal availability
Even spatial distribution:
- low quality foods
- even distribution
- not monopolizable
- indices scramble competition (first come first serve)
Clumped foodsh
- high quality
- monopolazible/ worth competition
- induce contest competition
- fruit
How to deal with seasonality:
1) change diet = switch to fallback foods
2) chance ranging/ grouping patterns to maintain high quality diet
Socio- ecological theory
- predicts that primate social organization responds in predictable ways to food abundance, distribution, and quality
- dispersal patterns, female female competition (or dominance hierarchy)
- intensity of female- female competition
Intra group
Within group
Inter
Between group
2 types of food competition
1) scramble competition
2) contest competition
Scramble competition and female relationships
- food is low quality and evenly distributed, thus not monopolizable
- no overt interactions over food
- do not form coalitions to defend food
- no discernible female hierarchies
- leads to an absence of strong bonds between females
Contest competition and female relationships
- individuals cannot always compete because it is dangerous and energetically expensive
- establishment of dominance relationships greatly reduced fighting and stress within group and keeps peace
- strong social bonding for coalitionary partners
Egalitarian
- no dominance hierarchy
Nepotistic
Dominance hierarchy based on kinship
Despotic
Clearly established, linear dominance hierarchy
Tolerant
- dominance relationships exist but dominants are tolerant of subordinates and reversals may occur
