Final Exam - Psych 3T03

Strategic sperm allocation

ejaculations are costly and finite, so males distribute sperm stores differently based on competition

Strategic sperm allocation - humans

males viewing images of rivals (competition) had more motiel sperm

Strategic sperm allocation - european bitterling

males ejaculate more often when rivals are present

Mate choice for direct benefits

something tangible like male resources or male parental ability or both

Direct benefits - male resources

nuptial gifts, bullfrog territory, harrier hawk courtship feeding

Direct benefits - parental ability

sculpins choose largest male, sedge warbler males with larger repertoires are better at feeding and providing care

Direct benefits - both resources and parental care

Mottled triplefin, larger male = more rocks and more time spend guarding

Mate choice for indirect benefits

genetic quality of father influences offspring quality

Indirect benefits - African red-collared windowbird

male tail is an impediment (drag, predation) thus costly signal. females prefer long-tailed males

Indirect benefits - song sparrow

females prefer males with larger repertoire because they have more independent (fledgling) and breeding offspring + grandoffspring

Indirect benefits - bowerbird

males build display nests for courtship, success increases with display intensity

Cryptic female choice

females influence fertilization success through post-copulatory control of fertilization

Cryptic female choice - domestic chicken

differential ejection of sperm where female seject sperm of subordinate males. Also, if a male’s status went up, their sperm was more liekly to be kept

Fisherian Runaway Selection Model

As some females choose traits that were initially selectively neutral (or slightly positive), these traits increase in frequency and the genes for the trait and preference become associated. Positive feedback snowballs

How to test for Fisherian runaway selection?

Test of correlation - check if genes for the daughter’s preference and son’s intensity are correlated (and increase over time)

Good Genes Model

Male traits provide females with information about male quality (i.e. if males are in good condition, they produce the trait a lot, if they’re in poor condition, they don’t as much). So, the female can use this to figure out the condition/vigour of the male. This is less about attractiveness to the opposite sex, more about increasing survivability of her young

What 3 categories of traits for the good genes model?

Good genetic complement for the female’s genes (higher heterozygosity), disease/parasite resistance, or foragign skills

Good genes - disease/parasite resistance

females benefit from choosing the most ornamented male because the ornament reveals how healthy and vigorous a male is

Disease/parasite resistance - song sparrow

females choose mates with larger repertoire size acquire mates with greater phenotypic immunity (more swelling, better immune response)

Disease/parasite resistance - peacocks

Train length correlated with immune response, and higher RS

Good genes - genetic complimentarity

females benefit from choosing genetically dissimilar dads for their offspring (self referential dissortative mating based on genetic dissimilarity)

Major histocompatibility complex

Set of cell surface proteins with a role in pathogen resistance. They are essential for acquired immune system to recognize foreign molecules in vertebrates.

Genetic complementarity - Seychelles warbelers

Males with greater diversity of MHC alleles should be in better condition and preferred by females; NO EVIDENCE of choosing males on basis of complementarity, just highest diversity. 40% of young are extrapair

Fluctuating asymmetry

deviations from bilateral symmetry caused by environmental stresses, developmental instability, and genetic problems during development

Fluctuating asymmetry in platyfishes

Females spent more time around symmetrical males, carries over when symmetry is switched

Good genes - conditions during development

females benefit from choosing the most symmetric males because the ornament shows that the male has the ability to maintain a normal developmental course under stress

Chase-away selection model

female preference evolves prior to the sexually selected trait, mutation produces a rudimentary male display trait. Female fitness declines due to their preference, so females increase thresholds, so male attraction declines and males exaggerate the trait

Sensory bias - guppies

Colouration/saturation of orange spots is determined by carotenoid ingestion. Females have affinity for orange due to machinery evolved in foraging context, but males exploited this preference by incorporating orange spots

Sensory bias - platyfish

Platyfish prefer males with artificial tails (elongated ornaments), despite the trait not existing in their species

Sensory bias hypothesis

biases in female sensory or neural systems are important in triggering sexual selection

Why does female fitness decline in chase-away model of selection?

Females are seduced to mate even when its not in their best interest, they chase away the attractiveness but that only exaggerates it

Do big brown bats prefer low or high frequency copulators? why?

Males prefer HM females but females no difference (suggests instead post-copulatory control). Maybe echolocation calls have properties of female reproductive condition

Do big brown bats prefer odours from the opposite sex?

Neither showed preferences for body odours but females preferred male’s urine

Do frequency-modulated bout calls have a role in mate attraction?

Bats prefer FMB calls vs system noise but other combinations no preference

Sexual conflict

a form of evolutionary conflict where males and females do not share interests over reproduction

Conflict over mating and parental care - dunnocks

females engage in frequent solicitation and copulation with both males because giving them both mating access influences the probability they will feed her young, improving fledgling success vs monogamous and other nests

Why do male dunnocks engage in cloacal pecking

Stimulate sperm ejection before copulation, especially if they’ve not been around her, incase she’s mated with another male

Sexual conflict - 3 examples

conflict over mating and parental care, sexually antagonistic genes, arms race between sexes

Sexual conflict - sexually antagonistic genes

Selection on one sex can interfere with the other sex’s adaptive evolution when genes are beneficial in one sex but deleterious in the other

Sexually antagonistic genes - zebra finch

Typical males have red beaks and cheek patches while female have orange beaks. Beak colour has an opposite effect on male and female reproductive success (Males with red beaks vs females with orange have more offspring)

Sexually antagonistic selection - two types

intralocus sexual conflict and interlocus sexual conflict

Intralocus sexual conflict

Alleles/genes at one locus having opposite effects on reproductive success in males vs females (Different individuals, same locus + same allele; negative correlation of selection coefficient on same allele)

Interlocus sexual conflict

alleles that promote female fitness harm male reproductive success and different alleles that promote male sexual selection harm female fecundity or reproductive success. Different individuals, different loci, different alleles. Counter-adaptation perpetuates sexually antagonistic co-evolution

Sexually antagonistic co-evolution - drosophila

Seminal fluid causes female to produce more eggs, but is also toxic and shortens her lifespan, disincentivizing multiple mating. After 34 generations poly or monogamous, poly females were much more protected against protein and layed more eggs, monogamous lost ability to defend themselves, layed fewer eggs

Arms race between sexes - water striders

Increase in relative armament of females (anti-clasping spines) was associated with decrease in male mating success and decrease in female mating rate

Arms race between sexes - waterfowl

Female anatomy impedes copulation through spirals, dead ends; the weirder the male phallus the more complex the oviduct, typically spiralling in counter directions (successful at impeding copulation) - also an example of chase away selection

Monogamy

1M, 1F

Mating system

How many mates are acquired and what type of pair bond is formed

Polygyny

1M, 2+F

Polyandry

2+ M, 1F

Promiscuity

2+ M, 2+ F - no stable relationship, mating between two individuals only happens once

Assumption of extra-pair copulation

Assumes that the species forms pair bonds

Mating system difference in species reflect differences in? (2)

male and female dispersal patterns and costs and benefits of mate guarding/defense

Mating system - male and female dispersal patterns

Female reproductive success is mainly limited by access to resources, while male reproductive success is limited by access to females (Bateman’s Principle). Thus resources —> females —> males —> mating system

Male and female dispersal patterns - Environmental potential for polygamy (EPP)

Highly clumped resources = highly clumped mates = more polygyny

Widely-distributed resources = widely distributed potential mates = more monogamy

Mating system - specie biology

Species biology dictates the costs and benefits of mate guarding/defence through territory size and receptivity duration

Costs and benefits of mate guarding/defence - territory size

Males that are capable of large territory defence will have more polygyny, those with capacity for only small territory defence can select for monogamy

Costs and benefits of mate guarding/defence - receptivity duration

If synchronous breeding, it doesn’t pay to defend territory and mates, just mate as much as you can on one day

If asynchronous or prolonged, territory and guarding are more beneficial

What is the difference between social and genetic mating systems?

Social is based on observed interactions (e.g. mating, parental care, pair bonds) whereas genetic is based on DNA and parentage

Why does male monogamy exist? 3

Mate assistance, mate guarding and female enforcement

Male monogamy - mate assistance

male gets net benefit from assisting. E.g. many sea birds and birds of prey, emperor penguin

Male monogamy - mate guarding

payoff from guarding is high, few other opportunities exist. Such as when receptive females are super rare. e.g. clown shrimp

Male monogamy - female enforcement

females chase off other females or attack males attempting to mate with other females

Female enforcement - burying beetles

Females interfered with males much more when they were free than when they were tethered, e.g. pulling them back from presenting to other females

Female enforcement - dikdik

Socially and genetically monogamous, even when territory quality improved, but mate guarding and aggression between pairs goes way up during breeding season = herding female back towards territory

3 types of polygyny

Resource defence polygyny, female defence polygyny, lek polygyny

Resource defence polygyny

Males control females indirectly by monopolizing critical resources that females need or that they need to safely lay eggs of care for young

Female defence polygyny

Males control females directly, by defending groups of females either permanently or seasonally, especially when they are social and/or predictable

Lek polygyny

Males aggregate at traditional sites (leks), despite no essentially resources, and display communally. Females free to select a mate and the aggregation of many displaying males at one location greatly facilitates comparison of males by females and the accurate selection of the best one

Three hypotheses for why males aggregate on leks?

Hotspot, hotshot, female preference

Lek polygyny - hotspot hypothesis

males aggregate on ‘hotspots’: males congregate where female encounter rate is particularly high (on female routes) e.g. on the way to food or water

Lek polygyny - hotshot hypothesis

subordinate males cluster around highly attractive males hoping to interact with females attracted to the hotshots… By being near a hot male, you might also get some action

Lek polygyny - female preference hypothesis

females prefer large groups of males where they can mroe quickly compare the quality of males. aggregated males get visited more often by receptive females

Consequences of leks (3)

Opportunity for female mate choice and male-male competition is unusually high

Males tend to be very highly ornamented and perform very striking and conspicuous displays

Females visit several males before copulating and appear to be very selective in their choice

Paradox of the lek

Matings are strongly skedded mostly just a few males, and with strong skew in male reproductive success, a few generations of selection (female choice) should deplete most genetic variation in quality

What maintains genetic variation in lekking species?

Several mechanisms can maintain genetic variation, including balancing selection (overdominance), frequency-dependent selection, and the genic capture hypothesis (condition dependence)

Why do leks form?

form primarily because they allow males to efficiently advertise their presence and compete for mates, potentially increasing their reproductive success

When would a female chose polygyny over monogamy

When territory quality is sufficiently high to support multiple females, as well as in patchy environments (vs homogenous)

Polygyny threshold model - redwing blackbirds

females preferred to mate with already-mated males on better territories over unmated males on poorer land territories (more predation)

Two set ups of polyandry

several males defend one female’s territory together or female defends large multipurpose territory within which several males defend smaller exclusive territories

Polyandry - jacanas

Sex role reversed - resource dispersion influences male distribution which in turn determines female settlement patterns - Females’ territories changed much more (30%) when some males and females were removed vs males only changed like 12%.

Parental care

Any behaviour on the part of the parent that appears likely to increase the survival and fitness of offspring; all through lifespan

Parental effort

expenditure of parental resources (e.g. time and energy) spent on parental care of one or more offspring. varies over lifetime, but must know that time and energy are being spent

Parental investment

Any action on the part of a parent that increase the fitness of its offspring at a cost to any component of the parent’s fitness. Must increase fitness of offspring and must cost parents, so it is hard to prove

Benefits of care - treehoppers/thornbugs

Hatching success depends on the amount of parental care received, due to guarding of eggs by mother

Care can be beneficial if: (3)

Increases offspring survival while associated

Improves offspring quality in a way that increases future survival or reproduction

Directly increase offspring reproductive success when parents and offspring remain associate into adulthood

Costs of care (3)

decreased survival, opportunities to feed, decreased future mating opportunities

Costs of care - decreased survival - lumpsucker fish

Males look after babies; males are much more likely to be caught by otters than females during breeding season, but not the rest of the year; they take much more risks and even will try to fight fish

Costs of care - decreased survival - assassin bug

Males guard; guarding males have lower survival than females and non-guarding males = something is costing them survival

Costs of care - decreased opportunities to feed - mouthbrooding

Mouthbrooding in fish prevents feeding, producing significant decreases in weight in caring parents and reducing brood size (brood weight) of the successive brood

Costs of care - decreased future mating opportunities - rainbow cichlids

Chances of desertion were much higher when F-biased reatio; males abandoned their mate to court extra female, showing that staying with partner to care reduced extra-pair copulation and remating

Pre-fertilization investment (3)

preparation of nests, burrows or territories (may also be mating effort if M-only), nuptial gifts/courtship feeding (if improves RS), egg production

Pre-fertilization investment - egg production - herring gulls

Trade-off between egg volume and post-hatching survival (generally increases with size)

Pre-fertilization investment - egg production - tree frog

Tree frogs produce variable egg size in temporary water bodies compared to permanent water bodies as reassurance, vs permanent fewer larger eggs

Investment between fertilization and hatching (3)

Egg care (inside or outside body), incubation/internal gestation, provisioning before birth

Provisioning before birth - burying beetle

Male and female sense dead body, create chamber where they put carcass and prepare/preserve it, female lay egg around carcass so when young hatch its easier to eat (plus pre-eaten and regurgitated)

Provisioning after birth

young eat food collected by parents or feed on parental secretions (mucus, milkcrop, milk),

Provisioning after birth - poison arrow frog

obligate egg feeder = mother produces unfertilized eggs to feed her tadpoles

Care for nutritionally independent young - buick swan

Cygnets stay near parents for about a year; get better access to feeding areas, even though they can feed themselves