Chapter 12: Mating Behaviour Flashcards
sexual selection
a form of natural selection that acts on heritable traits that affect reproduction via mate competition (intra) and mate choice (inter)
mate competition
selection in which one sex competes with other members of the same sex for access to the other sex for reproduction
mate choice
selection by one sex for members of the other sex for reproduction
anisogamy
different sized gametes
isogamy
same sized gametes
how did anisogamy evolve? (assumptions)
- in ancestral marine environment, individuals produce different sized gametes
- each parent has a fixed amount of energy to allocate to gamete production, resulting in a size-number trade off. (as gamete size increases, gamete number decreases, and vice versa)
- zygote viability is related to its size. larger zygotes have higher viability because they contain more nutrients
Bateman’s Hypothesis
there is a greater variance in reproductive success among males than females.
some males will have more offspring, some will have none, which leads to skewed distribution of reproductive success within the species.
Males reproductive success increases as they mate more, but females have a cap- they can only produce so many offspring in one season.
in species where males compete for access to females, the variance in male reproductive success is higher because the number of mates a male can obtain is limited
females, who invest more in reproduction, have more limited reproductive potential and have lower variance. Her restraint is physiological.
parental investment theory
Proposed by Trivers
the sex that pays the higher cost of parental investment should be choosier when selecting mates. the other sex will experience intense sexual selection
red deer research question
are antlers weapons used in mate competition?
red deer methods
collect and weight antlers when shed
use blood samples to determine reproductive success (paternity testing)
red deer results
average antler mass over an individual’s lifetime was positively correlated with his total lifetime breeding success. bigger antlers = more success
dung beetle research question
what is the role of male’s horn-like projection?
dung beetle hypothesis
large horns provide an advantage in mate competition
dung beetle prediction
males with the larger horns will win the most fights
dung beetles methods
stage fights between males matched for body size, but not horn length
record outcome of interactions and mating success
dung beetles results
males with smaller horns tended to lose, males with largest horns tended to win
peacock research question
are peacock tails an ornament used in mate choice?
peacock methods
measured tail length and male body size, number and duration of tail displays, number of vocalization and copulations
peacock results
longer body sizes and tail = more likely to acquire display site
more eyespots = more copulations
what are peacock ocelli?
the eye spots on their tails
guppies sensory bias research question
how does a male trait become selected in female mate preference?
guppies sensory bias hypothesis
sensory bias hypothesis: female mating preferences are a byproduct of pre-existing biases in a female’s sensory system
guppies sensory bias prediction
males and females should be attracted to orange coloured objects because orange is associated with carotenoids
guppies sensory bias methods
several populations, place small colour discs on leaf in water
record all approaches and pecks
guppies sensory bias results
high preference seen in both males and females, but a bit more in females. lots of pecks at orange disc.
direct material benefits in mate selection and an example
material resources obtained by a female from mating with a particular male.
ex. nuptial gift: a physical resource like a food item that a male provides a female to enhance his chances of mating
indirect material benefits female mate choice
genetic benefits females can obtain for their offspring by mating with males that have high genetic quality
fireflies mate choice research question
how does the variation in the duration of male flashes affect female mate choice and fitness?
spermatophore
a structure or package containing sperm which is transferred from a male to a female during reproduction.
the specific structure and function may vary but the purpose is to deliver sperm to the female’s reproductive organs. It may contain sperm and also nutritional substances and protection for sperm.
spermatophores can be a part of the male’s reproductive strategy.
spermatophore transfer mechanisms
there are often specialized reproductive organs or structures for spermatophore transfer.
direct insertion: male directly inserts spermatophore into female’s reproductive organs (insect common)
capsule placement: spermatophore is placed in a location where the female can access it. The female may then take the spermatophore on her own. (Arachnid common)
transfer via structure: some species like octopi have specialized structures like hectocotylus to place it in the female
sperm web/packet: (spider common) sperm web or packet is structure containing spermatophore. left for female to retrieve.
fireflies mate choice methods
measured male flash duration and spermatophore size
created flashes of different lengths and measured female response
fireflies mate choice results
males with longer flashes had bigger spermatophores.
females responded more to longer flash durations.
lizard mate choice research question
how does territory quality affect female choice and fitness?
territory quality is based on rockiness
lizard mate choice methods
larger males have territories with more rocks
added rocks to small male territories, removed rocks from large male territories
observe female mate choice
measure egg laying date and egg mass
lizard mate choice results
females preferred improved territories
on improved territories females laid eggs sooner and produced larger egg masses
females select males based on territory quality and there seems to be a fitness gain by doing so
indirect genetic benefits
genetic benefits females can obtain for their offspring by mating with males of high genetic quality
females may select males based on
secondary sex characteristics
runaway process
an evolutionary process in which a male trait coevolves with female preference and it becomes increasingly exaggerated
handicap principle
well developed secondary sexual characteristics are costly to survival but reliable signals of fitness
good genes
alleles of high quality individuals
mate choice in frogs methods
captured, ID’d males from 4 ponds
observed # of matings
collected egg masses and reared in lab, measured tadpole growth rate and survival and genotyped them
mate choice frogs results
males with more offspring had tadpoles with highest growth rates
females were selecting for genetic benefits
bird parasitism research question
how does parasite load affect mate choice?
Hamilton-Zuk hypothesis
females prefer males with greatest expression of secondary sex characteristics
bird parasitism hypothesis
hamilton-zuk, females will prefer males with most expression of secondary sex characteristics because these males have highest immunocompetence if male immunity is a heritable trait.
bird parasitism predictions
females should prefer to mate with males that have greatest expression of secondary sex characteristics
high parasite loads will reduce expression in males
bird parasitism methods
infect half of the males with intestinal nematode
measure size and colour of comb
conduct mate choice test with control and infected males
bird parasitism results
control males had larger combs
females preferred control males
mate choice spiders research question
what is the importance of pheromones as signals of male quality in mate choice?
how do male spiders use pheromones?
they expel a sticky substance to aid in prey capture, which also includes pheromones for females. the males dont provide anything, so females choose for indirect benefits.
spider mate choice methods
experiment in Y test chamber.
Phase 1: males at ends of arms, foam on floor to prevent tactile signals. chemical cues only
Phase 2: pheromones of males on filter paper at ends of arms
mating experiment: half females mated with preferred male, other half with non preferred male
spider mate choice results
chose same male from phase 1 to phase 2.
females with males they preferred had larger eggs and a higher hatch rate
why does mate choice matter in captive breeding?
captive breeding programs need to take into account genetic diversity and mate choice, since mate choice ensures more viable offspring, which is important since many of these programs are meant to increase population size
mate guarding
a male follows his mate to prevent her from mating with rivals
extra pair young
offspring of a pair bonded female produced outside the pair bond by a third party male
warbler research question
how effective is mate guarding?
warbler mate guarding results
males with fewer extra pair young spent lots of time with the female.
males who were experimentally removed had more extra pair young than controls who were present.
warbler conclusion
mate guarding can be an effective strategy for increased paternity assurance
sperm competition
competition between sperm of different males to fertilize eggs
cryptic female choice
when female influences the fertilization success of sperm from one male over others
inbreeding depression
a reduction in fitness as a result of mating with close relatives
methods of sexual selection after mating
sperm competition
cryptic female choice
inbreeding depression
mate guarding
extra pair young
tree swallow results
increased copulation rate resulted in decreased extra pair offspring
tree swallow conclusion
males can reduce paternity loss from sperm competition by increasing copulation frequency
alternative mating tactics
multiple behavioural mating phenotypes in a population
satellite male
alternative, parasitic mating tactic in which a male remains near parental male to intercept females that are attracted to him
sneaker male
alternative, parasitic mating tactic in which a male attempts to avoid detection so that he can quickly enter a parental territory to fertilize eggs being deposited in a nest
conditional strategy
the flexibility with which one chooses a particular strategy based on an individual’s condition
ESS
a strategy that, if adopted by individuals in a population, cannot be trumped by another strategy because it yields the highest fitness
satelitte tree frogs observations
males can be dominant or satellite
dominants call to attract females
satelitte lives near dominant, stays quiet to intercept females attracted to caller.
some males exhibit both strats.
tree frogs methods
record calls of dominant and satellite males
synthesize calls
conduct choice tests for females and satellite males
tree frogs results
dominant males were larger and older
dominant males had lower frequency calls
males adopt conditional strategy if dominant males are removed
females and satellites prefer low frequency calls
sunfish research question
what is the reproductive success of parental and sneaker male sunfish?
sunfish methods
map nest locations
capture parental males, females, sneaker males and eggs
genotype analysis
sunfish results
parentals are older and bigger
sneakers dont sire much young
mate choice copying research question
do females copy the mate choice of other females?
mate choice copying methods
focal female in a mate choice test with males matched for size and colouration
model female placed next to non chosen male with focal female observing
focal female given mate choice test
mate choice copying results
most females spent more time with male that had been near model female
females switched their mate choice preference to copy the model female
