chp 8: mating system Flashcards
the term mating system is used to describe
the ways in which animal societies are structured in relation to sexual behavior
the mating system specifies
whom males mate with and under what circumstances
who dictates the mating system
politics, religions, and the culture
mating behavior and mate choice play a major role in determining
reproductive success
mating behavior includes
seeking or attracting mates, choosing among potential mates, competing for mates, and caring for offspring
what does promiscuous mating mean
mating with no strong pair-bonds or lasting relationships
what does monogamous mating mean
one male mates with one female
males and females with monogamous mating systems have similar
external morphologies
polyandry
for male: share one female
for female: sole access to several males
monogamy
for male: sole access to one female
for female: sole access to one male
polygyandry
for male: share several females
for female: share several males
polygyny
for male: sole access to several females
for female: share one male
mating systems are important to understand because
they reflect the result of natural selection on
1) mate choice
2) strategies for maximizing individual reproductive success
monogamous mating systems
1) one male, one female for life span of the individual (very rare)
2) one male, one female per breeding season
serial monogamy
one male, one female per breeding season
which monogamy system is most common
serial monogamy
monogamous mating in animal was designed for
one mating season
monogamous mating in animal is relatively rare in
large, conspicuous, daytime species
monogamous mating in animals is common in
smaller diurnal species
example of smaller diurnal species with monogamous mating
old-field mouse
in lifetime monogamy, what percent of the offspring in a family group were fathered by the male in their burrow
90%
polygamous mating system include
polygyny and polyandry
advantage of polygamous mating system
it increases the variance in reproductive success in the sex that has more than one mate per season
disadvantage of polygamous mating system
reproductive success is not equally distributed within male species and between both species
species with polygamous mating systems are usually
sexually dimorphic
sexually dimorphic
males and females have different external morphologies
in polygyny the males are
usually showier and larger than the females (for protection)
in polyandry the females are
more showy than the males
what is an important factor that constrains evolution of mating systems
needs of the young
an example where a male maximizes his reproductive success by staying with his mate and caring for his chicks (monogamy)
bird species where chicks need a continuous supply of food
an example where a male maximizes his reproductive success by seeking additional mates (polgyny)
bird species where chicks are soon able to feed and care for themselves
what influences parental care and mating behavior
certainty of paternity
what is certainty of paternity
females can be certain that eggs laid or young born contain her genes
what does paternal certainty depend on
mating behavior
in species with internal fertilization, paternal certainty is
relatively low (because mating and birth are separated over time)
males are monogamous when
there is a significant fitness advantage/benefit or when resources are relatively scarce
advantage of monogamy for males
male fitness may be highest when they are providing male assistance/care
certainty of paternity is what when egg laying and mating occur together (external fertilization
much higher
what is the proximate cause behind monogamy
accumulation of neurochemical (dopamine) in the brain area (nucleus accumbens (rostal shell)) and the binfing of the D1 (agression) or D2 (friendly) to Dopamine causes different behaviors
how does one male control many females
1) may hold critical resources (resource defense)
2) females may aggregate making them easily defensible (female defense)
3) female may pick male from group of males based on display (male dominance)
example of female defense polygyny
australian wasp (epsilon)
characteristics associated with female defense polygyny
1) males mature earlier than females (and start looking for where mates will emerge)
2) females have low productivity (so they can receive sperm) and live short lives
3) females mate shortly after becoming adult
4) females grouped close together in space
is polyandry common
no it is not that common
what are the theories of the conditions that led to polyandry
1) limited resources (so females desert their young and look for more mates)
2) abundant resources and mate availability
3) availability of additional males led to female desertion
two forms of polyandry
cooperative polyandry and resource defense polyandry
cooperative polyandry
many males defend a female’s territory
1) all males mate an equal number of times with the female
what jobs do males help with in cooperative polyandry
aid in incubating the eggs, help defend the group’s territory, feed the female and chicks
resource defense polyandry
females defend resources that are needed by males
what distinguishes cooperative polyandry from normal polyandry
cooperative form is more egalitarian (equality)
in normal polyandry there can be an alpha male the mates more often with female than a beta male
the forms of polyandry have two different types
simultaneous or sequential
simultaneous polyandry
females mate with two or more males at the same time
sequential polyandry
female mates with one male, and then leaves him to mate with another
older females are more likely to be
simultaneously polyandrous, indicating that might be a more successful strategy
benefits of polyandrous mating
1) sperm replenishment
2) material benefits
3) genetic benefits
4) convenience
disadvantage of polyandry
greater within-group conflict, lack of genetic interest, more competition for greater representation in the next generation
what determines the form of polygamy
incentive, parental care costs, opportunity, sex ratio
incentive
the type of polygamy will depend on who (which parent) has the greatest incentive to desert the young
(benefits males more to desert which is why polygyny is more common)
parental care costs
these costs include: simple energetic needs, the risk of survival, or even the cost of losing future reproductive opportunities
how is parental cost measured
in terms of the number of offspring an individual gets into the next generation if they stay vs. the number they would produce if they desert
opportunity
males have better chance to desert because eggs must be laid one at a time and it can take several days for a clutch to be laid
sex ratio
in general if you are a member of the limiting (rarer) sex, then it makes more sense to desert. if you are the common sex you will invest in offspring that you already have
another name for polygyny and polyandry occuring in the same population
promiscuous
what are the health risks for a female in a promiscuous mating system
sperm are vectors of diseases and disease-causing agents from male and female genitalia hitch a ride on sperm tails and work their way to the uterus
how is disease from sperm taken care of
menstruation
menstruation hypothesis was developed by who
margie profet
menstruation hypothesis
menstruation is a defense that has evolved in females to rid the female reproductive tract of pathogens carried in by sperm
where should menstruation be common
in breeding systems where females engage in sexual activity with many partners
factor that influence animals into polygyny
if resources are sufficiently abundant, patchy, or both
depending on the resource distribution it may pay an individual to choose to mate with
an already mated bird with a great territory than to choose monogamy with a bird in a poor territory
if females track resources and males track females, them the mating system in a population is tied to
the distribution of resources
females track
resources
males track
females
under which condition will a mating system move from monogamy to polygamy
polygyny threshold model
a female’s decision to occupy a certain territory depends on
the territory quality NOT number of females present
surreptitious promiscuity
mating beyond the pair (extra pair copulation)
the occurrence of extra pair copulations has
led ethnologist to consider the difference between social and genetic monogamy
social pair bonding
individuals establish a pair bond with one partner but mate with multiple partners during the breeding season (open relationship)
how do we know which offspring came from EPC
genetic analyses such as DNA fingerprinting techniques
sperm competition
in some promiscuous mating systems, males compete not only for access to mates but directly for eggs
competition can also occur after
a female has mated with several males
what leads to competition over access to fertilize eggs
females storing sperm from numerous mating
how does sperm compete
sperm size, testes size, sperm shape, time of copulation, sperm velocity
in cases where sperm competes, selection can operate how on carious attributes associated with sperm competition
directly
cryptic mate choice
a procedure wherein females mate with many males but decide specifically which male’s sperm will be the one to fertilize their eggs (hide choice from males)
how does cryptic mate choice affect mate preference in females
this procedure permits females more control over mate preference
