today: monogamy xkcd.com. reproduction reduces survival cb 53.8
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What different reproductive strategies exist, and what are the benefits and risks?TRANSCRIPT
Today: Monogamy
xkcd.com
Reproduction reduces survival
CB53.8
What different reproductive strategies exist, and what are the benefits and risks?
These birds are nesting together, they must be an “item”
10-40% of offspring in “monogamous” bird species are fathered by an extra-pair male
•Social Monogamy = pair lives/works together, but not “faithful”•Sexual Monogamy = pair raise young and only copulate with each other
Mating pairs share genetic information and possibly help in child-rearing
In mammals, child-rearing is most commonly done by the female. She provides milk.
Less than 0.01% of mammals are monogamous
Do Males and Females have different attitudes toward sex and relationships?
On a college campus an attractive male or female asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”Male answers:…Would you go out
with me tonight?= 50% yes
Female answers:…Would you go out
with me tonight?= 50% yes
On a college campus an attractive male or female asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”Male answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?
= 69% yes
Female answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?
= 6% yes
On a college campus an attractive male or female asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”Male answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?= 69% yes…Would you go to bed
with me tonight?= 75% yes
Female answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?= 6% yes…Would you go to bed
with me tonight?= 0% yes
Why do Males and Females have different attitudes toward sex and relationships?
The male perspective on monogamy
Eggs require large resource input.
A clutch of bird eggs can be ~20% of bird’s weight.
Sperm are cheap.
A female kiwi ready to lay an egg.
Eggs require large resource input.
A clutch of bird eggs can be ~20% of bird’s weight.
Sperm are cheap.
Female mammals provide additional resources in form of milk.
Why might females choose to mate with multiple males?
Gunnison’s Prairie DogsSexually monogamous female prairie dogs have a 92% chance of successfully giving birth.
Gunnison’s Prairie DogsSexually monogamous female prairie dogs have a 92% chance of successfully giving birth.
Non-monogamous females have a 100% chance of giving birth
Mating pairs may be genetically incompatibleCystic Fibrosis: F= normal, f= cystic fibrosis
Mom=Ff
Dad=Ff
fF
F
f
FF Ff
ffFfMom=Ff
Dad=FF
fF
F
F
FF Ff
FfFF
Versus
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html
Can females detect compatible genes?
Genetic quality and sexual selection: an integrated framework for good genes and compatible genes.Neff and Pitcher Molecular Ecology (2005) 14 pg19– 38
Benefits for females choosing mates for good genes vs compatible genes
Genetic quality and sexual selection: an integrated framework for good genes and compatible genes.Neff and Pitcher Molecular Ecology (2005) 14 pg19– 38
Benefits for females choosing mates for good genes vs compatible genes
How can a female know which male has successful genes?
Females may choose traits, like large displays, that are disadvantageous for male survival.
How can females determine “good” males?CB 51.30
Color:Bright coloring can be correlated with health…
CB 51.30
But a male with a mate is judged as being high quality even if he is less colorful
CB 51.30
Choosing a mate and reproductive strategies are based on methods to succesfully pass on
genes
VolesPrairie
• Monogamous• Both parents care
for young
Montane• Nonmonogamous• Mother cares for
young briefly
Oxytocin(hormone)
Water/salt balance
Contraction of womb and milk production
Encourages bonding between individuals
Hormones are molecules produced in one cell and signal another.
Oxytocin(hormone)
Water/salt balance
Contraction of womb and milk production
Encourages bonding between individuals
VolesPrairie
• Monogamous• Both parents care
for young
Montane• Nonmonogamous• Mother cares for
young briefly
VolesPrairie
• Monogamous• Both parents care
for young
Montane• Nonmonogamous• Mother cares for
young briefly
Same levels of oxytocin
Hormones are molecules produced in one cell and signal another.
VolesPrairie
• Monogamous• Both parents care
for young
• More receptors
Montane• Nonmonogamous• Mother cares for
young briefly
• Less receptorsSame levels of oxytocin
VolesPrairie
• Monogamous• Both parents care
for young
• More receptors
• ?
Montane• Nonmonogamous• Mother cares for
young briefly
• Less receptors
• ?
Same levels of oxytocin
Inject hormone into brain
VolesPrairie
• Monogamous• Both parents care
for young
• More receptors
• Monogamous
Montane• Nonmonogamous• Mother cares for
young briefly
• Less receptors
• Nonmonogamous
Same levels of oxytocin
Inject hormone into brain
VolesPrairie
• Monogamous• Both parents care
for young
• More oxytocin receptors
• ?
Montane• Nonmonogamous• Mother cares for
young briefly
• Less oxytocin receptors
• ?
Same levels of oxytocin
Block receptors
VolesPrairie
• Monogamous• Both parents care
for young
• More oxytocin receptors
• Nonmonogamous
Montane• Nonmonogamous• Mother cares for
young briefly
• Less oxytocin receptors
• Nonmonogamous
Same levels of oxytocin
Block receptors
VolesPrairie
• Monogamous• Both parents care
for young
• More oxytocin receptors
• Monogamous
Montane• Nonmonogamous• Mother cares for
young briefly
• Less oxytocin receptors
• Monogamous
Same levels of oxytocin
Increase levels of receptors (genetically) in ventral pallidum
VolesPrairie
• Monogamous• Both parents care
for young
• More receptors
Montane• Nonmonogamous• Mother cares for
young briefly
• Less receptorsSame levels of oxytocin
xkcd.com