Flashcards in Mate choice Deck (61)
What is mate choice?
A form of intra-sexual selection whereby females preferentially mate with certain males
What is the Sexy Sons hypothesis?
Under Fisherian selection, females select for 'attractive' males as they will sire attractive sons, who will themselves be selected by females and maximise the amount of grandoffspring for the mother.
Are the benefits of the Sexy Sons hypothesis direct or indirect for the female?
Indirect, as her offspring will benefit from the father's good traits
Describe the Sexy Sons hypothesis in terms of alleles p, P, t and T
p = non-choosy females
P = choosy females
t = boring male trait
T = sexy male trait
Can assume P and T become associated, G(PT)
What is the association of alleles called?
Genetic covariance, they vary in response to each other
What happens at low levels of G(PT)?
Female preference and male ornament size are at equilibrium
What happens at intermediate levels of G(PT)?
The costs and benefits of preference cancel out
What happens at high levels of G(PT)?
It becomes unstable and favours 'runaway traits' and extreme preferences
Is there a cost to the female for being choosy?
Only if her preference is extreme, as it restricts her chance of mating. Otherwise it is beneficial.
Does the Sexy Sons hypothesis explain the evolution of mate choice?
No, only how it might be maintained, as the benefit of having sexy sons is relatively small for the female
Is the Sexy Sons hypothesis sensitive to the costs of female choice?
Yes; if she is too choosy then she will not get to mate as extreme ornaments are less likely
Is there much empirical evidence for G(PT)? Give an example.
Yes but very little
Sticklebacks, females preferred red colouration. Intense red or dull males were bred to females of same population. Was found that daughter colour preference for intense red correlated to the intense redness of their brothers, positive correlation.
What is the Good Genes hypothesis?
That ornaments indicate male quality; they are costly to produce and so only the males with the best genes can produce them.
Why does the Good Genes hypothesis convey more benefits to females than the Sexy Sons hypothesis?
Sexy Sons hypothesis ensures production of attractive sons
Good Genes hypothesis ensures production of good quality sons AND daughters
Are the benefits of the Good Genes hypothesis direct or indirect?
Under the Good Genes hypothesis, who described he Handicap Principle? When? What is it?
Male ornaments are seen as handicaps as they are costly to produce and reduce male fitness. Males that invest more into their ornaments are more handicapped but are preferred by females.
What are the parameters P, T and Q in the Good Genes hypothesis?
P = female preference
T = male investment into trait
Q = genetic quality
What are the 2 main problems with the Good Genes hypothesis?
1. The Lek Paradox
What is the lek paradox?
High quality males are consistently chosen by females, meaning the best male will get to mate with all females in a lek. Therefore his good quality alleles will spread to fixation in the offspring and eliminate genetic variation.
If there is no variation in quality, there is nothing for females to choose between and mate choice will not be maintained.
There are three ways to maintain genetic diversity under the Good Genes hypothesis. What are they?
1. Red Queen dynamics
2. Genic capture
3. Mutation bias
How do Red Queen dynamics maintain genetic diversity?
It ensures selection for alleles with different Q values over time.
Who confirmed that Red Queen dynamics are important in host-parasite co-evolution?
Hamilton and Zuk, 1982
What did Hamilton and Zuk (1982) focus on?
North American birds, finding that there was a correlation between blood infection by parasites and fitness-dependent traits like male brightness and song.
Who furthered Hamilton and Zuk's work by studying the sage grouse?
What did Boyce (1990) find in sage grouse?
Lice caused hematomas (swellings of clotted blood) in the air sacs of male sage grouse causing them to discolour. These are used in courtship display and so females can detect lousy males.
Under Red Queen dynamics, male fitness-dependent traits evolve over time in response to parasite infection. True or false?
What is genic capture?
When multiple loci encode a trait (QTL), even small mutations have an effect on phenotype.
What is biased mutation rate?
When mutations are more likely to reduce quality than enhance it.
Who provided two main explanations for the existence of biased mutation rate?
Iwasa et al., 1991