Lecture 11: maintenance of sexual selection

Question 1

what two types of benefits individuals get from mate choice

Answer 1

• direct benefits
• -material benefits (e.g. food, parental care) that increase the reproductive success of chooser
• indirect (genetic) benefits
• -good genes that will produce high quality offspring for the chooser

Question 2

fertility =

Answer 2

ability to produce offspring

Question 3

fecundity =

Answer 3

potential number of offspring that could be produced

Question 4

direct benefits of mate choice =

Answer 4

• fertile or fecund mate
• good parenting ability
• resources (e.g. food/nest sites)

Question 5

direct benefit of mate choice example:

Answer 5

• Mottled sculpin
• female choice of male parenting ability
• females prefer large males
• large males hatch more eggs

Question 6

indirect benefit mate choice example:

Answer 6

Lekking males provide no direct benefits, females get only genes

Question 7

how is sexual selection for indirect benefits maintained?

Answer 7

• Fisherian Runaway models (a.k.a sexy sons model)
• chase-away models
• good genes model
• compatibilty models

Question 8

Fisherman runaway sexual selection

Answer 8

-females that choose males with attractive traits gain indirect benefits because they’ll produce attractive sons that will in turn be preferred by choosy females

Question 9

fishers runaway model: long tailed mates

Answer 9

• females chooses a long-tailed male
• male offspring have long tail
• females offspring have preference for long tails
• tails keep getting longer until some natural selection cost (e.g. predation) limits the trait

Question 10

under fisherman selection we’d predict that male traits and female preferences should be

Answer 10

genetically linked

Question 11

chase away sexual selection:

Answer 11

exaggerated male traits evolve through antagonistic coevolution between the sexes

Question 12

chase away model example drosophila

Answer 12

1) males seduce females into sub-optimal matings

2) females evolve resistance to such males

Question 13

good genes model:

Answer 13

trait represents quality of male + reflect the viability of offspring

Question 14

compatibility model:

Answer 14

individuals choose partners with complimentary MHC’s to them

Question 15

MHC =

Answer 15

major histocompatibility complex

Question 16

the compatibility model predicts that individuals will prefer partners with __ MHC’s

Answer 16

dissimilar

== result in heterozygous offspring, greater disease resistance