Sexual selection 2- Week 3, part 1- Introduction to mate choice. Flashcards
What is sexual selection?
What type of selection will we be speaking about today?
Selection that operates via competition for reproductive opportunities rather than competition for survival (natural selection).
Intersexual selection.
What is intersexual selection?
Who usually does the choosing?
Are there exceptions for males?
Is this essentially mate choice?
What is intrasexual selection not always?
Members of one sex choosing which members of the other sex to mate with.
Females.
Yes.
Yes.
Male competing with other males.
Bateman’s (1984) classic study of fruit flies:
Why do females do the choosing?
What did Bateman’s study show?
Due to differences between males and females- they benefit in a different way.
Males- can increase offspring they leave behind- by mating with multiple females.
Continuation from Bateman’s (1984) classic study of fruit flies:
What does female mating success not depend on?
What happens for females?
What do you end up with?
Number of mates she mates with.
The eggs they lay will get fertilised regardless of whether they mate with 1, 2 or more males.
You will end up with effective polygyny.
Effective polygyny:
What happens in terms of males?
Do the males assume that they will be one of the males who get to mate with a lot of females?
Some get to mate with lots of females, some mate with none.
Yes.
Continuation with effective polygyny:
As some males do not get to mate with any females, what does this lead to?
What does this then lead to?
More variance than females in their reproductive success.
Males competing for access to females.
Can females benefit from promiscuity?
Yes- but not as much as males.
General pattern across species:
How can females increase their reproductive success?
How can males increase their reproductive success?
By investing more in eggs or offspring (parental effort).
By fertilising more females (mating effort).
Continuation from general pattern across species:
What did Trivers (1972) say?
But what can happen?
Females are a limiting resource over which males compete.
Only some males can capitalize on multiple matings.
Mate choice:
Who do choosy females do?
What do indiscriminate males do?
What are these both?
What does that mean?
What are there however (for the previous question)?
Select the best males.
Compete for females.
Caricature.
Has some basis in reality- captures what we see in a number of species like mammals and birds.
Exceptions.
Continuation with mate choice:
What is mate choice?
What is mate choice not?
Pattern of behaviour- shown by members of one sex- that leads them to mate with the members of the other sex more than others.
Conscious and deliberate.
Continuation with mate choice:
When does mate choice occur?
READ slide 11 example with marmots (+ slide 10).
Occurs when effects of traits in one sex leads to non-random matings with specific individuals of the opposite sex.
Done it?
Rejection:
What can also be a form of choice?
Give an example of an animal which can reject.
Rejection- choosing which male not to mate with.
Female cane toad- if she does not want to mate with a male who tried to mount her, she can inflate her abdomen which will push him away.
Who else can be choosy?
Give an example with an animal.
Give an another animal which can be choosy.
What is all of this called
Males.
Crabs- some species- males prefer larger crabs- can lay more eggs.
Seahorses- males do parental care- prefer larger females- better nourished + more eggs.
Sex role reversal.
Reversed sex roles:
What is classed as reversed sex roles?
Where is this common in?
Can males also be choosy in species where they do not make a contribution to offspring care?
Male mate choice and female-female competition.
Species- males do parental care- females compete.
Yes- in Topi.
Continuation from reversed sex roles:
What happens in Topi?
What happens when they are short on sperm supply?
What can females gain from being choosy?
Successful males- mate with many females- sperm runs out (sperm depleted).
Be choosy- fight off undesirable females.
Direct and indirect benefits.
Mate complementarity:
What is mate complementarity?
What can males do?
Needing to mate with a mate that has the same characteristics as you.
Be indiscriminate + make mistakes.
Continuation from mate complementarity:
Give an example of an insect which does this.
Explain what they do.
What is this an example of?
Male jewel beetle.
Mistake females for beer cans- mate with it- beer cans look similar to females; are orange, dimpled and big.
Rule of thumb- making decisions with it.
Benefits of being choosy:
What are the benefits you can get from being choosy?
What is a direct benefit?
What are indirect benefits?
Give an example of an indirect benefit.
Direct and indirect benefits.
Non-genetic- improves reproductive success + offspring survival.
Genetic benefits- heritable qualities- improve offspring fitness.
Competitive ability.
Continuation from the benefits of being choosy:
Give an example of a direct benefit and what this can lead to.
What else can you say about direct benefits?
Food- female will lay more eggs.
Are immediate.
Direct benefits:
What things can be considered a direct benefit?
3 things.
- Things which make her produce more eggs like food.
- Things which make her produce more offspring.
- Things which increase the offspring’s survival- like the male feeding them would be a direct benefit.
What makes it a direct benefit essentially?
Not related to genetic quality of young = direct benefit.
Choice for direct benefits:
What are three direct benefits?
Explain them.
1) Mate complementarity: will produce young.
2) Mate fecundity/fertility: female lay lots of eggs- need males who produce lots of sperm- to fertilise it.
3) Immediate gains- nuptail gifts.
Continuation with choice for direct benefits:
What is another three direct benefits.
4) Parasite avoidance- avoiding males with parasites to keep your health and that of your offspring good.
5) Parental care- males caring for young.
6) Protection.
