Sexual selection 2- Week 3, part 4- Choice for indirect benefits (Chase-away and good genes). Flashcards
Runaway selection working- Evidence for co-evolution:
What works?
Where does the best evidence for this come from?
Explain the example.
Runaway selection
Studies- animals in wild- e.g. sticklebacks.
Males- have bright red bellies- females pay attention- prefer the reddest bellies.
Continuation from runaway selection working- Evidence for co-evolution:
When studying sticklebacks, what did they find?
Essentially, what was there a correlation between?
What took place?
Next generation- positive correlation- between intensity of red colouration + strength daughters preference for colour red.
Male trait and female preference for the trait.
Coevolution- between trait and preference.
Assortative mating + genetic correlation between trait and preference:
What happens if a male with long eye stalks mates with a female who has a preference for long eye stalks?
What will their sons be?
What will their daughters have?
Can this happen for a male with short eye stalks and a female with a preference for short eye stalks?
Essentially, what do we see here?
Offspring will have a gene for long eye stalks + preference for long eye stalks.
Sexy sons.
Good taste.
Yes.
How trait + preference get passed onto the next generation together.
Experimental evidence for runaway selection working:
What is one condition in this study?
What is another condition in this study?
What was the last condition?
How many generations did they do this for in both groups?
Did they stop others, apart from those two groups, from breeding?
Those with longest eye stalks were bred together
Those with the shortest eye stalks were bred together.
Control group- let them breed randomly.
13 generations.
Yes.
Continuation from experimental evidence for runaway selection working:
What happened after 13 generations?
What is all of this called?
Group 1 = males with longer eye stalks.
Group 2 = males evolved to have shorter eye stalks.
Selective breeding.
Continuation from experimental evidence for runaway selection working:
What was interesting about this research?
What happened to females who came from the population where males were being selected for long eye stalks?
What happened to the females who came from the population where males were being selected for short eye stalks?
Females also changed- even though they were not selected for anything like preference.
Had a strong preference for long eye stalks.
Has a preference for short eye stalks.
Continuation from experimental evidence for runaway selection working:
What did the authors conclude?
Were the genes for long eye stalks linked to genes that coded for female preference for eye stalks?
Essentially, what happened?
Female preference changed because of selection.
Yes.
Selecting long eye stalk male = selecting females who liked it.
Chase-away selection:
What is chase-away selection?
Can it be considered the opposite of run away sexual selection?
What do males have?
When do females still prefer males?
What can this be for females?
Another mechanism- leads to evolution of exaggerated traits- in an arbitrary way.
Yes.
Mutation- exploits pre-existing sensory bias in females.
Still preferred despite not providing no material or genetic benefits.
Costly.
Continuation from chase-away selection:
What does this create in females?
What does this then lead to?
What happens each time?
READ THE EXAMPLE ON SLIDE 8 BY THE UNIVERSITY OF ARIZONA.
Selection pressure- to resist attraction of the trait.
Selection pressure in males to exaggerate the trait.
Males become better at exploiting females sensory bias + exaggeration of traits in males.
Continuation from chase-away selection:
However, what is a bad thing and why?
What can it even be?
Extravagant displays- costly to produce + maintain.
Dangerous.
What do chase away + runaway mechanisms only really improve?
Competitive ability and attractiveness.
Good genes:
For good genes sexual selection, what are traits?
What do traits signal?
Why is it in quotation marks?
What kind of benefits?
Indicators.
Heritable qualities- improve fitness- like competitive ability- I.e. “good genes”.
Do not know if genes are good.
Indirect benefits.
Continuation with good genes:
What does good genes sexual selection involve?
Female- choose males due to whether or not they possess heritable qualities that improve offspring fitness (indirect benefits).
Good genes (why?):
In many species, what do males only provide females with?
Who is this particularly in?
So what should females pick?
Are the best gametes a set of genes that will best contribute to the fitness of her genes when united with them?
What varies from females to females?
Gametes (sperm).
Mammals.
The best gametes (ones that produce high quality offspring).
Yes.
What counts as good genes.
Continuation from good genes (why?):
What does female choice lead to?
Who did an experiment on fruit flies and when?
What happened in the experiment?
What does evidence from studies on fruit flies suggest?
Increased reproductive success.
Linda Partridge (1980).
One group- chose which male to mate with.
Another group- no choice, random.
Females- selectively choose mate- that best contributes to offsprings fitness.
