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Terms in this set (180)

Theory for evolution of mate choice when the female receives no direct benefits - specifically, genetic-based female preference for extreme male trait. Driven by female choice for genetically based traits , pushes selection, making males evolve increasingly elaborate traits like bright colors that are impractical for survival. Is an indirect benefit model: females prefer males with extreme expressions of these traits (these traits only benefit the males when they are at their extreme). This indirectly benefits the female or her offspring. At the end, sons will be attractive and have more offspring. Proposed by RA fisher for rapid development of specific physical traits in male animals, eventually leads to male offspring are more likely to possess that physical trait, whereas female offspring are more likely to possess a preference for that trait in males. Over a longer time, the species may be characterized by extreme sexual dimorphism.

There must be a genetic-based male trait beneficial at its extremes. Then, evolution of genetic-based female preference for the extreme male trait occurs. The traits become correlated in offspring, and evolution of the male trait races forward due to correlated selection. Future generations will pass on the alleles for the trait (expressed in males) and the alleles for the trait preference (expressed in females). This can lead to fixation of the trait and preference through positive frequency-dependent selection. The male trait passes the optimal, and only stops when the detrimental value in terms of survival balances the increased mating success. End up with showy traits that initially correlated with fitness but no longer do. They are only maintained because of genetically based female preference in population.
o 2) To enhance quality of offspring
Increase variation in variation
Can get a better mate? increase quality of offspring
If a female has the opportunity to mate with a male of higher genetic quality expect her to mate with him
Conflicts b/w good parent and high fitness highest fitness males aren't always the best parents
Ex: Bluethroat young of the bluethroat have a stronger immune response when they are the result of an EPC than when they are the result of a within-pair copulation
• Always mating with males of better quality
o Certain mates are more compatible with others - genetic compliment - EPC male is more likely to find perfect compliment
o Some pairings just don't work - some sort of biology there
o Females use certain things to pick males - seem to correlate with the mate that is more compatible with her genetically

Mate female with two males in following combos:
-Sibling-Sibling: female has lower proportion of eggs than mating with unrelated individual
-Non-Non: female has more offspring
-Sibling-Non: should be that the proportion falls somewhere in the middle (half are good from non, held are bad from sibling)
-Despite the fact that she is mating with sib and non, fitness still increases suggesting that the better sperm (from non) is beating the sib sperm and fertilizing more eggs
-Non-Sib: changed order to see if whoever mates with female last or first has better chance of fertilizing female, however same results were found and non-sperm competed and were more successful
Parent-offspring conflict. Offspring are trying to acquire resources while the parent is trying to withhold them. The end of weaning occurs when the current offspring and parent are in agreement about the amount of care necessary. For full siblings, this is when the benefit to cost ratio drops below 1/2. Benefit is measured in benefit to current offspring, and cost is measured to reduction in future offspring. In instances where parents produce only half siblings, we should expect the conflict to last longer because the current offspring is less closely related to future offspring. Early on, the benefit to cost ratio is very high, and what the parent is investing in the offspring pays off. Over time, it will drop as the offspring is more able to protect itself and get its own food. Once the benefit to cost ratio drops below 1, resources would be better off given to another offspring. At this point, the parent is giving more to the current offspring than it would take to have another. From the parent's standpoint, it's time to move on, but the offspring still want more. For the offspring to move on, it only makes sense when the parent can care for 2 more offspring just as well
• However, a parent shares only 50% of its genes with the offspring and is equally related to all of its offspring, whereas the offspring is 100% related to itself, but only shares 50% of genes with full siblings (and less with half-siblings)
• As a result, at some point, a parent will probably prefer to reserve investment for future offspring rather than investing in the current one, while the current offspring will disagree.
• As we have seen not all offspring are created equal and even in the absence of parental manipulation of quality we would expect parents to assess offspring quality when deciding how to allocate scarce resources.
• It has been suggested that the gape (inside of mouth) color of baby birds may signal the quality of their immune system and thus offspring quality
• Red gape color is produced by carotenoid pigments in the blood and these are believed to enhance immune function
• Does correlate with fitness but also parents may notice that color more and feed them more and so this is selection on the offspring to get more resources from their parents
o Evidence of both
• In an experiment on barn swallows in which the chicks gapes were colored with food coloring, chicks whose gapes were reddened received more food although chicks whose gapes were yellowed did not receive less food. - both colors being more pronounced but one selected for more.
• Alternative explanations for the role of gape coloration have been put forward, however.

o An obvious alternative is that parents are not assessing offspring quality, but just feeding those chicks whose gapes are more conspicuous under the prevailing lighting conditions.
o Consistent with this idea Great Tit chicks whose mouths were painted yellow received more food than chicks whose mouths were painted red and were less conspicuous in a dark nest box.
o When a plexiglass lid was placed on the nest box however, both sets of chicks were equally well fed.