lecture 17 Flashcards
Material benefits: moth example
Example of nuptial gifts; males consume toxins while they are larvae and these alkaloids can be passed to female during mating; these can help protect the eggs and increase offspring survival, and can also increase survival of the female since spiders won’t eat you with that scent/taste
Nuptial Gifts- Hangingflies
males give female prey item to chew on during mating; up to a certain size-the larger the prey item, the longer duration of copulation, so beneficial to have larger item
Redback spiders & Sexual Cannibolism
Much smaller male ejaculates into female’s web, scoops it up and inserts into female; then male offers himself up, letting female eat him; benefits: eaten males have larger chance of fertilizing eggs, female is less likely to mate soon after she eats, male has high risk of predation if survives; experiment shows female is likely to eat males when she is unfed/hungry and will let males go if she already ate
Material benefits-Territory
Carving bees
females carve off cotton to build a nest with, which is located in the territories of males, so females will seek territories with good resources; males that own territories with good resources will have better mating success
Material benefits-Sufficient sperm, ex. Fruit Flies
when female is given chance between virgin male and one that has already mated, almost always will choose virgin because has more sperm to offer; as part of transfer of sperm, males also transfer things that lower the lifespan of females, so in best interest to get as much sperm as you can so don’t mate multiple times
Material benefits-Parental ability, ex. blackbirds
mates that are able to defend high quality areas are preferred by females, because these birds are able to successfully forage and bring back food, good quality to have as a future “father” to offspring; important for male to demonstrate good hunting/nest gathering abilities
Mate choice criteria: Quality
choose male based on quality rather than material benefit, because females are limited by good genes; females assess phenotype of males to determine if good genotype; lower quality males may cheat to make it seem like they are high quality
Quality example in birds
Physical well-being
presence of bright colors on males signifies good nutrition and foraging abilities because need proper diet to get colors and also signifies low parasites load, since birds with lots of parasites are unable to get those colors
Quality example in fiddler crabs-level of dominance
males show dominance by the size of their large claw and use it to impress females; also create pillar structures at their nest, which are used to attract females
Quality: Longevity, example in Warblers
number of songs warblers can sing increases with age; those with largest song repertoire are chosen as mates, because shows that they have good genes to live a long life; song repertoire size positively correlates with offspring survival
Spider experiment: effects of female mating history on male and female offspring condition
there was a low food and high food condition, and looked at offspring health after double mating or single mating and rejection of second mate; male offspring were not affected by multiple mating or food availability; female offspring of double-mated females had better body condition compared with single-mated females only under low food conditions
Runaway sexual selection
preferred trait is initially advantageous, but then becomes more and more exaggerated until survival cost becomes too great to maintain it; genes for female preference and for preferred trait become linked and both increase in frequency; ex. peacock’s tail, which attracts females, but greatly impairs mobility
Fisher’s runaway model, using peacock tail as trait
Tail length initially increased due to survival advantage and then gene for female preference arises which makes length continue to increase due to female choice; eventually it surpassed optimal tail length for survival, but continued to increase because sexual selection value is so great, even at the expense of fitness due to survival
trait and preference in three spine sticklebacks
son’s intensity of red coloration is correlated with daughter’s preference for red; evidence for genetic correlation between trait and preference
Stalk eyed flies
heritable variation in distance between eyes in males and female preference for stalk length; experiment shows linkage between eyestalk length and preference- if offspring receive genes for long eyestalks, receive gene for preference for long eyestalks; genetic correlation between sons and daughters within families: length of son’s eyestalks correlates with daughter’s preference for that certain length; also correlation between length of father’s eyestalks and daughter’s preference; males with longest eye stalks are most resistant to parasites and most likely to give reasonable sex ratio to offspring (case for better genes)
