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Slide1
Chapter 7: Sexual Selection
Intersexual and Intrasexual SelectionEvolutionary Models of Mate ChoiceLearning and Mate ChoiceCultural Transmission and Mate ChoiceMale-Male Competition and Mate ChoiceSlide2
I
n 1860, Charles Darwin wrote in a letter to his friend Asa Gray that “…the sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!” Darwin was worried that the peacock’s tail couldn’t possibly help in its survival, and thus could be construed as evidence against his grand theory of evolution by natural selection.Slide3
Intersexual and
Intrasexual SelectionSlide4
Bateman’s Principle
Females are choosier because eggs are expensive to produce, thus female RS (reproductive success) is limited compared to males.
Female choosiness in mate selection should create greater variance in male RSSlide5
The direct benefits model of female mate choice.
Here males provide a direct benefit (in this case, food), and females choose males based on how the resource affects their fitness. Prey items are shown in green. (Based on Kirkpatrick and Ryan, 1991) Scorpionfly nuptial gifts.
Evolutionary Models of Mate
Choice:
Direct benefits and mate choiceSlide6
Scorpionflies
and nuptial gifts. To obtain mates, male scorpionflies present females with nuptial gifts, which are prey items that the females consume during courtship or mating. The male (top) provided the female (bottom) with a blowfly (at arrow), which she eats as they copulate. (Thornhill, 1980)
Evolutionary Models of Mate
Choice:
Direct benefits and mate choiceSlide7
Evolutionary Models of Mate
Choice:Direct benefits and mate choiceSlide8
Evolutionary Models of Mate
Choice:Good genes and mate choiceIndirect benefits in pronghorns. Offspring males that had large harems (green line) had higher survival rates than offspring from other males (orange line), suggesting that females were selecting males based on some measure of a male’s genetic quality.
(Byers
and Waits,
2006)Slide9
Evolutionary Models of Mate
Choice:Parasite resistance and good genesHamilton and Zuk hypothesis (1982) Handicap Principle (
Zahavi
, 1997) and “proxy cues” (
Milinski
and Bakker, 1990)Slide10
Color, parasites, and good genes.
One reason stickleback females may prefer the most colorful (red) males is that color indicates resistance to parasites.Evolutionary Models of Mate Choice:
Parasite resistance and good genesSlide11
Female sticklebacks prefer males with more
Major Histocompatibility Complex (MHC) alleles. Female sticklebacks spent more time on the side of the tank with males that had many different MHC alleles. (
Reusch
et al.,
2001)
Evolutionary Models of Mate
Choice:
MHC and good genesSlide12
Evolutionary Models of Mate
Choice:MHC and good genesSlide13
Evolutionary Models of Mate
Choice:Runaway sexual selectionSlide14
Evolutionary Models of Mate
Choice:Sensory bias and the emergence of mate choiceSlide15
Evolutionary Models of Mate
Choice:Sensory bias and the emergence of mate choiceSlide16
Learning and Mate ChoiceSlide17
Learning and Mate Choice:
Sexual imprintingSlide18
Cultural Transmission and Mate Choice:
Mate-choice copyingBlack grouse and mate-choice copying. Males try to attract females with which to mate by displaying on leks
. This involves strutting, flapping their wings, jumping in the air, and hissing while females
observe (
G
ibson, 1991). Slide19
Male-Male Competition and Sexual Selection:
Red DeerSlide20
Male-Male Competition and Sexual Selection:
Elephant sealsSlide21
Male-Male Competition and Sexual Selection:
Pinnipeds: a phylogenetic perspectiveHarem size and sexual selection. In pinnipeds, there is a positive relationship between harem size and the relative difference in size between males and females. Each point represents a comparison between two species of pinnipeds (
Lindenfors
et al.,
2002).Slide22
Male-Male Competition and Sexual Selection:
Male-male competition by cuckoldrySlide23
Bluegill morphs.
(A) Bluegill parental male preparing a nest. (B) Sneaker males hiding behind plants awaiting a chance to quickly sweep into a parental nest. (C) A satellite male swimming over a nest containing a male and female. (
D
) A satellite male swimming between a parental male and a female. (
E
) A composite of A–D. (Based on Gross, 1982)
Male-Male Competition and Sexual Selection:
Male-male competition by cuckoldrySlide24
Male-Male Competition and Sexual Selection:
Male-male competition by cuckoldryhttps://www.youtube.com/watch?v=4FmMZen3sKI