BIO220H1 Lecture Notes - Lecture 3: Great Reed Warbler, Junglefowl, Barn Swallow
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Intersexual Selection & Mate Choice
• Introduction to the problem
• Examples of female choice in action
• The benefit of female choice (direct and indirect benefits)
• Why do they choose arbitrary traits? Why these traits?
• Any female trait (behaviour, morphology) that biases the mating success of males
toward the “preferred” type (filtering males)
• We will use mating bias, female preference, female choice to mean the
• No implied sense of beauty
As we will see, male choice occurs in some species, and is simply the reverse.
By what mechanisms are females choosing?
• Long‐tailed widowbird
• Satin bower bird
• Barn swallow
• Cichlid fish
• Field cricket
• Jungle fowl
• Field cricket
• Woodhouse’s toad
• Great reed warbler
• Túngara frog
• Sierra dome spider
Sex dimorphism—different elaborations
How to define which trait?
e.g. tail feather
Tail manipulation experiment
• Are long tails preferred by females?
• Manipulate tail length
Experiment (4 treatment groups)
• Natural tail length (N) control
• Reduced tail length (R)
• Elongated tail length (L)
• Sham surgery (S) cut the tail and glue it back→additional control
(BEST) L > N = S > R (WORST)
R, N, S, L have about the same female nests—about the same selection by females
R, N are not significantly different
L has significant increase in female nests
This study also asked:
• Does tail length impact male‐male competition?
• Are long‐tailed males better at holding territory?
The answer was no.
• Tail length seems only to influence female choice
Only affect intersexual selection
Female preference for eyespots in peacock tails
EXPERIMENT 1: Reduction of eye spot number (clipping tail feathers)
EXPERIMENT 2: Alter eye spot colour
Another experiment: Female preference for complex in Túngara Frog
Why doesn’t all males make complex call? Frog-eating bat prefer complex calls too!
→predation against sex selection