Transcript Sexual Selection

Sexual Selection
I.
Motivation
Sexual Dimorphism is
Frequent
Figure 11-1
Figure 11-3
The sexual dimorphism in
Scarlet Tanagers, male, female
Wesern Tanagers, male female
long-tailed widowbirds
Human males and females differ in height
Why this sexual dimorphism
Selection on survivorship and reproduction
Ability to obtain mates:
Sexual Selection:
Different reproductive success due to variation
among individuals in success at getting
mates
If there is heritable variation in a trait that
affects to ability to obtain mates, then variants
with higher success at obtaining mates will
become more common over time
II. Limits to reproduction differ between the sexes
Guess What?
With few exceptions, females invest much
more time and energy in the production
of young
Figure 11-6
Asymmetries in sexual reproduction in rough-skinned newts
Asymmetries in sexual reproduction in rough-skinned newts
males
females
Exception to the Rule?”
Asymmetries in sexual reproduction in broad-nosed pipefish
Male with
Kids (in pouch)
Males
Females
Consequences of Asymmetric
Limits on Fitness
• Members of the sex subject to strong sexual
selection will be competitive (Male-male
competition)
• Members of the sex subject to weak sexual
selection will be choosy (Female Choice)
• Bateman’s rule, males limited by access to
mates, females limited by resources
III. Natural Selection Limits Sexual Selection
e.g., marine iguanas
Larger iguanas expend more energy on metabolism
Male marine iguanas in combat
Large territorial males
Alternative mating strategies in coho salmon
IV. Male Access to
Females
Sperm Competition
Sperm competition in damselflies
Sperm Swimming Speeds
Sperm morphology
in rodents
All for one and
one for All!
Infanticide
V. Evidence for Sexual Selection on Trait: Female Choice
Long tail feathers are a ball-and-chain for male red-collared widowbirds
Female red-collared widowbirds prefer long-tailed males
VI.
Fisher’s
Run Away Sexual Selection
An example from UMD
How runaway selection works in theory
VII. Good genes model of sexual selection
Are male gray tree frogs that give long calls genetically
superior to males that give short calls??
Courtship and mating in hangingflies
VIII. Origin of Trait Selection
Water mite waiting in ambush for a copepod, male has found her
A phylogeny of the water mite Neumania papillator and several
related species.
The boxes above the tips of the branches indicate which species
have net-stance and which species have male courtship
trembling. A colored box indicates the trait is present; an open
box indicates the trait is absent. The two versions of the
phylogeny show the two most likely scenarios for the evolution
of these two traits. Redrawn from Proctor (1992).
Lilies from from SW Aust.
IX. Sexual Selection in Plants
X.
SEXUAL
SELECTION
IN HUMANS
Kipsigis men and women
A. Preindustrial Finnish Population
B. Pimbwe, a horitcultural society in Tanzania
unokais (killers) versus non-unokais among Yanomamö men
Figure 11-50
Human Stature
Taller Polish Men Have More Children:
Importance of physical attractiveness in mate choice versus
parasite prevalence in 29 human cultures
GENETIC DIVERSITY REVEALED IN HUMAN FACES
Hanne C. Lie, Gillian Rhodes, and Leigh W. Simmons: Evolution
2008
XI. Conclusion
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Sexual Dimorphism
Sexual Selection
Males limited by access to mates
Females limited by resources
Exceptions
Universal, aspects found in plants and
animals
• YOU too may be a target for sexual selection
• Very Kewl