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Sexual Selection. Sexual dimorphism is common. Parental investment often differs between the sexes. Male and female seahorses which sex should be competitive and which choosy?. Strategies for the competitive sex often come at a cost. Strategy: Mate a lot!

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Sexual Selection


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slide7

Male and female seahorses

which sex should be competitive and which choosy?

strategies for the competitive sex often come at a cost
Strategies for the competitive sex often come at a cost

Strategy:

Mate a lot!

(Even at the cost of long-term survival)

slide10

Galapagos marine iguana

Cold water has algae

Return to land to warm up and digest

Big body allows more efficient grazing

Small body has a better metabolic “balance”

slide11

* = largest body size at which iguanas could maintain weight in two different years

Males lost weight, females were near optimum body weight

slide14

Bigger males got better territories

The most successful male, iguana 59, got more than four times as many copulations as any of his rivals

strategy 2
Strategy 2
  • Advertise
slide16

Bright coloration comes at a cost (higher predation on males)

Male and Female collared lizards

slide17

Male is more vulnerable to predators

Male must expend energy on tail

slide18

Body condition of males declines over season

Experimentallyshortened tails  Less decline in body condition

Therefore, long tails do have a cost!

slide19

Females didn’t like the shortened tails even though the treatment improved the health of the experimental males over the season

Is this choice good for the species?

Can the choice be good for a particular female?

(yes, if the male has good genes or if her sons are attractive)

From Pryke and Andersson (2005).