Lecture 23: Polyandry In Jacanas (A Case Study)

Front 1

What's the difference b/w sexual selection and natural selection?

Back 1

Sexual selection is selection for traits that affect an individual's mating success whereas natural selection refers to selection for all traits that promote an individual's overall survival and reproductive success.

Front 2

In most animal species, sexual selection operates more strongly on ________ than ________.

Back 2

males than females. Male RS, but not female RS, often depends upon the number of mates obtained. This is why darwin's 2 components of sexual selection are male-male competition and female choice of mates.

Front 3

What's an extreme example of reversed sexual selection? Explain their lifestyle.

Back 3

In Jacanas, males provide all incubation care of eggs and virtually all care of the young. It takes a male 3 months to rear one brood of young (during this time, he is not available to rear another).--females can lay clutches of eggs at a faster rate than males can take care of them-->shortage of 'available' males, and female RS is limited by access to such males.

Front 4

What are the consequences associated with this reversed sexual selection in jacanas?

Back 4

1) sexual dimorphism in body size (females much larger than males)
2) sexual dimorphism in weaponry (females = larger wing spurs than males)
3)Sexual dimorphism in ornamentation (females + larger and brighter facial shields than males)
4) sexual dimorphism in physical dominance (females are behviorally dominant)
5) sexual dimorphism in longevity (males live longer)

Front 5

What are the behavioral tactics of female jacanas?

Back 5

1) Females are territorial (fight to obtain and hold onto territories; size matters- larger females = larger territories)
2) females are infanticidal (destroy eggs and kill young of other females)--this occurs after a female takes over another female's territory
3) Some females polyandrous--maintain pair-bonds with more than one male (results in harems of males: this is called Simultaneous Polyandry)this is VERY prevalent.

4) females often 'multiply mate' (copulate with more than one male) MALES DO NOT HAVE PATERNITY ASSURANCE

Front 6

What are the best situations for males and females in a polyandrous group?

Back 6

1) for females, it is better to have more mates
2) for males, it is better to be monogamous

Front 7

Back to the asymmetrical game...who benefits more by deserting?

Back 7

female.. ALSO remember 2 parents are not necessarily better then 1 b/c the cost of care (shading, brooding etc) are not high.

Front 8

How do males increase assurecne of paternity?

Back 8

1) mate guard
2) copulate at high rate