Distinct genetically based strategies vs. Conditional strategy

If the 3 types represent 3 distinct strategies, then:

  1. The differences between them should be genetic and 
  2. The mean reproductive success of the 3 types should be equal

Sperm Competition

  1. Some sperm can swim faster than other sperm
  2. Some sperm penetrates the egg better than other sperm 

Mate Guarding Males

  • Males guard and fight off other males so that the female can’t mate with more than one male

Mating Plug

  • Used when a males chances of mating again are low
    • If females are rare or widely dispersed

Female mate choice leads to the evolution of nuptial gift giving

Sexual Cannibalism

  • In some species, one sex (usually the female) consumes the other during sexual reproduction. 

Sexual Suicide

  • The ultimate nuptial gift

What leads to extreme male ornamentation and/or courtship display?

Good Parent Theory

  • Females prefer to mate with males that provide more paternal care 
  • Male courtship is linked to his parental abilities

Healthy Mate or Good Genes

  • Bright colors can indicate good foraging ability, good health, stronger immune system (can help raise young, females avoid diseases and parasites if they choose them)
  • Male inherited good traits from his father (so he can pass them to offspring)

Runaway Selection Theory

  • Female mate choice genes and genes for the preferred male attribute are inherited together.
  • Daughters inherit the genes for the mate preference, and sons inherit the preferred attribute (like bright tail in birds).
  • Males attract more females with the preference.
  • The mate preference “takes on a life of its own”.

Chase away selection theory (sensory exploitation)

viability selection on female sensory system——->Female attraction for a male trait that is absent(preexisting bias)——> Mutation produces a rudimentary male display trait (exploitation)——>Female fitness declines—–>Female mating threshold increases——> Male attraction declines——–> Exaggeration of male display——>Female fitness declines

Sexual Conflict

  • Females resist mating, often have the control over which males get to mate
  • Males develop traits that enhance his ability to mate, even if it lowers female fitness
    • (Forced copulations, infanticide, transfer of toxic compounds during mating)