SEXUAL CONFLICT - MALES WITH HIGHEST MATING SUCCESS CONVEY THE LOWESTFERTILIZATION BENEFITS TO FEMALES

In natural populations of a coral reef fish (the bluehead wrasse, Thal assoma bifasciatum), males with the highest daily mating success produ ce the fewest sperm per mating, and this is reflected in significantly lower fertilization rates. The average amount released by males in pa ir-mating was 3.3 x 10(6) spermatozoa, resulting in a fertilization ra te of 96%. Sperm released per spawn declined with increasing mating su ccess, so that females mating with the most successful males had less than 93% of their eggs fertilized. It is unlikely that high mating-suc cess males are physiologically incapable of increasing sperm productio n, because younger males with different mating strategies have absolut ely larger testes and higher daily sperm output. Feeding experiments s uggest that high-success males are diverting energy from gamete produc tion to other fitness-enhancing activities such as mate guarding. Fema les incur the cost of low sperm release by having fewer of their eggs fertilized. There are no obvious compensatory benefits to females from mating with high-success males.