Sex roles and sexual selection

Sexual Selection has been portrayed as acting predominantly on males who co mpete with each other over copulatory access to females; selection was cons idered to be driven by females choosing between males at the pre- or postco pulatory level. However, a broader view of sexual selection is now emerging . Examining male discrimination between females and female-female competiti on has been beneficial in identifying factors influencing the direction and strength of sexual selection. Furthermore, consideration of processes such as sexual coercion or genetic incompatibility, which indirectly influence an individual's set of copulation partners, gamete set or their offspring s uccess, has helped to clarify the ways in which sexual selection may operat e. Moreover, there is increasing evidence that not all copulations translat e directly to paternity and that paternity does not necessarily translate i nto successful offspring. Postcopulatory and postfertilization mechanisms t hat influence not only paternity share but offspring recruitment now requir e further consideration. The benefits to each sex of copulating with partic ular partners or with more than one partner remains an area of debate. More carefully designed studies which eliminate alternative possibilities or qu antify the relative importance of different selective pressures will also b enefit from considering that not all copulations function solely to insemin ate or receive sperm. It is also now clear that not all individuals of one sex follow the same strategy. Examining the variation between individuals i n reproductive behaviour, fertilization success and offspring success will be important in establishing the selective pressures and mechanisms underly ing the operation of sexual selection. (C) 1998 The Association for the Stu dy of Animal Behaviour.