DIFFERENT PATHWAYS IN ARTHROPOD POSTEMBRYONIC DEVELOPMENT.

To investigate the consequences of canalization and plasticity in arthropod developmental pathways, we developed a model that predicts eight possible combinations among three larval developmental parameters. From the descriptions of insect and spider postembryonic development, it is apparent that not all aspects of juvenile development are plastic and that species differ in which traits are plastic. Most strikingly, only four of the possible eight combinations of canalized and plastic parameters have been found in nature. Using this model, we show that the identity of the canalized developmental parameters and the degree of genetic variation in the value at which a given parameter is fixed have important implications for the ecology and evolution of complex life cycles. © 1996 The Society for the Study of Evolution.