Two-Way Selection for Aggression in Juvenile, Female and Male Sticklebacks (Gasterosteus Aculeatus L.), With Some Notes On Hormonal Factors

This paper summarizes some main results and conclusions of a behaviour genetic study on intraspecific aggressiveness in the three-spined stickleback (BAKKER, in press). Bidirectional selection experiments with aggressiveness in a number of test situations each serving as a criterion of selection, reveal that the phenotypic variation of aggressiveness in juvenile and adult females, in juvenile males, of territorial aggressiveness and dominance ability in reproductive males can to a considerable extent be ascribed to genetic variation. Selection for enhanced aggressiveness generally is less effective than for reduced aggression levels. In females the genetic influence on aggressiveness in the juvenile and adult stage is most likely identical. However, in males different manifestations of aggressiveness (as measured in a number of test situations), though covered by the functional Aggression-concept, by no means represent a unity, neither with respect to their genetic causation nor with respect to their hormonal causation.