Directional selection on body weight and hybrid dysgenesis in Drosophila melanogaster

Abstract

The influence of transposable elements in generating variation for body weight of Drosophila melanogaster was investigated by comparing the response to artificial divergent selection in dysgenic and nondysgenic crosses using 2 independent systems of hybrid dysgenesis (PM and IR). Two replicates of initially dysgenic or nondysgenic crosses between Furnace Creek (IP) and Gruta (RM) strains were selected for increased and decreased body weight during 13 generations. A greater divergence in selection response was observed for the dysgenic lines than for the non dysgenic lines, but this difference disappeared when selection was relaxed. The selected lines were analysed at generation 13 with respect to their dysgenesis properties, as well as to the number and nature of their P and I elements. There was no correlation between the characteristics of the P and I elements in the selected lines and the intensity of response to selection for body weight. In both types of crosses, hybrid dysgenesis induced modification in body weight variance, probably by I and P-induced mutations. hybrid dysgenesis / PM and IR systems / body weight / Drosophila melanogaster Resume Selection directionnelle sur le poids des adultes et dysgenese des hybrides chez Drosophila melanogaster. L 'aptitude des elements transposables a generer de la variabilite pour le caractere poids des adultes chez Drosophila melanogaster, et donnant ainsi une plus grande prise a la selection, a ete et'udiee en comparant la reponse a une selection bidirectionnelle suivant que le croisement originei etait ou non dysgenique visa -vis des systemes PM et IR de dysgenese des hybrides. Deux repliques de chaque type de croisement (dysgenique ou non dysgenique) ont ete realisees entre les souches Furnace Creek (IP) et Gruta (RM), puis une selection bidirectionnelle a ete appliquee pour un poids eleve des adultes ou pour un poids faible. Une plus grande divergence de reponse a la selection a eU observee lorsque le croisement initial etait dysgenique par rapport au cas ou il etait non dysgenique. Mais cette difference disparait quand la pression de selection est rela.ckee. En fin de selection (generation 13), les lignees selectionnees ont eM