Chromosomal polymorphism, morphological traits and male mating success in Leptysma argentina (Orthoptera).

Leptysma argentina (Acrididae: Orthoptera) is polymorphic for a centric fusion between pairs 3 and 6 of its basic chromosomal complement. With the aim of carrying out an analysis of selection components in this species, male mating success, in relation to karyotype and three morphometric traits, was assessed by using experimental contests with four males and one female per mating cage. Karyotype was assessed in terms of fused chromosome 3/6 dosage and coded as "0", "1" and "2" for unfused homozygotes, heterozygotes and fusion homozygotes, respectively. The individual ANOVA showed significant differences between "successful" and "unsuccessful" males in all four measured characters. Fusion carriers showed a higher relative fitness. Since the phenotypic correlations among traits were significant, the selective effects were assessed by means of a multivariate analysis, which demonstrated that selection acted significantly on femur length only, selection on karyotype being indirect. Given that the fusion frequency has been constant since 1985, the presence of selective trade-offs cannot be ruled out.