THE EFFECTS OF LARVAL DENSITY ON GENETIC-VARIATION AND COVARIATION AMONG LIFE-HISTORY TRAITS IN THE BEAN WEEVIL (ACANTHOSCELIDES-OBTECTUS SAY)

It is generally assumed that the traits leading to higher fitness are different in crowded and uncrowded environments. This study concerns the genetic variation and covariation in life-history traits of the dry bean weevil (Acanthoscelides obtectus Say) reared under low and high densities. We have demonstrated that larval crowding has genotype-specific effects on life-history traits of the weevils. Our data suggest that the genetic covariance structure among life-history traits is very sensitive to density and that geno-type-density interactions affect the genetic correlations. It seems that the maintenance of genetic polymorphism in bean weevil populations may depend in part on the reversal of fitness order at different densities. We did not detect any significant correlation between plasticity and genetic variation of the life-history traits, which suggests that selection producing changes in the two types of variation can act independently.