ABSTRACT
Genetic parameters were assessed in the nonmigratory Puerto Rico population of the milkweed bug, Oncopeltus fasciatus, and compared with parameters estimated in a migratory population from Iowa (Palmer and Dingle, 1986). Offspring-parent regression analysis provided initial estimates of heritabilities and phenotypic and genetic correlations among wing length, head-capsule width, female age at first reproduction, fecundity for the first and second five days of reproduction by females, and clutch size for the first and second five days of reproduction by females. Replicated bidirectional selection for wing length was then imposed, with a direct response to selection revealing substantial additive genetic variance for this trait, as was also the case with the Iowa population. Assays for correlated response to selection yielded two further similarities to Iowa: a positive response in head-capsule width and no consistent response in age at first reproduction. In contrast to the results with Iowa bugs, neither regression analysis nor selection revealed statistically significant genetic correlations between fecundity measures and those of other traits. In both populations the potential exists for body-size characters to evolve together independently of age at first reproduction; but in the nonmigratory Puerto Rico bugs, fecundity does not contribute to a life-history syndrome involving genetic correlations among these traits.
ABSTRACT
Offspring-parent regressions provided initial estimates of heritabilities and genetic correlations among wing length, body length, pronotum width, head-capsule width, development time, age at first reproduction, and fecundity in an Iowa population of the large milkweed bug, Oncopeltus fasciatus. Replicated, bidirectional selection for wing length was imposed for nine generations. The direct response to selection revealed the existence of substantial additive genetic variance for wing length in this population. Traits were assayed for correlated responses to selection after seven generations. Body length, pronotum width, head capsule width, and fecundity showed consistent, positive correlated responses. Development time showed a negative correlated response. Age at first reproduction showed no consistent correlated response to selection on wing length. These pleiotropic effects among wing length and fecundity, development time, and body size characters provide the potential for these traits to evolve together in O. fasciatus, independently of age at first reproduction.
