Genetic differences and phenotypic plasticity as causes of variation in oviposition preference in Battus philenor.

Bradshaw (1965) proposed that phenotypic plasticity would be more common than adaptive genetic variability in species for which environmental fluctuations occur over periods roughly equal to that species' generation time. In an effort to examine this notion, sources of seasonal variation in two components of oviposition behavior in an east Texas population of pipevine swallowtail butterflies (Battus philenor) were investigated under natural and seminatural conditions. Variability in a visually-based prealighting component involving orientation to leaf shape was primarily due to phenotypic plasticity in the form of adult learning; no seasonally-based genotypic differences in leaf-shape discrimination behavior were observed. By contrast, a chemotactile post-alighting component involving elicitation of oviposition after landing on the host plant was not phenotypically plastic, i.e., not susceptible to learning. In addition, only slight and nonsignificant seasonally-based differences in post-alighting responses to different host species were observed.