Preference Variation in the Polyphagous Tiger Swallowtail Butterfly (Lepidoptera: Papilionidae)

For polyphagous insect species, variation in oviposition preference often sets the boundaries within which host use patterns can evolve. Ultimately, host choice is a function of genetic predisposition, physiological state, and past experiences of ovipositing females. Here we explore preference variation among female tiger swallowtail butterflies, Papilio glaucus L., to investigate rank-order and specificity changes caused by genetic and environmental influences. Hosts differed in their overall relative acceptability to ovipositing females. Preference variation among females was extensive, however, and expressed as both differences in relative fidelity to particular hosts and differences in the host most preferred. Subsequent analysis of 2 of these hosts indicated that heritable variation among females was associated with differences in specificity toward the less preferred host rather than how females ranked the hosts. Thus, preference hierarchies should be conserved among P. glaucus populations encountering different host environments. This result is consistent with patterns we reported earlier for regional P. glaucus populations. Evidence of apparent links between female preference and factors unrelated to host-choice per se suggest that host-choice behavior is labile. Patterns of egg distributions across hosts will thus not necessarily reflect adaptive responses and optimal behaviors. We discuss our findings with respect to adaptation and evolution of host use patterns in P. glaucus.