The Environmental and Genetic Control of Seasonal Polyphenism in Larval Color and Its Adaptive Significance in a Swallowtail Butterfly

Abstract

Seasonal polyphenism, in which different forms of a species are produced at different times of the year, is a common form of phenotypic plasticity among insects. Here I show that the production of dark fifth-instar caterpillars of the eastern black swallowtail butterfly, Papilio polyxenes, is a seasonal polyphenism, with larvae reared on autumnal conditions being significantly darker than larvae reared on midsummer conditions. Both rearing photoperiod and temperature were found to have individual and synergistic effects on larval darkness. Genetic analysis of variation among full-sibling families reared on combinations of two different temperatures and photoperiods is consistent with the hypothesis that variation in darkness is heritable. In addition, the genetic correlation in larval darkness across midsummer and autumnal environments is not different from zero, suggesting that differential gene expression is responsible for the increase in larval darkness in the autumn. The relatively dark autumnal form was found to have a higher body temperature in sunlight than did the lighter midsummer form, and small differences in temperature were found to increase larval growth rate. These results suggest that this genetically based seasonal polyphenism in larval color has evolved in part to increase larval growth rates in the autumn.

Carotenoid‐based colour polyphenism in a moth species: search for fitness correlates

“…Nevertheless, our results suggest that the evolution of coloration in O. antiqua is not likely to be constrained by biochemically mediated trade-offs but is solely driven by ecological factors instead. The likely mechanisms could be related to thermoregulation (Gunn, 1998;Hazel, 2002), or varying predation pressure against different colour morphs in space and time (Endler & Mappes, 2004). The association of colour morph with larval age (Figure 1) supports the idea of a decisive role of bird predation: it is reasonable to assume that the effectiveness of any colour pattern in defence against visually searching predators is dependent on the size of the prey (Gamberale & Tullberg, 1996).…”

“…As a proximate explanation, the existence of different morphs may be directly connected to pigment concentration in larval host plants (Burghardt et al, 2001;Eichenseer et al, 2002). The ultimate causes of maintenance of variable coloration may be related to the purpose of camouflage (Greene, 1989;Merilaita et al, 1999) or thermoregulation (Gunn, 1998;Hazel, 2002;Solensky & Larkin, 2003). The ultimate causes of the frequently observed effect of larval crowding remain unclear (Wilson & Reeson, 1998;Wilson et al, 2001).…”

Phenotypic plasticity, but not adaptive tracking, underlies seasonal variation in post‐cold hardening freeze tolerance of Drosophila melanogaster

“…While phenotypic variation can arise as a result of environmentally triggered plasticity, genetic variation in seasonally advantageous traits also exists (Dobzhansky & Ayala, 1973;reviewed in Tauber &Tauber, 1981 andWilliams et al, 2017). Therefore, genotypes that underlie variation in seasonally relevant phenotypes may change in frequency across seasonal timescales for short-lived organisms (Behrman, Watson, O'Brien, Heschel, & Schmidt, 2015;Grosberg, 1988;Hazel, 2002;King, 1972;Schmidt & Conde, 2006). In the present study, we examine the relative importance of plasticity and rapid, seasonal adaptation in the cold tolerance of Drosophila melanogaster.…”

Mechanisms of Color Production in a Highly Variable Shield-Back Stinkbug, Tectocoris diopthalmus (Heteroptera: Scutelleridae), and Why It Matters

“…Pigmentary colors can also be sensitive to rearing conditions, and the reliance on melanin pigment as a major component may make the patches even more sensitive to environmental disturbance. For example, cuticular melanization can be upset by high temperatures in many taxa including Lepidoptera [64], Drosophila flies [26], and other Heteroptera [25]. This can help explain population differences, with high ambient temperatures suppressing the patches in tropical populations [34], and depending on the window of susceptibility, can also be contributing to intrapopulation variation, via seasonal or daily fluctuations in temperature [33].…”