Seasonal polyphenism in body size and juvenile development of the swallowtail butterfly Papilio xuthus (Lepidoptera: Papilionidae)

Shinya Komata,Teiji Sota

doi:10.14411/eje.2017.046

Abstract

Seasonal polyphenism in adults may be a season-specific adaptation of the adult stage and/or a by-product of adaptive plasticity of the juvenile stages. The swallowtail butterfly Papilio xuthus L. exhibits seasonal polyphenism controlled by photoperiod. Adults emerging in spring from pupae that spend winter in diapause have smaller bodies than adults emerging in summer from pupae that do not undergo diapause. Pupal diapause is induced by short-day conditions typical of autumn. To explore the interactive effects of temperature and developmental pathways on the variation in adult body size in P. xuthus, we reared larvae at two temperatures (20°C, 25°C) under two photoperiods (12L : 12D and 16L : 8D). Pupal weight and adult forewing length were greater in the generation that did not undergo diapause and were greater at 25°C than at 20°C. Thus, body size differences were greatest between the individuals that were reared at the longer day length and higher temperature and did not undergo diapause and those that were reared at the shorter day length and lower temperature and did undergo diapause. Unlike in other Lepidoptera, larvae of individuals that undergo diapause had shorter developmental times and higher growth rates than those that did not undergo diapause. This developmental plasticity may enable this butterfly to cope with the unpredictable length of the growing season prior to the onset of winter. Our results indicate that there are unexplored variations in the life history strategy of multivoltine Lepidoptera.

Highlights

Temperate insects must cope with environmental seasonality
It is necessary to study adult seasonal polyphenism from the viewpoint of adaptation and constraints at the juvenile stage because variations in some adult traits may reflect those in juvenile development and growth patterns
The objective of this study was to clarify whether there is a difference in development times and growth rates between generations that undergo and do not undergo diapause, and whether temperature during larval development affects the variation in adult body size in P. xuthus

Summary

Introduction

A notable feature of seasonal adaptation in multivoltine species is seasonal polyphenism, defined as seasonal phenotypic variations among generations attributable to phenotypic plasticity (Shapiro, 1976; Lively, 1986; Moran, 1992). In many butterflies, such polyphenism involves seasonal variation in adult phenotypes, including wing pattern, body size (wing length), and behaviour. These differences may be attributable to the adaptation of adults and/or may be by-products of adaptation and constraints in juvenile stages (Gotthard & Nylin, 1995; Brakefield & Frankino, 2009; Friberg & Karlsson, 2010). Variation in adult body size may be caused by differences in juvenile development and growth, and may be related to adaptive “growth decisions” (Gotthard, 2008) made when seasonal conditions are variable

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