Phenotypic plasticity in field populations of the tropical butterfly Hypolimnas bolina (L.) (Nymphalidae)

Phenotypic plasticity may enable organisms to maximize their fitness in sea sonally variable environments. However, in butterflies, seasonal polyphenis m is often striking but functionally obscure. This paper addresses the poss ible adaptive significance of phenotypic variation in the tropical butterfl y Hypolimnas bolina (L.) (Nymphalidae). Plasticity in body size and wing co loration can be elicited in this species under laboratory conditions, howev er it is not known how this plasticity is expressed in the wild. Moreover, adult H. bolina spend the winter dry season in a reproductive diapause, whi ch allows certain predictions regarding the occurrence of seasonal plastici ty. Based on consideration of the requirements of diapausing and directly d eveloping individuals, we predicted that if seasonal plasticity in phenotyp e were adaptive, then overwintering individuals should be larger and darker than their directly developing counterparts. This prediction was largely - although not entirely - fulfilled. Dry season butterflies were duller and darker than their wet season counterparts (this plasticity was superimposed on a genetic colour polymorphism), however size plasticity varied geograph ically. Dry season adults were consistently larger than wet season adults i n the tropical north, but not in the south. We use these findings to discus s the possible adaptive significance of seasonal variation in the colour an d size of this tropical butterfly. (C) 2001 The Linnean Society of London.