Development time integrates temperature and host plant cues for eyespot size in three tropical satyrine butterflies

Abstract

Many tropical butterflies have distinct wet and dry season adult morphs differing in the size of wing eyespots. Eyespot size is influenced by the environment experienced by developing larvae, and this plasticity is adaptive because the morphs have higher survival in their respective seasons. Higher temperature during the larval phase produces adults with larger eyespots in many species. This reaction norm is adaptive when high temperatures precede the wet season, which is not the case in all regions. Therefore, butterflies may rely on another environmental cue such as host plant species, and may also integrate information from multiple environmental variables through their combined effect on larval developmental time. To test this, we manipulated developmental time of sympatric populations of three butterflies − Ypthima huebneri, Mycalesis mineus and Melanitis leda − using combinations of temperatures and host plant species. Higher rearing temperature correlated with larger eyespot size in all species. Host plant species independently affected eyespot size. The effects of temperature and host plant differed between species, sexes, and between the forewing and hindwing, suggesting differential selection pressures on eyespots. Nevertheless, information about temperature and host plant species may be integrated through developmental time, because shorter larval development time was correlated with larger eyespots in adults. However, there were exceptions within specific treatments, species, and eyespots. Our results highlight the complex control of eyespot size, which is likely influenced by a network of interacting factors. Our study also demonstrates how sympatric populations of different species interpret similar environmental cues differently.