Exploring Mimetic Diversity in West African Forest Butterflies

Abstract

In a small area of secondary rain forest in West Africa there is an assemblage of mimetic butterflies based on two colour combinations: dark brown and orange, and black and white. The models are species of unpalatable Danaidae and Acraeidae, the mimics species and polymorphic forms of Nymphalidae, Satyridae, Papilionidae, and Lycaenidae. The models are about five times as abundant as the mimics but difficulties in correlating the frequency of particular mimics with models arise because of difficulties in taking random samples. Males of the principal species of models appear more active than females and are more often encountered, but females of the most important mimic are encountered more often than males. This apparent difference in flight activity between sexes is important as some polymorphic forms of the most abundant mimic are sexlimited. Whether predators encounter the sexes of models and mimics at different frequencies is conjectural. An attempt is made to express mimetic diversity by using an information theory index of species diversity, although no changes in diversity were found during 45 days of continuous sampling. Unexpectedly, mimics seem consistently more diverse than models. Although an entire forest assemblage of mimetic butterflies has been analysed quantitatively, the situation is extremely complex and an understanding of mimetic diversity may only be possible with a detailed knowledge of the ecology of the species encountered.