Balanced polymorphisms and their divergence in a Heliconius butterfly

The evolution of mimicry in similarly defended prey is well described by
Müllerian mimicry theory, which predicts the convergence of warning
patterns in order to gain the most protection from predators. However,
despite this prediction, we can find great diversity of color patterns
amongst Müllerian mimics such as Heliconius butterflies in the neotropics.
Furthermore, some species have evolved the ability to maintain multiple
distinct warning patterns in single populations, a phenomenon known as
polymorphic mimicry. The adaptive benefit of these polymorphisms is
questionable since variation from the most common warning patterns is
expected to be disadvantageous as novel signals are punished by predators
naive to them. In this study we use artificial butterfly models throughout
Central and South America to characterize the selective pressures
maintaining polymorphic mimicry in Heliconius doris. Our results highlight
the complexity of positive frequency-dependent selection, the principal
selective pressure driving convergence amongst Müllerian mimics, and its
impacts on interspecific variation of mimetic warning coloration. We
further show how this selection regime can both limit and facilitate the
diversification of mimetic traits.