Balanced polymorphisms and their divergence in a Heliconius butterfly.

James G Ogilvie,Steven Van Belleghem,Brian A Counterman,Riccardo Papa,Owen W Mcmillan,Ryan Range,Mathieu Chouteau

doi:10.1002/ece3.8423

Abstract

The evolution of mimicry in similarly defended prey is well described by the 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 among 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 among 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.

Highlights

The diversity of color patterns found in the Heliconius butterfly radiation is a striking example of the power of natural selection to generate biodiversity
Striking similarity of predation pressures across Heliconius species and populations Our results of predator attacks on Heliconius models correspond to the attack patterns observed in markrelease-recapture experiments, where naıve predators significantly attack novel, exotic patterns relative to native, common warning patterns (Mallet and Barton, 1989; Langham, 2004)
Attack percentages in these studies range from 4-15%, which overlaps our observed attack percentages that ranged from 4-12% on H. doris morphs

Summary

Introduction

The diversity of color patterns found in the Heliconius butterfly radiation is a striking example of the power of natural selection to generate biodiversity. As first described by Henry Walter Bates (1862), the genus clearly demonstrates a diverse array of warning color patterns established throughout several mimicry rings This presents a challenge to Muller’s theory which predicts that the selective pressures enacted by predators attacking novel color patterns should force the convergence of many warning signals into few recognizable color patterns. In contrast to this expectation, the co-mimics Heliconius erato andHeliconius melpomene diverged into over 25 geographic color pattern morphs. The Mullerian mimic Heliconius dorisis known for being polymorphic across its entire geographic distribution that spreads across most of South and Central America (Mallet, 1999; Constantino et al, 2005), with both red and blue color morphs found throughout its range. The Freeman–Tukey deviate (FT) was compared with an alpha from 0.05 to 0.01 criterion corrected for multiple comparisons using a Bonferroni correction, to identify which model morph was attacked significantly more or less than expected based on the null hypothesis of equal attack probability

Results

Discussion

Literature Cited