Diverse Evidence for the Decline of an Adaptation in a Coral Snake Mimic
Losses of adaptations in response to changed selective pressures are evolutionarily important phenomena but relatively few empirical examples have been investigated in detail. To help fill this gap, we took advantage of a natural experiment in which coral snake mimics occur on two nearby tropical islands, one that has coral snake models (Trinidad) and one that lacks them (Tobago). On Tobago, an endemic coral snake mimic (Erythrolamprus ocellatus) exists but has a relatively poor resemblance to coral snakes. Quantitative image analysis of museum specimens confirmed that E. ocellatus is a poor mimic of coral snakes. To address questions related to the functional importance of this phenotype, we conducted a field experiment on both islands with snake replicas made of clay. These results clearly indicated a strong inter-island difference in predator attack rates where snake replicas that resembled coral snakes received protection in Trinidad but not in Tobago. Further, a molecular phylogenetic analysis of the ancestry of E. ocellatus revealed that this poor coral snake mimic is deeply nested in a clade of good coral snake mimics. These data suggest that the lack of coral snakes on Tobago altered the selective environment such that the coral snake mimicry adaptation was no longer advantageous. The failure to maintain this ancestral feature in allopatry provides a compelling example of how losses of complex adaptations can occur.
KeywordsAllopatry Erythrolamprus Mimicry Loss Micrurus Reversal
We thank L. Fawcett, S. Hackel and D. Raines for help in the field and we acknowledge the Trinidad Department of Forestry and the Tobago Department of Natural Resources and the Environment for issuing research and collection permits. We extend appreciation to S. Mastrandrea, T. Mastrandrea, M. McCaffrey and M. Hodson for assisting greatly in the construction of the clay snakes. We thank G. Schneider (UMMZ), L. Vonnahme and D. Kizirian (AMNH) and K. de Queiroz and J. Poindexter (USNM) for museum specimen photographs. Thanks also go to the Royal Ontario Museum (R.W. Murphy), the California Academy of Science (J. Vindum) and the Louisiana State University Museum of Natural Science (D. Dittman) for tissue loans. The College of Wooster IACUC approved the methodologies used in this project. Funding was provided by the Henry Luce Fund, the Copeland Fund, and Presidential Discretionary Funds at The College of Wooster.
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interest.
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