Evolution of a snake mimicry complex Public Deposited

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  • March 20, 2019
Creator
  • Harper, George Raymond
    • Affiliation: College of Arts and Sciences, Department of Biology
Abstract
  • Batesian mimicry, the adaptive resemblance of harmless organisms (mimics) to harmful organisms (models) that causes predators to avoid both models and mimics, occurs in diverse taxa. Despite the fascination that mimicry complexes generate, many questions remain unanswered concerning the role of mimicry in evolution. My Ph.D. research has examined the evolution of a snake mimicry complex in the southeastern United States in which selection on the mimetic phenotype varies spatially in magnitude and direction. The mimic, harmless scarlet kingsnakes (Lampropeltis triangulum elapsoides), and the model, venomous eastern coral snakes (Micrurus fulvius), vary in absolute and relative abundance such that the model is more common deep within its range and the mimic is more abundant at the edge of the model's range. Also, despite selection against the mimetic phenotype outside the range of the model, the range of the mimic exceeds that of the model (an area termed allopatry). Therefore, I sought to determine: 1) what evolutionary mechanisms maintain the mimic in allopatry, 2) whether there has been an evolutionary response to selection against the mimetic phenotype in allopatry, and 3) whether spatial variation in the relative abundance of models and mimics leads to spatial variation in the degree to which mimics resemble the local model. A potential confounding factor in the evolution of the mimetic phenotype in L. t. elapsoides is interbreeding with non-mimetic conspecifics. Therefore, I looked for gene flow from non-mimetic conspecifics and examined the relationship between L. t. elapsoides and the rest of Lampropeltis. My results indicate that the best mimics occur at the edge of the model's range and that gene flow from there into allopatry maintains the mimetic phenotype in allopatry. Despite gene flow, selection against the mimetic phenotype is decreasing the resemblance between allopatric L. t. elapsoides and M. fulvius. Additionally, gene flow from non-mimetic L. triangulum is not altering the phenotype of L. t. elapsoides, and, in fact, the scarlet kingsnake diverged from other Lampropeltis millions of years ago. Thus, I recommend re-elevating the scarlet kingsnake to full species status and renew the use of L. elapsoides.
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  • Pfennig, David William
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