REPRODUCTIVE ISOLATION AND MIMETIC DIVERGENCE IN THE POISON FROG RANITOMEYA IMITATOR

Abstract

Understanding the process of speciation requires examination of various stages of its progress. This work focuses on the early stages of population divergence, where populations of a single species may show varying levels of incipient reproductive isolation. This work focuses on a species of poison frog, Ranitomeya imitator, that has undergone population divergence in color pattern to mimic different model species. This is an example of a Müllerian mimetic radiation, which has led to the establishment of four distinct morphs of R. imitator occurring in different geographic areas. There are two main goals of this research: (1) to examine to what extent (if any), different mimetic morphs are reproductive isolated, and (2) to examine factors influencing variation in the strength of between-morph reproductive isolation. To do this, the work focuses on sampling across three mimetic transition zones. In Chapter 1, by using a combination of color pattern quantification, landscape genetics, and mate choice experiments, results show that a mimetic shift in R. imitator is likely driving incipient speciation among two of these mimetic morphs. In Chapter 2, two additional mimetic transition zones are studied. Results suggest that these mimetic morphs are strongly differentiated in aspects of the mimetic phenotype, but show little neutral genetic divergence, and random mating with respect to mimetic morph at the transition zones, suggesting that mimetic divergence has failed to generate reproductive isolation in the two transition zones studied in this chapter. It is suggested that multifarious selection on both mimetic color-pattern and body size may be responsible for explaining variation in progress toward speciation. In Chapter 3, variation in mating calls among mimetic morphs is studied. While there are shifts in certain aspects of the mating call across two mimetic transition zones, phonotaxis trials indicate that call differences among morphs may not be responsible for generating reproductive isolation. Overall, the this dissertation work supports the idea that mimicry may be driving speciation in Ranitomeya imitator, and provides a basis for future work examining ecological speciation in this system.