Mechanisms for color convergence in a mimetic radiation of poison frogs

<p class="western"><span>In animals, bright colors </span><span>often evolve to mimic other species when a resemblance is selectively favored. </span><span>Understanding the </span><span>proximate </span><span>mechanisms </span><span>underlying </span><span>such </span><span>color mimicry can give insights into how mimicry evolves, for example, whether </span><span>color convergence </span><span>evolve</span><span>s</span><span> from a shared set of mechanisms or through the evolution of novel color production mechanisms. </span><span>W</span><span>e studied color production mechanisms in poison frogs (Dendrobatidae), focusing on the mimicry complex of </span><i>Ranitomeya imitator</i><span>. Using </span><span>reflectance spectrometry, skin pigment analysis, electron microscopy, and color modeling, </span><span>we found that</span><span> </span><span>the bright colors of these frogs, both within and outside the mimicry complex, are</span><span> </span><span>largely </span><span>structural </span><span>and</span><span> </span><span>produced by</span><span> iridophores, </span><span>but </span><span>that color production depends</span><span> crucially on interactions with pigments. </span><span>Color variation </span><span>and mimicry </span><span>is regulated predominantly by iridophore platelet thickness </span><span>and, to a lesser extent, concentration of the red pteridine pigment drosopterin</span><span>. </span><span>Compared to </span><span>each of </span><span>the </span><span>four morphs of </span><span>model species which it resembles, </span><i>R. imitator </i><span>displays greater variation </span><span>in </span><span>both structural and pigmentary mechanisms, which </span><span>may have </span><span>facilitated phenotypic divergence in this species</span><span>. </span><span>Analyses of non-mimetic dendrobatids </span><span>in other genera demonstrate</span><span> </span><span>that </span><span>these </span><span>mechanisms are </span><span>widespread</span><span> within </span><span>the family,</span><span> </span><span>and </span><span>that</span><span> poison frogs share a </span><span>complex</span><span> physiological "</span><span>color </span><span>palette" </span><span>that can produce diverse and highly reflective colors</span><span>.</span></p>