Radiation of the polymorphic Little Devil poison frog (Oophaga sylvatica) in Ecuador

Abstract

Some South American poison frogs (Dendrobatidae) are chemically defended and use bright aposematic colors to warn potential predators of their unpalatability. Aposematic signals are often frequency‐dependent where individuals deviating from a local model are at a higher risk of predation. However, extreme diversity in the aposematic signal has been documented in poison frogs, especially in Oophaga. Here, we explore the phylogeographic pattern among color‐divergent populations of the Little Devil poison frog Oophaga sylvatica by analyzing population structure and genetic differentiation to evaluate which processes could account for color diversity within and among populations. With a combination of PCR amplicons (three mitochondrial and three nuclear markers) and genome‐wide markers from a double‐digested RAD (ddRAD) approach, we characterized the phylogenetic and genetic structure of 199 individuals from 13 populations (12 monomorphic and 1 polymorphic) across the O. sylvatica distribution. Individuals segregated into two main lineages by their northern or southern latitudinal distribution. A high level of genetic and phenotypic polymorphism within the northern lineage suggests ongoing gene flow. In contrast, low levels of genetic differentiation were detected among the southern lineage populations and support recent range expansions from populations in the northern lineage. We propose that a combination of climatic gradients and structured landscapes might be promoting gene flow and phylogenetic diversification. Alternatively, we cannot rule out that the observed phenotypic and genomic variations are the result of genetic drift on near or neutral alleles in a small number of genes.

Phenotypic and genetic diversity in aposematic Malagasy poison frogs (genus Mantella)

“…Our results demonstrate that characterization of morphs based solely on observed phenotypic variation, especially when genetic structure is unresolved, can lead to an overestimation of the degree of polymorphism and/or polytypism that occurs in aposematic systems. Our findings are consistent with other studies in Neotropical poison frogs where sophisticated genetic datasets, utilized either in isolation or paired with morphological and ecological data, have revealed that a single species likely includes several distinct lineages (Posso‐Terranova & Andrés, ; Roland et al, ). Thus, overestimation of intraspecific variation and underestimation of species diversity in phenotypically diverse lineages may be more widespread than previously appreciated.…”

“…In systems with high color variability, however, determining whether color variants represent different species, different populations, or different morphs within populations is difficult particularly when genetic structure is not well resolved. Distinguishing between species, populations, and morphs can be especially challenging in phenotypically diverse poison frog groups, where high rates of phenotypic variation can confound our understanding of species delimitations (Posso‐Terranova & Andrés, ; Roland et al, ; Tarvin, Powell, Santos, Ron, & Cannatella, ).…”

“…In systems with high color variability, however, determining whether color variants represent different species, different populations, or different morphs within populations is difficult particularly when genetic structure is not well resolved. Distinguishing between species, populations, and morphs can be especially challenging in phenotypically diverse poison frog groups, where high rates of phenotypic variation can confound our understanding of species delimitations (Posso-Terranova & Andrés, 2018;Roland et al, 2017;Tarvin, Powell, Santos, Ron, & Cannatella, 2017). In many instances, the inability to distinguish whether color variation occurs within populations, between populations, or between species is further compounded by nonexistent or limited genetic datasets, which lack the resolution needed to clarify relationships among populations.…”

Molecular physiology of chemical defenses in a poison frog

“…Little devil (or diablito) frogs [Oophaga sylvatica (Funkhouser 1956) N=13] were collected during the day near the Otokiki Reserve (GPS coordinates: latitude 0.91075, longitude −78.57555, altitude 704 m) maintained by WIKIRI/Fundación Otonga in northwestern Ecuador in July 2013 (Roland et al, 2017). Frogs were individually stored in plastic bags with air and vegetation for 2-5 h. In the evening the same day of capture, adult frogs (over 1 yr of age; five females and three males) were anesthetized with a topical application of 20% benzocaine to the ventral belly and euthanized by cervical transection.…”

Molecular physiology of chemical defenses in a poison frog

“…Little Devil (or Diablito) frogs [Oophaga sylvatica, (Funkhouser) N=13] were collected during the day near the Otokiki Reserve (GPS coordinate: latitude 0.91075, longitude -78.57555, altitude 704m) maintained by WIKIRI/Fundación Otonga in northwestern Ecuador in July 2013 (Roland et al, 2017). Frogs were individually stored in plastic bags with air and vegetation for 2-5 hours.…”