Abstract
BackgroundPolytypism in aposematic species is unlikely according to theory, but commonly seen in nature. Ranitomeya imitator is a poison frog species exhibiting polytypic mimicry of three congeneric model species (R. fantastica, R. summersi, and two morphs of R. variabilis) across four allopatric populations (a "mimetic radiation"). In order to investigate chemical defenses in this system, a key prediction of Müllerian mimicry, we analyzed the alkaloids of both models and mimics from four allopatric populations.ResultsIn this study we demonstrate distinct differences in alkaloid profiles between co-mimetic species within allopatric populations. We further demonstrate that R. imitator has a greater number of distinct alkaloid types than the model species and more total alkaloids in all but one population.ConclusionsGiven that R. imitator is the more abundant species in these populations, R. imitator is likely driving the majority of predator-learned avoidance in these complexes. The success of Ranitomeya imitator as a putative advergent mimic may be a direct result of differences in alkaloid sequestration. Furthermore, we propose that automimicry within co-mimetic species is an important avenue of research.
Highlights
Polytypism in aposematic species is unlikely according to theory, but commonly seen in nature
The family Dendrobatidae contains a high diversity of frog species and alkaloids [11,12], providing a number of unique opportunities to study the link between aposematism and chemical defense
This difference was statistically significant in the Sauce banded morph of R. imitator and R. summersi (t8 = 4.451, p = 0.002) and the Varadero orange-headed morph of R. imitator and R. fantastica (t8 = 2.757, p = 0.025), and was suggestive of a trend in the Tarapoto spotted morph of R. imitator and R. variabilis (t8 = 1.857, p = 0.100) and the Pongo de Cainarachi striped population of R. imitator and R. variabilis (t8 = 1.549, p = 0.160; Figure 3)
Summary
Polytypism in aposematic species is unlikely according to theory, but commonly seen in nature. Ranitomeya imitator is a poison frog species exhibiting polytypic mimicry of three congeneric model species (R. fantastica, R. summersi, and two morphs of R. variabilis) across four allopatric populations (a "mimetic radiation"). Alkaloid defenses have been detected in five families of poison frogs: Dendrobatidae [1,3], Mantellidae [4,5,6], Bufonidae in the genus Melanophryniscus [6,7,8], Myobatrachidae in the genus Psuedophryne [6], and recently in diminutive Cuban members of Eleutherodactylidae [9]. The family Dendrobatidae contains a high diversity of frog species and alkaloids [11,12], providing a number of unique opportunities to study the link between aposematism and chemical defense. Alkaloid defenses in all poison frogs (including Dendrobatidae) are sequestered from an arthropod diet [3], consisting primarily of mites, ants, beetles, and millipedes (reviewed in [13]). Accompanying the ability to sequester alkaloid defenses, many species exhibit
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