Comprehensive DescriptionRead full entry
Ranitomeya imitator is a small frog, with adults ranging from 17 to 22 mm (Symula et al. 2001). Dorsal skin is granular (Schulte 1986). The first toe is clearly differentiated (Schulte 1986). Digital discs are expanded as with other dendrobatids, with finger discs being at least twice the width of the finger base (Schulte 1986). Coloration is quite variable depending on the population, as this species mimics both color and pattern of several other sympatric (co-occurring) species of poison frogs (Symula et al. 2001).
Ranitomeya imitator near Tarapoto, Peru, closely resembles the sympatric species Ranitomeya variabilis (Schulte 1986; Symula et al. 2001). Both species have yellow reticulation over a black background on the head, dorsum, flanks, and forearms, resulting in the appearance of large black patches surrounded by yellow (Schulte 1986; Symula et al. 2001). On the venter and legs, both species have blue-green reticulation over a black background, resulting in the appearance of small black patches surrounded by blue-green (Schulte 1986; Symula et al. 2001). They can be distinguished by the patterning of the black spot on the nose; in R. imitator this spot is split in half by gold reticulation, whereas it is solid in R. variabilis (Schulte 1986; Symula et al. 2001). In addition, differences in calls and in egg coloration distinguish the two species (Symula et al. 2001).
In Huallaga Canyon, Peru, Ranitomeya imitator resembles a sympatric population of Ranitomeya fantastica (Symula et al. 2001). Both species in this area have a black ground coloration with yellow stripes, several of which are transverse, running across the body from side to side and extending down the arms and legs and across the midsection (as seen in the photos in Symula et al. 2001). However, R. imitator is smaller and has different ventral coloration and pattern, as well as a different call (Schulte 1986).
Near Yurimaguas, Ranitomeya imitator mimics Ranitomeya ventrimaculata (Symula et al. 2001). These frogs share the coloration pattern of thin longitudinal yellow stripes on a black background, over the head, dorsum, and flanks, while the legs have blue-green reticulation over a black background, resulting in the appearance of small black patches surrounded by blue-green color (as seen in the photos in Symula et al. 2001). Here again Ranitomeya imitator appears to be distinguishable by having a black spot on the tip of the snout bisected by a gold stripe. Male calls also differ between the two species (Symula et al. 2001).
This species is unusual in its mimicry of other species. It mimics not one but three other species of highly toxic poison frogs (Ranitomeya fantastica, Ranitomeya variabilis, and Ranitomeya ventrimaculata). This represents the only known example of mimetic radiation in amphibians, where different populations within a single species mimic several other species in appearance. In each case, a population of R. imitator is sympatric with a population of one of the other dendrobatid species, and looks virtually identical. Despite the similar appearances, in each case the two sympatric species can be distinguished by male calls and by egg coloration (Symula et al. 2001). The R. imitator populations have been confirmed by molecular phylogenetic analysis to be closely related members of a single species (Symula et al. 2001).
Because both species are toxic in each case, and both benefit from the resemblance, this is an example of Müllerian mimicry.In 2011, the genus Dendrobates was subdivided into seven genera, including the new genus Ranitomeya by Brown et al (2011).