by Greg Mayer
Continuing with the frog theme, here are two representatives of Dendrobates pumilio, the strawberry poison dart frog, from Costa Rica.
As the word “poison” in their vernacular name indicates, these frogs are toxic, and their bright coloration is aposematic: it advertises the toxicity of the frog, and protects them from predators. They may often be seen wandering boldly about the rain forest floor in daylight. These two individuals show much of the range of color variation in the species: red backs with more or less darker speckling, and blue on the extremities ranging from the whole limb to just a hint on the toes and vent.
In northwestern Panama, however, in the region of Bocas del Toro, there are many color morphs– yellows, blues, blacks, greens– some of which are cryptic (i.e. camouflaged), rather than aposematic. In a paper last year (abstract only), Ian Wang and Brad Shaffer of UC-Davis studied the within-species phylogeny of these color morphs, and found that apparently cryptic forms had arisen multiple times. They proposed that this convergence in coloration might be driven by selection. But they admit much more work must be done:
The dramatic level of color polymorphism in the Bocas del Toro populations of D. pumilio remains difficult to explain, especially because our phylogeographic study of color evolution indicates a complex history of color changes.