Elsewhere across its range, the Strawberry Poison frog (Oophaga pumilio) lives up to its name, but in the Bocas del Toro archipelago of Panama, it exhibits striking variation in coloration. This diversity is puzzling: these populations have not been isolated for long, as the archipelago formed only a few thousand years ago through sea-level rise, and we usually expect that aposematic coloration—which warns predators of toxicity—should evolve to become more similar rather than more different over time. This paradox is the focus of Aguilar et al. (2026), who combine sequencing, microscopy, and pigment composition analyses to uncover the genetic and cellular basis of color variation in these frogs. Their work reveals multiple mechanisms underlying blue, red, orange, yellow, and green morphs. For example, the gene kit, which regulates the development, survival, and migration of pigment cells, appears to play a key role in producing blue coloration, and may explain why blue frogs possess more dark pigment cells closer to the skin surface. The study further shows that many color-associated variants pre-date the most recent formation of the island system. Given repeated cycles of island formation and reconnection driven by fluctuating sea levels, the authors propose a "morph pump" hypothesis, in which historical connectivity repeatedly shuffled color alleles among populations, helping maintain variation over time. Finally, they find evidence that rare color morphs have been favored by selection in Bocas del Toro. Clearly, this isn't true across the rest of this frog's range, so why that's the case remains to be seen!

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