Evolutionary transitions from camouflage to aposematism: Hidden signals play a pivotal role

The initial evolution of warning signals in unprofitable prey, termed aposematism, is often seen as a paradox because any new conspicuous mutant would be easier to detect than its cryptic conspecifics and not readily recognized by naive predators as defended. One possibility is that permanent aposematism first evolved through species using hidden warning signals, which are only exposed to would-be predators on encounter. Here, we present a large-scale analysis of evolutionary transitions in amphibian antipredation coloration and demonstrate that the evolutionary transition from camouflage to aposematism is rarely direct but tends to involve an intermediary stage, namely cryptic species that facultatively reveal conspicuous coloration. Accounting for this intermediate step can resolve the paradox and thereby advance our understanding of the evolution of aposematism.

Automated summary

The initial evolution of aposematism in unprofitable prey is considered a paradox, but it is suggested that hidden warning signals may have played a role. This study examines amphibian antipredation coloration and finds that the transition from camouflage to aposematism often involves an intermediate stage of cryptic species. Accounting for this intermediate step can help explain the evolution of aposematism.