Tracking the evolution of warning signals

EVOLUTIONARY studies are hampered by a lack of experimental ways in which to test past events such as the origination of aposematism(1-7), whereby unpalatable or poisonous prey signal their unprofitability, often by being warningly coloured, Inexperienced predators do learn to avoid unpalatable prey as a result of such signals(8-10), hut in addition there may be an inherited cautiousness about attacking when common or conspicuous warning signals are evident(11-16). As current predators are not naive in the evolutionary sense, it is still not resolved(3-7,17,18) whether aposematism originated only in aggregations of prey(19,20) or among solitary prey as well(21-23). Here we explore this controversy in evolutionarily naive predators by creating a novel world with warning signals not found in the environment. Initially, the aggregation of prey favoured the warning signals supporting Fisher's view(24) of kin aggregations as the evolutionary starting point of aposematism, However, once predators had experienced warning signals, pre-existing avoidance seemed to facilitate evolution of Mullerian mimicry complexes(25) with similar types of signals even among solitary prey.