Life imperfectly imitates life

Abstract

Some species evolve to resemble another species so as to protect themselves from predation, but this mimicry is often imprecise. An analysis of hoverflies suggests why imperfect imitation persists in the face of natural selection. See Letter p.461 Batesian mimics are potential prey species that are harmless to predators but gain protection through a resemblance to unpalatable prey species. Surprisingly, many Batesian species seem to be fairly mediocre mimics, despite presumably strong evolutionary pressure to improve the resemblance. This paper presents a morphological and phylogenetic analysis of harmless hoverfly species that mimic — with various degrees of success — stinging hymenopteran species. The authors rule out several hypotheses, such as that the imperfect mimicry is an artefact of human perception and that the imperfect mimics are actually hedging their bets by resembling several hymenopteran species at the same time. Instead, the authors find a link between imperfect mimicry and small body size, which suggests that the imperfect mimics are simply not subject to particularly intense selection.