Multiple selective pressures apply to a coral reef fish mimic: a case of Batesian-aggressive mimicry

Mimics closely resemble unrelated species to avoid predation, capture prey or gain access to hosts or reproductive opportunities. However, the classification of mimicry systems into three established evolutionary mechanisms (protection, reproduction and foraging) can be contentious because multiple benefits may be gained by mimics, causing the evolution of such systems to be driven by more than one selective agent. However, data on such systems are generally speculative or anecdotal. This study provides empirical evidence that dual benefits apply to a coral reef fish mimic in terms of increased access to food (aggressive mimicry) and reduced predation risk (Batesian mimicry). Bicolour fangblennies Plagiotremus laudandus gained access to more reef fish victims, which they attack to feed on fins and scales, when they spent more time associated with their model Meiacanthus atrodorsalis. Furthermore, exact replicas of P. laudandus incurred fewer approaches from potential predators compared with control replicas that varied in resemblance to P. laudandus. Predators with trichromatic visual systems (three distinct spectral sensitivities) could potentially distinguish between replicas based on colour based on theoretical vision models. Therefore, this mimicry system could be best described as Batesian-aggressive mimicry in which mimicry evolution is driven by multiple simultaneous selective pressures.