Factors affecting the evolution of mimicry

Abstract

Mimicry, where an undefended species resembles a defended species (Batesian mimicry) or where two or more defended species resemble one another (Müllerian mimicry) is one of the most fascinating examples of natural selection in nature. However, even after more than 150 years of research, there are still outstanding questions. One of the biggest of these is: Why do some mimics resemble their models more closely than others? Several hypotheses have been proposed to explain this, yet few have been tested experimentally. To do this, I collected images of museum specimens of real-life model-mimic pairs using a hyperspectral scanner. I then analysed these images to measure the similarity of model-mimic pairs to a potential avian predator. I then investigated how these measures were affected by three factors which have previously been suggested to influence mimetic similarity: the palatability of the mimic, the climate of the area where the mimic is found and the size of the mimic. None of these factors had a significant effect on any measures of similarity. I then performed two behavioural experiments using domestic chicks (Gallus gallus domesticus) as predators of artificial prey, in order to determine whether the nutritional value of prey influences the degree to which predators discriminate between models and Batesian mimics. I found no direct evidence to support this hypothesis. When taken together, the results of my experiments highlight how much there is still to learn about mimicry as well as the need to test many of the hypotheses surrounding it.