![]() ![]() Intimidation hypothesisīlest’s pioneer work demonstrating the role of eyespots in reducing predation paved the way for further intensive studies establishing that eyespots can indeed intimidate predators. The current study focusses on the intimidation effects of large, conspicuous eyespots, and addresses how predator perception influences eyespot evolution. There is experimental evidence supporting both hypotheses (intimidation hypothesis deflection hypothesis ). Large, conspicuous eyespots are considered to be intimidating for the predator thereby decreasing the chances of attack – the “Intimidation Hypothesis”, whereas smaller eyespots closer to the wing margin are thought to attract attention toward themselves thus deflecting predatory attacks away from the more vital parts of the prey – the “Deflection Hypothesis”. Two broad hypotheses explain how eyespots may be effective against predation. However, the most widespread selective agent shaping the evolution of eyespot is, arguably, predation pressure. Eyespots are also implicated as signals in the context of male-male competition in fish. anynana are used as signals in assessing the quality of mates by both males and females. Investigations have shown that eyespots in B. Experimental studies have directly demonstrated the wide range of selective forces that are likely to have shaped the myriad eyespots currently found in nature. Comparative studies within a phylogenetic framework have shed light on the patterns of evolution of eyespots and furthered our understanding of the evolutionary forces that may have shaped the multitude of eyespots. Major strides have been taken toward understanding the genetics and developmental processes involved in eyespot formation in butterflies, particularly through studies on laboratory populations of Bicyclus anynana. Lepidopteran insects have been especially popular for investigations into eyespot evolution. ![]() Although occasional studies were carried out since the early 1900s, the last few years have culminated in a range of novel studies, which have significantly furthered our understanding of the evolution of these intriguing structures, and eyespots have become a very exciting model system in evolutionary and developmental biology. ![]() These include evo-devo, behavioral, phylogenetic and theoretical studies. Biologists have long been fascinated by these eyespots and multiples lines of investigation have addressed the question of how and why eyespots have evolved in different groups of organisms. They exhibit enormous diversity in morphology, occurring in an array of sizes and colour combinations, from very simple to highly complex structures. They are widely found in insect groups, especially butterflies and moths, as well as in vertebrates such as fish, birds and frogs. We discuss the implications of our results for the understanding of eyespot evolution.Įyespots - conspicuous, circular or quasi-circular colour markings – are remarkably common morphological features in the animal kingdom. The study highlights the importance of pairedness of eyespots, and supports the hypothesis that two is a biologically significant number that is important in prey–predator signalling. However, across all experiments, models with a pair of patterns, symmetric or asymmetric, eyelike or non-eye-like, suffered from fewer attacks compared with other models. Furthermore, we did not find a significant effect of symmetry of patterns, again in discordance with previous work. Non-eye-like, fan shaped patterns derived from eyespots were found to be just as effective as eye-like circular patterns. However, contrary to previous, outdoor experiments, we found that the total area of eyespots did not affect their effectiveness. We first established that birds avoided models with a pair of eyespots. We conducted choice tests where artificial paper models mimicking Junonia almana butterflies were presented to chickens and their preference of attack recorded. We undertook a series of indoor experiments to understand the relative importance of conspicuousness and eye-mimicry, and therefore how predator perception may have influenced the evolution of eyespots. There is an on-going debate about which of these better explains the effectiveness of eyespots against predation. Two competing hypotheses seek to explain the cause of intimidation, one suggesting ‘eye-mimicry’ and the other their ‘conspicuousness’ as the reason. Work over the last decade has shown that a major function of eyespots is their ability to reduce predation by being intimidating to attacking predators. Many butterflies possess striking structures called eyespots on their wings, and several studies have sought to understand the selective forces that have shaped their evolution. ![]()
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