Abstract
Colour change in animals can be adaptive phenotypic plasticity in heterogeneous environments. Camouflage through background colour matching has been considered a primary force that drives the evolution of colour changing ability. However, the mechanism to which animals change their colour and patterns under visually heterogeneous backgrounds (i.e. consisting of more than one colour) has only been identified in limited taxa. Here, we investigated the colour change process of the Japanese tree frog (Hyla japonica) against patterned backgrounds and elucidated how the expression of dorsal patterns changes against various achromatic/chromatic backgrounds with/without patterns. Our main findings are i) frogs primarily responded to the achromatic differences in background, ii) their contrasting dorsal patterns were conditionally expressed dependent on the brightness of backgrounds, iii) against mixed coloured background, frogs adopted intermediate forms between two colours. Using predator (avian and snake) vision models, we determined that colour differences against different backgrounds yielded perceptible changes in dorsal colours. We also found substantial individual variation in colour changing ability and the levels of dorsal pattern expression between individuals. We discuss the possibility of correlational selection on colour changing ability and resting behaviour that maintains the high variation in colour changing ability within population.
Highlights
IntroductionColour changing animals are able to change their colours or patterns to enhance the degree of camouflage (e.g. background colour matching or disruptive pattern expression) against their background[24,25]
Colour changing animals are able to change their colours or patterns to enhance the degree of camouflage against their background[24,25]
This simultaneous change is pronounced in tree frogs since the dorsal pattern expression varies from complete disappearance to highly contrasting patterns within individuals
Summary
Colour changing animals are able to change their colours or patterns to enhance the degree of camouflage (e.g. background colour matching or disruptive pattern expression) against their background[24,25]. The evidence of camouflage in terms of both achromatic and chromatic colour matching are present[21,26,27] It has rarely been tested how animals change their colours under the conditions of mixed-colour backgrounds which can be found in many natural substrates (but see Kats and van Dragt[23]). It is crucial to examine how frog colour changes at night when the light intensity and exposure decreases dramatically Some animals, such as cuttlefish, can actively modulate their body colours through visual perception of the background[24], but it has rarely been demonstrated in other taxa (including anurans as far as we know) whether the animal’s visual perception of environments plays role in colour change processes. We tested whether colour change on mixed coloured backgrounds was an intermediate body colour or matched with one of the background colours
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