Abstract
No evolutionary explanation for the striking colouration of coral reef fish has been established to date. Here I present the "Hyper-Visible World" hypothesis, which proposes that coral reef habitats impose special conditions on the evolution of body-colour communication for mobile fish - that is, fish that roam across coral reef formations. The special conditions are: 1) the high clarity of water during daylight hours, and 2) the unpredictable pattern/ visual complexity of the coral habitat itself. The hypothesis suggests that, in a signal transmission framework, the visual exposure (signal) of mobile fish cannot be effectively reduced so as to make a difference to predator-prey interactions. This negates the possibility of effective colour-based camouflage. In contrast, the selective pressures that usually come secondary to camouflage (such as sexual, aposematic or territorial display) benefit from these same conditions, driving the evolution of the colour patterns in this environment - the conspicuousness and dazzling colour diversity that we commonly associate with coral reef fish.
Highlights
Being able to hide in plain sight is a major selective pressure for both prey and predator species[1,2]
It is in this context that the dazzling colouration of fish inhabiting coral reefs and other tropical bodies of water has puzzled scientists since the formulation of natural selection theory[3,4,5,6,7,8,9]
Alfred Russel Wallace, co-proponent of the natural selection theory, put forward a hypothesis that relied instead on the existence of a camouflage purpose of those colours and patterns, whereby “brilliantlycoloured fishes from warm seas are many of them well concealed when surrounded by the brilliant sea-weeds, corals, sea-anemones, and other marine animals, which make the sea-bottom sometimes resemble a fantastic flower-garden”[3]
Summary
Being able to hide in plain sight is a major selective pressure for both prey and predator species[1,2]. Traits increasing the ability of individuals to camouflage in the environment have likely been under strong selection since vision emerged, having guided to a great extent the evolution of visual displays in the animal world It is in this context that the dazzling colouration of fish inhabiting coral reefs and other tropical bodies of water has puzzled scientists since the formulation of natural selection theory[3,4,5,6,7,8,9]. Signalling in high visual resolution can promote the genesis of new species through sensory-drive[12,16], a process whereby subtle changes in either colour patterns or in sensory/cognitive biases for attraction to those patterns can lead to the reproductive isolation of part of a population In this sense, the high resolution of signals coupled with the high productivity of coral reefs might account for the high rates of sympatric speciation observed in these habitats. Grant information The author(s) declared that no grants were involved in supporting this work
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