Microhabitat use and body size drive the evolution of colour patterns in snapping shrimps (Decapoda: Alpheidae: Alpheus)

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AbstractBackground matching and disruptive coloration are common strategies used by animals to increase concealment, whereas motion-dazzle may prevent capture after recognition. Studies have related background matching to habitat dependency and survival success, whereas for animals with highly contrasting patterns it has been shown that they are able to explore a broader range of habitats due to disruptive coloration, and possibly via motion-dazzle. However, the effects of these strategies are likely to be influenced by body size and to work better for smaller species. We applied phylogenetic comparative methods to test the hypothesis that smaller snapping shrimps (genus Alpheus) with high-contrast stripes would be able to utilize more microhabitats than non-striped and larger species. We used a published phylogeny of the American species of Alpheus, studies that have described alpheid microhabitats and size, and high-resolution photographs of each species in the phylogeny. Our categorical analysis suggested that generalist snapping shrimps are more likely to have stripes than specialist shrimps, and this effect was stronger in smaller species. Similarly, we found an interacting effect of body size and habitat use on the degree of luminance contrast: smaller generalist species had higher contrast values than average-sized and habitat-specialist species. Therefore, predators, body size and frequency of microhabitats are likely to have influenced the evolution of colour patterns in Alpheus.