Meeting Abstract
Of all vertebrates, why fishes show the greatest diversity in spectral sensitivity remains an open question in the field of sensory ecology. Over the past several decades, rod and cone spectral sensitivity data have been amassed for hundreds of fish species, yet varying trends across clades make it difficult to identify the major factors influencing variation in this trait. Here, rod and cone λmax (photoreceptor class peak sensitivity) and chromacy (photoreceptor class number) values were compiled for a meta-analysis examining the ecological basis and functional significance of spectral sensitivity diversity in fishes. Examining rod sensitivity, linear models that correct for phylogenetic relatedness showed that rod λmax values, varying over just 64 nm, are best predicted by habitat and depth. A potential influence of environmental temperature was also identified, as fishes in temperate latitudes had longer wavelength rod λmax than those in the tropics. Examining patterns of cone spectral sensitivity showed that trichromacy was most common, ultraviolet λmax values were found exclusively in trichromacy and higher chromacy levels, and increasing chromacy, including from tetra- to pentachromacy, significantly increases sensitivity range. Using a recently developed method of multivariate phylogenetic latent liability modeling, depth, diet, body coloration, and body size of fishes were found correlate to chromacy level; however, after applying phylogenetic correction, the only remaining correlated predictor was depth. Together, this work shows ecological patterns of spectral sensitivity across ray-finned fishes, stressing the importance of considering phyletic heritage in studies of spectral sensitivity and suggesting that selection can act on even the smallest differences in sensory ability.
