Sexual signal design is an evolutionary puzzle that has been partially solved by the hypothesis of sensory drive. Framed in signal detection theory, sensory drive posits that the attractiveness of a signal depends on its detectability, measured as contrast with the background. Yet, cognitive scientists have shown that humans prefer images that match the spatial statistics of natural scenes. The explanation is framed in information theory, whereby attractiveness is determined by the efficiency of information processing. Here, we apply this framework to animals, using Fourier analysis to compare the spatial statistics of body patterning in ten species of darters (Etheostoma spp.) with those of their respective habitats. We find a significant correlation between the spatial statistics of darter patterns and those of their habitats for males, but not for females. Our results support a sensory drive hypothesis that recognizes efficient information processing as a driving force in signal evolution.

Understanding the causes and risks of pathogen host-shifts remains one of the most important challenges in disease ecology (Borremans et al., 2019). Host-shifts occur when a pathogen is spread from an ancestral host to a new host species in which it shares no coevolutionary history. The importance of host-shift pathogens is clear for their hosts: a meta-analysis examining the evolutionary history of host-pathogen associations across all taxa found evidence of historic host-shifts in 93% of studies (Vienne et al., 2013). While much

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13The diversity of animal visual displays has intrigued scientists for centuries. Sexual selection theory has 14 explained some of this diversity, yet most of this effort has focused on simple aspects of signal design, 15 such as color. The evolution of complex patterns that characterize many sexual displays remains largely 16unexplained. The field of empirical aesthetics, a subdiscipline of cognitive psychology, has shown that 17humans are attracted to visual images that match the spatial statistics of natural scenes. We investigated 18whether applying this result to animals could help explain the diversification of complex sexual signaling 19 patterns. We used Fourier analysis to compare the spatial statistics of body patterning in ten species of 20 darters (Etheostoma spp.), a group of freshwater fishes with striking male visual displays, with those of 21 their respective habitats. We found a significant correlation between the spatial statistics of darter patterns 22and those of their habitats for males, but not for females. Our results suggest that visual characteristics 23 of natural environments can influence the evolution of complex patterns in sexual signals. 24 25

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