The evolution of cleaning mutualism and predator cooperation in a radiation of Caribbean fishes

The steps by which neutral, random and/or negative biological interactions evolve into mutualistic ones remain poorly understood. Here, we study Elacatinus gobies and the fishes from which they clean parasites, termed 'clients'. Colorful stripes are common to mutualist cleaners and non-cleaning sister species. Blue stripes are unique to obligate cleaners. We quantified the contrast potential of ancestral and novel stripe colors, using fish color vision models, and determined that color stripes have become more visible to clients over evolutionary time. In turn, we focused on the role of color as a potentially specialized signal. We show that cleaners possess a putative chemical defense (one multimedia file in .mov format included) and demonstrate that stripes are sufficient to elicit client stereotypical posing behavior and to deter attack. Analysis of previously published records show that yellow cleaners tend to predators less than expected, compared to green and blue cleaners. Our results highlight evolution from predator avoidance to tolerance with conspicuous advertising reinforced by chemical defense in cleaners. Similar trajectories, via recognizable signals to risky partners, may be common in other diffuse mutualisms. We discuss the generality of defense and signal traits in other species rich lineages of mutualists.Ph.D.Committee Chair: Streelman, J. Todd; Committee Member: Ferraro, Paul; Committee Member: Goodisman, Michael; Committee Member: Hay, Mark; Committee Member: Walker, L. DeEtt