Client choice, competition, and cleaner dependence pressure cleaner fish to cooperate in mutualistic symbiosis
Mutualistic symbiosis is a finely tuned relationship between two species in which each receives a service that increases its own fitness in exchange for providing service to another. The evolutionary stability of such a relationship is dependent on all species performing in an honest manner. However, many species that participate in mutualistic symbiosis have been observed cheating, or taking benefits beyond those evolutionarily agreed upon. This study attempted to identify factors that contribute to the frequency of cheating at cleaning stations on coral reefs. In these relationships, small fish and crustaceans clean parasites from larger host organisms. Client abundance and proximity of cleaning stations were examined as indicators for competition between cleaners and client choice. These factors put pressure on cleaners to cooperate by creating competition for clients. It was found that there was a greater abundance of clients at stations where cheating occurred less frequently, suggesting that clients may have chosen those stations for the higher quality service demonstrated. Proximity of cleaning stations did not seem to influence the frequency of cheating. Finally, obligate cleaners spent more time cleaning individual clients and cheated less frequently than facultative cleaners, demonstrating their higher dependence on the relationship. Understanding the factors that motivate cleaners and clients to cooperate at cleaning stations is an important component to comprehending community dynamics on reefs, but it is not as clear of a relationship as is commonly described.