Cleaning of coral reef fishes by the wrasse Labroides dimidiatus: Influence of client body size and phylogeny

Specialized cleaners remove ectoparasites from apparently cooperating coral reef fishes, This interaction may be a true mutualism, in which both participants benefit, or it may represent a case of exploitation by the cleaners of their clients' response to tactile stimulation. If clients benefit, it is predicted that clients with higher parasite load will seek cleaning more intensely than (and be preferred hy cleaners over) less parasitized clients, We tested for a relationship between client size, usually a reliable predictor of parasite load, and the frequency and duration of inspection by the cleaning wrasse Labroides dimidiatus, among 60 genera (132 species) of coral reef fishes on the Great Barrier Reef. Among species within genera, neither measures of client occurrence on regional reefs nor client size proved consistent predictors of cleaning rates. Using generic values as independent observations, both client size and client regional occurrence correlated positively with the duration and/or the frequency of inspection. However, these relationships disappeared when phylogenetically independent contrasts were used in the analysis, suggesting that the relationships were artifacts of phylogenetic effects. The strength of the associations between cleaners and clients varies among client genera independently of client size or commonness and may reflect the age and coevolutionary history of the different associations.