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Aim: Several drivers explain the global distribution of all reef fish. However, whether these drivers also explain the distribution and traits of a functional subgroup involving cleaner fishes remain unclear. Here we examine the variation in traits of cleaner fishes and test whether historical, environmental, ecological and geographical drivers are correlated with cleaner species richness and abundance at global reefs. Location: Tropical and subtropical reefs. Taxon: Actinopterygii. Methods: We tested whether species traits and trait space vary between facultative (i.e. species that clean only during the juvenile stages or sporadically) and dedicated (i.e. species that clean during their whole lives) cleaner types. We compiled data from local checklists (relative richness) and belt transects (standardized richness and abundance). We built four models to test whether past and current isolation (i.e. distance from Quaternary refugia and biodiversity centres), sea temperature, primary productivity, local species pool and abundance of potential clients influenced the relative richness and abundance of cleaners. Results: Facultative cleaners had high trait variability that contributed disproportionally to the trait space, whereas dedicated cleaners exhibited low trait variability. Cleaner species richness was higher in the Indo‐Pacific and Caribbean provinces, but the relative richness and standardized abundance of cleaners were higher in the Atlantic (i.e. North Eastern and Southwestern) and Eastern Pacific. Isolation influenced the relative richness of facultative cleaners, whereas the distance to Quaternary refugia, sea temperature and isolation influenced the relative richness of dedicated cleaners. Local species richness and standardized abundance of cleaner fish exhibited a strong relationship with regional diversity. The standardized abundance of both facultative and dedicated cleaners was influenced by the abundance of potential clients and the local species pool. Main conclusions: The small trait space occupied by cleaner fishes may reflect their restricted origin among lineages of reef fishes. Differences in the relative richness and standardized abundance of cleaner fishes across marine realms suggest a strong influence on biogeographical history. Our results also indicate that cleaner fishes originated mostly in peripheral areas in high latitudes due to the absence of dedicated cleaners. Our results imply that cleaner fishes do not follow the pattern of main centres of origin described for reef fishes due to opportunistic cleaning behaviour that originated with higher frequency at locations with low species richness. [ABSTRACT FROM AUTHOR]

Cleaning behavior is a well-known example of trophic specialization that is widespread in marine organisms from both tropical and temperate ecosystems. Cleaner species can be more or less specialized in different aspects of cleaning interactions, and it is often assumed that the more specialized cleaners are, the more they rely on clients for food. However, cleaners can consume different items in different sites, and the factors influencing such variation are still poorly understood. Here, we investigated the diet and distribution of the barber goby Elacatinus figaro across marginal reefs of the Brazilian coast. We evaluated E. figaro's reliance on cleaning interactions for food and asked whether its diet and abundance corresponded to the availability of ectoparasites and/or clients. The diet of E. figaro varied across sites, but ectoparasite reliance was similar and did not correspond to client's infestation loads. Moreover, the density of E. figaro did not correlate with the density or richness of potential clients. These support the hypothesis that E. figaro is less reliant on cleaning interactions for food than other cleaning goby species and suggest a high feeding and behavioral plasticity in marginal reefs. This study also highlights that the current dichotomous classification scheme of dedicated versus facultative cleaners fails to capture the subtle nuances of cleaning behavior and should therefore be used with caution in future comparative studies. [ABSTRACT FROM AUTHOR]