Like drivers at a carwash, coral reef fish queue at cleaning stations to have parasites, slime, and broken scales nibbled away by smaller fish and by shrimps. These species interactions are interesting for their tropical ubiquity and the diversity of species that can be found as clients and cleaners. Although some cleaners are obligate professionals, others are dilettantes and adopt this life-style intermittently.
Floeter et al. have compiled data from around the tropics to tease out the selection pressures acting on these interactions. The basic emerging relationship is that, owing to abundance, the more common, planktivorous, and gregarious species take up most of the cleaner's time. Client size doesn't seem to be very important, nor does professionalism, when it comes to dealing with carnivores that might eat the fish or shrimp that is cleaning them. Hence, this study adds to a growing body of evidence suggesting a central role for abundance in structuring species interactions. Guimarães et al. have also looked at cleaning mutualisms. They document a pattern of nestedness, dominated by a core of a few, very busy cleaner species that service a wide variety of clients, with less popular cleaners and clients, both of which interact with core species but not each other, lounging on the periphery. -- CA
J. Anim. Ecol. 10.1111/j.1365-2656.2006.01178x (2006); Biol. Lett. 10.1098/rsbl.2006.0562 (2006).
