To clean or not to clean: Cleaning mutualism breakdown in a tidal environment

Abstract

The dynamics and prevalence of mutualistic interactions, which are responsible for the maintenance and structuring of all ecological communities, are vulnerable to changes in abiotic and biotic environmental conditions. Mutualistic outcomes can quickly shift from cooperation to conflict, but it unclear how resilient and stable mutualistic outcomes are to more variable conditions. Tidally controlled coral atoll lagoons that experience extreme diurnal environmental shifts thus provide a model from which to test plasticity in mutualistic behavior of dedicated (formerly obligate) cleaner fish, which acquire all their food resources through client interactions. Here, we investigated cleaning patterns of a model cleaner fish species, the bluestreak wrasse (Labroides dimidiatus), in an isolated tidal lagoon on the Great Barrier Reef. Under tidally restricted conditions, uniquely both adults and juveniles were part‐time facultative cleaners, pecking on Isopora palifera coral. The mutualism was not completely abandoned, with adults also wandering across the reef in search of clients, rather than waiting at fixed site cleaning stations, a behavior not yet observed at any other reef. Contrary to well‐established patterns for this cleaner, juveniles appeared to exploit the system, by biting (“cheating”) their clients more frequently than adults. We show for the first time, that within this variable tidal environment, where mutualistic cleaning might not represent a stable food source, the prevalence and dynamics of this mutualism may be breaking down (through increased cheating and partial abandonment). Environmental variability could thus reduce the pervasiveness of mutualisms within our ecosystems, ultimately reducing the stability of the system.

Guides and cheats: producer–scrounger dynamics in the human–honeyguide mutualism

“…Human–honeyguide cooperation is similarly robust to exploitation by heterospecific wax-eating species [32], and our results are in-line with studies indicating that several other mutualisms are similarly robust to exploitation or cheating. For example, nectar-robbing insects do not disrupt plant-pollinator mutualisms [60] and cleaning mutualisms are not threatened by cleaner-fish that eat their client's tissue rather than removing ecto-parasites [61] (but see [62]). As such, our results add to growing evidence that the threat exploiter or scrounger individuals pose to the persistence of mutualisms appears to be substantially smaller than previously suggested [63,64].…”

A marine cleaning mutualism provides new insights in biological market dynamics

“…First, there are several recent key new insights (e.g. [21,[38][39][40][41][42]) that have not been used in reviews but affect our thinking on BMT. In one paper, a reduction in cleaner densities did not lead to predicted changes in service quality [21].…”

Sociality and self-awareness in animals

“…However, like other species with possible self-awareness, the cleaner wrasse is very social. Cleaning stations, where other fish can go to be cleaned by the cleaner wrasse, are typically composed of either a pair of adults, a group of juveniles, or a group of females and one dominant male (Dunkley et al, 2020). As such, the cleaner wrasse frequently interacts with conspecifics.…”