The four elements of within-group conflict in animal societies: an experimental test using the clown anemonefish, Amphiprion percula

Abstract

Conflicts of interest are part and parcel of living in a social group, yet actual conflict can be rare in established groups. Within limits, individuals can maximize the benefits of group living by resolving conflict with other group members. Thus, understanding what causes conflict, what determines its outcome, and how it is resolved holds the key to understanding the evolution and maintenance of sociality. Here, we investigate these questions using the clown anemonefish Amphiprion percula. Clownfish live in groups composed of a breeding pair and zero to four non-breeders that queue for breeding positions. Within groups, there is potential conflict over rank yet actual conflict is very rare. We staged contests in aquaria between pairs of nonbreeding individuals over access to a key resource (an anemone), analogous to contests that would occur at the onset of group formation in the wild. The initial size ratio between individuals tended to predict the intensity, and predicted the outcome and resolution of conflict: conflict intensity was greater when individuals were more similar in size; the probability of the smaller individual winning was greater when individuals were more similar in size; and the loser of the contest grew less than the winner when individuals were more similar in size. These results provide a critical test of foundational assumptions upon which our understanding of clownfish and other fish societies has been built. More generally, the results show that one of the simplest and most effective ways for animals to resolve conflict is to modify the phenotype that triggers conflict. causes conflict, what determines its outcome and how it is resolved holds the key to understanding the evolution and maintenance of sociality. Here, we investigate these questions using the clown anemonefish Amphiprion percula. Clownfish live in groups composed of a breeding pair and zero to four non-breeders that queue for breeding positions. Within groups, there is potential conflict over rank yet actual conflict is very rare. We staged contests in aquaria between pairs of non-breeding individuals over access to a key resource (an anemone), analogous to contests that would occur at the onset of group formation in the wild. The initial size ratio between individuals predicted the intensity, outcome and resolution of conflict: conflict intensity was greater when individuals were more similar in size; the probability of the smaller individual winning was greater when individuals were more similar in size; and the loser of the contest grew less than the winner when individuals were more similar in size. These results provide a critical test of foundational assumptions upon which our understanding of clownfish and other fish societies has been built. More generally, the results show that one of the simplest and most effective ways for animals to resolve conflict is to modify the phenotype that triggers conflict.

Lunar cycles of reproduction in the clown anemonefish Amphiprion percula: individual-level strategies and population-level patterns

“…Low anemone saturation occurs when resident individuals die, creating a vacancy in the anemone, but such mortality events are not temporally predictable. Following a mortality event, the first larva to settle will likely grow and gain a competitive advantage over other settlers enabling it to secure a spot in the anemone (Wong et al 2016). In light of this, natural selection will favor parents that produce larvae that settle at different times from the larvae of other parents, which means that natural selection will favor parents that lay their eggs at different times from other parents.…”

Finding Nemo’s Genes: A chromosome‐scale reference assembly of the genome of the orange clownfishAmphiprion percula

“…It is also one of the most important species for studying the ecology and evolution of coral reef fishes. The orange clownfish is used as a model species to study patterns and processes of social organization (Buston & Wong, 2014;Buston, Bogdanowicz, Wong, & Harrison, 2007;Wong, Uppaluri, Medina, Seymour, & Buston, 2016), sex change (Buston, 2003), mutualism (Schmiege, D'Aloia, & Buston, 2017), habitat selection (Dixson et al, 2008;Elliott & Mariscal, 2001;Scott & Dixson, 2016), lifespan (Buston & García, 2007) and predator-prey interactions (Dixson, 2012;Manassa, Dixson, McCormick, & Chivers, 2013). It has been central to ground-breaking research into the scale of larval dispersal and population connectivity in marine fishes (Almany et al, 2017;Pinsky et al, 2017;Planes, Jones, & Thorrold, 2009;Salles et al, 2016) and how this influences the efficacy of marine protected areas (Berumen et al, 2012;Planes et al, 2009).…”

Genetic relatedness in social groups of the emerald coral goby Paragobiodon xanthosoma creates potential for weak kin selection

“…The within‐group relatedness recorded here indicates that dominants may gain inclusive fitness by accepting nonbreeding group members as long as they remain small and inflict no costs. Both P. xanthosoma and A. percula subordinates are known to regulate their growth to remain under a size threshold to be tolerated in the group (Buston, 2003; Wong et al, 2007) and, at least in A. percula , subordinates that did this were found to inflict no fitness costs on dominants (Buston, 2004; Wong et al, 2016). In the absence of costs inflicted by the subordinates, the estimated within‐group relatedness of 0.025 may be high enough to confer kin‐selected benefits to the dominant breeders as their distant relatives go on to inherit their territories and breed when they die.…”