Benefits and Costs of Dominance in the Angelfish Centropyge bicolor

Abstract

Social groups are often structured by dominance hierarchies in which subordinates consistently defer to dominants. High‐ranking individuals benefit by gaining inequitable access to resources, and often achieve higher reproductive success; but may also suffer costs associated with maintaining dominance. We used a large‐scale field study to investigate the benefits and costs of dominance in the angelfish Centropyge bicolor, a sequential hermaphrodite. Each haremic group contains a single linear body size‐based hierarchy with the male being most dominant, followed by several females in descending size order. Compared to their subordinate females, dominant males clearly benefited from disproportionately high spawning frequencies, but bore costs in lower foraging rates and greater aggressive defence of their large territories. Within the female hierarchy, more dominant individuals benefited from higher spawning frequencies and larger home ranges, but displayed neither higher foraging rates nor spawn order priority. However, dominance in females was also linked to aggressiveness, particularly towards immediate subordinates, suggesting that females were using energetically costly aggression to maintain their high rank. We further showed by experimentally removing dominant females that the linear hierarchy was also a social queue, with subordinates growing to inherit higher rank with its attendant benefits and costs when dominants disappeared. We suggest that in C. bicolor, the primary benefit of high rank is increased reproductive success in terms of current spawning frequency and the prospect of inheriting the male position in the near future, which may be traded off against the cost of aggressively defending rank and territory.

Male immigration triggers increased growth in subordinate female meerkats

“…Our results reinforce previous evidence of the effects of changes in social conditions on growth in social mammals (Huchard et al, ). Effects of social conditions on growth have been documented in a number of fish where growth commonly persists throughout the lifespan (Ang & Manica, ; Buston, ; Wong et al, ) but are uncommon in mammals which commonly show relatively little growth after individuals reach adulthood (Bennett, Jarvis, Aguilar, & McDaid, ; Karkach, ; Zullinger, Ricklefs, Redford, & Mace, ). However, a number of recent studies now show that the transition from non‐breeding to breeding status is associated with a renewal of growth in either or both sexes (Emery Thompson et al, ; O'Riain, Jarvis, et al, ; Young & Bennett, ) and these effects may be less rare than has been supposed.…”

“…In these areas, subordinate females might gain by investing acquired energy into fat reserves rather than into muscle or bones in order to increase their probability to survive the next drought. Alternatively, increases in rates of growth may have deferred costs to rates of aging and survival (Metcalfe & Monaghan, 2001, 2003 or may lead to increased rates of aggression from other group members (Ang & Manica, 2010;Buston, 2003;Wong, Buston, Munday, & Jones, 2007;Wong et al, 2008).…”

“…Recent research on social vertebrates shows that individuals of some species adjust their growth rate in relation to variation in the costs and benefits of body mass generated by changes in their social environment. In some group‐living fish, subordinates whose mass approaches that of rank neighbors immediately above them in social hierarchies reduce their growth rate to avoid becoming the target of persistent aggression (Ang & Manica, ; Buston, ; Heg, Bender, & Hamilton, ; Wong, Munday, Buston, & Jones, ). In some polygynous mammals, males increase growth rates leading to in overall mass and in the development of secondary sexual characters when they acquire their own breeding territory (Clutton‐Brock, ; Emery Thompson, Zhou, & Knott, ; Oliveira, Canário, & Ros, ; Setchell, ) or when their social status changes.…”

The influence of status and the social environment on energy stores in a social fish

“…Subordinate individuals often grow more slowly than dominants, due to a variety of mechanisms including reduced food accessibility (Fausch, 1984;Sloman et al, 2000) and increased physiological stress resulting from aggression by more dominant individuals (Gilmour et al, 2005). Subordinates in several species with size-based dominance hierarchies have decreased somatic growth, which may reduce rank-related conflict with other individuals in their group [Neolamprologus pulcher (Trewavas & Poll 1952): Heg et al, 2004;Hamilton et al, 2005;Hamilton & Heg, 2008; Amphiprion percula (Lacépède 1802): Buston, 2003; Amphiprion ocellaris Cuvier 1830: Mitchell & Dill, 2005; Paragobiodon xanthosoma (Bleeker 1853): Wong et al, 2007; Centropyge bicolor (Bloch 1787): Ang & Manica, 2010]. Subordinates may also suppress their reproduction to minimize reproductive conflict with dominant individuals (Bell et al, 2014).…”

Effect of the Presence of Subordinates on Dominant Female Behaviour and Fitness in Hierarchies of the Dwarf Angelfish Centropyge bicolor

“…Although low-ranking subordinates in C. bicolor groups may not gain much current reproduction, they benefit from remaining within the group owing to the prospect of inheritance of dominance and its attendant reproductive benefits (Ang & Manica 2010b). On the other hand, dominant females gain no obvious benefit from the presence of subordinate females, as these fish are not cooperative breeders and individuals forage and take shelter from predators individually.…”