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

Abstract

In many hierarchical animal societies, dominant individuals control group membership owing to their power to evict subordinates. In such groups, the presence of subordinates, and therefore group stability, is continually dependent on subordinates being tolerated by dominants. The dominant decision to tolerate or evict is, in turn, dependent on the costs and benefits to dominants of subordinate presence. We investigated the effect of subordinate presence on dominants in the female dominance hierarchy of the dwarf angelfish Centropyge bicolor, using both observations of natural groups and experimental removals of subordinates. We found that the presence of subordinates had no effect on dominant access to resources, as measured by dominant foraging rates and home range areas, nor on dominant fitness, as measured by growth rates and spawning frequencies. Our results suggest that the presence of subordinates has a neutral effect on the current fitness of dominants, so that dominants have no great incentive to evict subordinates. We discuss the possibility that tolerance of subordinates might be further explained by considering future fitness, as dominant females in these haremic protogynous angelfish stand to inherit the male position, whereupon subordinate females change from potential competition to useful mates.

Repeated cyclone events reveal potential causes of sociality in coral-dwelling Gobiodon fishes

“…This may indicate that GF species of gobies will tolerate greater coral saturation (i.e. more subordinates in smaller corals) following a disturbance, especially if they benefit in future reproduction or survival from doing so [ 79 ].…”

“…This may be due to social conflict [ 6 ] and recruitment prevention [ 37 ], demonstrated in other social fishes at high rates of habitat saturation. Smaller group sizes suggest lower numbers of subordinates which may have a negative impact on future reproductive efforts [ 79 ]. Smaller group sizes could also be problematic under a regime of repeated disturbance as larger group size may provide a level of redundancy and buffer effects of future disturbance [ 26 , 42 , 43 ].…”