Evol Ecol Res 5: 89-104 (2003)     Full PDF if your library subscribes.

Social correlates of reproductive success in false clown anemonefish: subordinate group members do not pay-to-stay

Jeremy S. Mitchell*

Behavioural Ecology Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada

e-mail: jmitchel@sfu.ca


In group-territorial species, subordinate group members may affect the reproductive success of a dominant, breeding pair. Dominants should be choosy, evicting subordinates whose presence does not increase reproductive success in favour of those whose presence is beneficial. I examined correlations between components of reproductive success and measures of social group composition in false clown anemonefish (Amphiprion ocellaris), in which breeding pairs tolerate subordinates that could be expelled from sea anemone hosts. Statistical interactions between group members’ lengths, including interactions with the length of a non-breeding subordinate, were significantly better predictors of clutch size than a female’s absolute length. For large females, clutch size increased with the length of the largest subordinate. The relationship between laying frequency and group composition was similar to that of clutch size, except that the statistical interaction was between subordinate and male, not female, length. Hatching success was not correlated with female length or with the length of the largest subordinate. Hatching success was correlated with the interaction between male length and the total number of subordinates; on average, hatching success declined as group size increased but the effect direction reversed at larger male lengths. Because clutch size and laying frequency were not correlated with a subordinate’s size directly, but rather with interactions among group members’ lengths, and because hatching success on average declined with group size, I conclude that the presence of subordinates did not have a positive effect on a breeding pair’s reproductive success – that is, there is no evidence that subordinate false clown anemonefish pay-to-stay. This result is surprising given the ease with which a breeding anemonefish pair can evict non-beneficial subordinates.

Keywords: Amphiprion, cooperative breeding, queue, reproductive success, social organization.

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