Behavioral syndromes and the evolution of correlated behavior in zebrafish

Studies of “behavioral syndromes” in different populations and species of animals can be used to shed light on the underlying mechanisms of evolution. For example, some personality syndromes suggest the existence of an underlying hormonal link, whereas other relationships between boldness and aggression appear to be the result of similar selective pressures. Here, we used 1 wild-derived and 2 laboratory strains of zebrafish (Danio rerio) to examine relationships among 5 behavioral measures: shoaling, activity level, predator approaches, latency to feed after a disturbance, and biting to a mirror stimulus. We found evidence of an activity syndrome, as if underlying metabolic costs influence variation in multiple forms of behavior. Evidence for a relationship between boldness and aggression was also apparent but depended both on strain and which specific behavior patterns were identified as measures of “boldness.” Although some comparisons of laboratory and wild-derived strains were consistent with a domestication syndrome, others were not. Most observed relationships were relatively weak and occasionally inconsistent, arguing against strong underlying genetic linkages or pleiotropic effects relating any of the behavioral measures. Instead, it may be more important to study the details of selective context or the long-term impact of linkages between some, but not all, of a large set of genes influencing complex behavioral traits. We found profound differences among strains in most behavior patterns, but few sex differences. One strain (TM1) was consistently different from the others (SH and Nadia) being more social, more likely to approach predators, and taking less time to recover from disturbance than were the other 2 strains.