Abstract and Summary
Brook charr (Salvelinus fontinalis) defend territories and show high levels of agonistic behaviour. In contrast, lake charr (S. namaycush) are non-territorial and rarely show any agonistic behaviour. The genetic determinance of behavioural differences between these species was confirmed by the behavioural similarity of brook charr backcross hybrids and brook charr and a significant maternal effect on hybrid behavioural phenotypes.
Backcross and F2 generations showed either one of two distinct behavioural strategies, one aggressive and territorial and the other non-aggressive and non-territorial. It seems most likely that these strategies are conditional on individual phenotypes, such as size of nearby conspecifics. However, precise measurements of costs and benefits of each strategy are required to distinguish between these alternate hypotheses for either species.
Each action pattern was an independent pattern of variation and a distinct behavioural unit. However, patterns were coordinated with all other patterns at a higher hierarchical level (corresponding to the particular behavioural strategy). It seems most likely that these strategies would be controlled by a polygenic system, even though the nature of our data does not allow us to make firm conclusions in this regard.