Figure 1.

The male territorial phenotype in the round goby. (a). Usually, round goby males (and females) are light brown or grey. In the spawning season, territorial males develop a black coloration. (b). The territorial phenotype may be predetermined by early life conditions such as predation or food availability. If this predetermination is mediated by DNA methylation (DNAme), characteristic patterns should precede the appearance of the external phenotype. (c). Alternatively, the territorial phenotype may be induced by current conditions such as nest availability. In a condition-dependent scenario, characteristic DNAme patterns should arise concomitantly with the phenotype. Black and grey areas represent methylated and unmethylated regions in the genome.