Background color matching affects sexual behavior, growth, and mortality rate in an African cichlid

Phenotypic plasticity allows organisms to adapt to changing environments within their lifetimes. However, environmentally induced changes in the plastic trait of interest may influence a range of fitness-related traits due to trade-offs, pleiotropy, linkage, or epistasis of genes regulating the plastic trait. These correlated responses may constrain or facilitate the evolution of plasticity, but their evolutionary implications are often poorly understood due to a lack of data on their direction and magnitude. Males in the African cichlid <i>Astatotilapia burtoni</i> are blue or yellow, and males are able to adjust their body coloration to the color of the background, presumably to increase crypsis. To test whether background color influences fitness-related traits, we raised mix-sex groups of juvenile <i>A. burtoni</i> to adulthood in yellow or blue tanks. We found that more males adopted the blue phenotype in blue tanks while more males adopted the yellow phenotype in the yellow tank, though the degree of background color matching decreased with age. Males, but not females, from blue tanks showed earlier sexual maturation than those held in yellow tanks. However, across the duration of the experiment, there was a higher occurrence of breeding in females housed in yellow tanks than those that were housed in blue tanks. In addition, fish in blue tanks exhibited reduced growth rate but higher survivorship relative to their yellow-reared counterparts. Our data suggest that background color affects important fitness-related traits in a color polymorphic cichlid, which may influence the evolution of phenotypic plasticity.