Dynamic adjustment of parental care in response to perceived paternity.

Theories of parental care evolution predict that genetic relatedness will be an important variable in the amount of care a parent provides. However, current inferences of relatedness-based parental investment from studies in humans and birds remain challenged. No study has yet demonstrated parental care adjustment in a manner uncomplicated by life-history correlates or experimental design. We now present a unique test that controls for individual life histories and demonstrates paternity-related dynamic adjustments in parental care. Brood-rearing male bluegill sunfish (Lepomis macrochirus) that are cuckolded to a varying degree will either increase or decrease their parental investment in response to changing information on paternity during brood development. Specifically, as parental males detect paternity lost to cuckolders and, hence, a reduction in the value of their brood, they adaptively lower their level of parental care. Conversely, if they detect that their paternity is higher than previously assessed, they adaptively raise their level of parental care. This dynamic adjustment during brood rearing indicates the importance of genetic relatedness in parental investment decisions and provides needed empirical support for theoretical predictions.