Paternity, sex roles and fish: Who cares?

Author(s): Kahn AT, Schwanz LE, Kokko H

Summary:

Female parental care predominates in most taxa because sperm competition and paternity uncertainty hamper the evolution of male care. What if fathers can, however, increase their share of paternity by providing parental care? Here we show that this provides an important modification to Dawkins and Carlisle’s (1976) cruel bind – the idea that whichever parent releases their gametes first can desert the other, who is left ‘holding the baby’. In our model, post-mating protection of paternity provides an extra incentive for males to stay with their young after gamete release. If offspring survive better when guarded, this paternity protection is enough to kick-start the evolution of male-only parental care from a no-care scenario. Our results help to explain the evolution of parental sex roles in fish, where male-only care (the norm) is associated with external fertilization, whilst female-only care almost always evolves after an initial transition to internal fertilization.

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