Sex change as a survival strategy

Sequential hermaphroditism (sex change) is understood to be a strategy that maximizes lifetime reproduction in systems where one sex confers highest fitness early in life, and the other later in life. This strategy is evolutionarily stable despite costs to growth, survival, or current reproduction. Few studies have examined advantages of sex change outside of reproduction. The mangrove rivulus fish, Kryptolebias marmoratus, presents a unique system in which to study non-reproductive consequences of sex change because reproductive opportunity decreases significantly with sex change. In natural conditions, individuals develop as self-fertilizing simultaneous hermaphrodites. Some individuals change sex to male at various points after sexual maturity, even in isolation, essentially foregoing future reproductive assurance. In a large-scale experiment that examined fitness differences among individuals exposed to ecologically relevant environmental challenges, we found that individuals that change sex from hermaphrodite to male had overwhelmingly greater chances of survival compared to those that remained hermaphrodite. Furthermore, hermaphrodites derived from lineages with higher propensities to change sex experienced greater survival advantages by changing sex. Our results indicate that sex change may be a survival strategy, one with genotype-dependent consequences.