Evolved bet-hedging through maternal effects: developmental trajectory variation in annual killifish across a wet–dry cycle

Abstract

For annual killifishes in temporary wetlands, diapause induction during embryonic development is considered a bet-hedging strategy to endure unpredictable dry periods. However, the extent to which killifish embryos exhibit developmental variation—and the underlying drivers—remains unclear. We assessed diapause induction patterns of the endangered killifish Matilebias cyaneus across three hydrological phases (early-wet, drying, late-wet) of a temporary wetland. Wild egg clutches with known parentage were incubated under common-garden conditions to monitor entry or skipping of early and mid-embryonic diapause (diapause I and II). Most embryos skipped both diapauses in the early-wet phase, while mixed trajectories were observed in drying and late-wet phases. Interestingly, this variation may reflect not only environmental phase alignment but also maternal age-related epigenetic effects, which have been shown to influence diapause regulation in annual killifishes. These findings support the idea that fine-tuned bet-hedging strategies may evolve through natural selection acting on maternal programming mechanisms, rather than on direct embryo sensing of hydrological conditions. Understanding survival strategies of wetland taxa across seasonal gradients remains key to predicting species resilience under climate-driven hydroperiod shifts.