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RESEARCH PRODUCT

Bet-hedging in diapausing egg hatching of temporary rotifer populations - A review of models and new insights

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Habitat unpredictability is a local adaptation factor shaping life-history traits in rotifer populations. It may select for the evolution of bet-hedging through risk-spreading strategies in diapausing egg hatching. This means that a fraction of diapausing eggs in wild populations do not hatch even when the conditions are favorable for population growth. Thus, there is a remaining fraction of viable diapausing eggs standing in the sediments for longer periods. According to theory, it is expected that the incidence of bet-hedging strategies for diapausing egg hatching will be higher in more uncertain habitats. Here, we review the major predictions derived from theoretical models applied to the case of monogonont rotifers. In the simplest “bad versus good season” models, the highest environmental uncertainty occurs when the probability of a good season is 0.5, and then the optimal hatching fraction is 0.5 too, implying maximum variance in hatching (i.e., maximum bet-hedging). However, there is still little evidence to support this prediction. This is most likely due to the lack of long-term data of habitat fluctuations and the difficulties in identifying and analyzing bet-hedging strategies, as well as the potential to confound genetic variation and phenotypic plasticity. Moreover, we provide new evidence supporting the occurrence of bet-hedging strategies associated with diapausingegghatchingin theBrachionus plicatilisspecies complex. Ouranalysessuggesta gradient of predictability in the habitats of these rotifers, and the existence of a significant positive correlation between the hatching fraction of diapausing eggs and an index of habitat predictability.