Seed Germination in Desert Annuals: An Empirical Test of Adaptive Bet Hedging.

TLDR: A pattern of delayed germination consistent with among‐year bet‐hedging predictions arose in the field through the interaction of seed germinability and the distribution of environmental conditions during germination.

Abstract: Temporal variability in survivorship and reproduction is predicted to affect the evolution of life‐history characters. Desert annual plants experience temporal variation in reproductive success that is largely caused by precipitation variability. We studied several populations of the desert annual Plantago insularis along a precipitation gradient. Whereas models of bet hedging in unpredictable environments generally predict one optimal germination fraction for a population, empirical studies have shown that environmental conditions during germination can cause a range of germination fractions to be expressed. In a 4‐yr field study, we found that populations in historically more xeric environments had lower mean germination fractions, as is predicted by bet‐hedging models. However, populations exhibited significant variation in germination among years. Two experimental studies measuring germination under several environment conditions were conducted to elucidate the source of this in situ variati...