Bet hedging in desert winter annual plants: optimal germination strategies in a variable environment

Abstract

In bet hedging, organisms sacrifice short-term success to reduce the long-term variance in success. Delayed germination is the classic example of bet hedging, in which a fraction of seeds remain dormant as a hedge against the risk of complete reproductive failure. Here, we investigate the adaptive nature of delayed germination as a bet hedging strategy using long-term demographic data on Sonoran Desert winter annual plants. Using stochastic population models, we estimate fitness as a function of delayed germination and identify evolutionarily stable strategies for 12 abundant species in the community. Results indicate that delayed germination meets the criteria as a bet hedging strategy for all species. Density-dependent models, but not density-independent ones, predicted optimal germination strategies that correspond remarkably well with observed patterns. By incorporating naturally occurring variation in seed and seedling dynamics, our results present a rigorous test of bet hedging theory within the relevant environmental context.

Experimental evolution of bet hedging under manipulated environmental uncertainty in Neurospora crassa

“…However, empirical evidence for bet hedging remains scant [12]. Evidence is restricted to demonstrations of interspecific divergence [13] or population differentiation [14,15] in putative bet-hedging traits across environments that differ in predictability, or the documentation of the evolution of candidate bet-hedging traits under conditions in which they may be advantageous [16,17], with very few strong studies confirming fitness benefits of putative bethedging traits under fluctuating conditions [18][19][20][21]. Tests of bet hedging under field conditions are difficult because they require evaluating both environmental variance and its fitness effects over multiple generations.…”

Predicting Evolutionarily Stable Strategies from Functional Responses of Sonoran Desert Annuals to Precipitation

“…For instance, the adaptive value of delaying germination depends on the risk of seed mortality [11,13], which can depend on seed traits (e.g., varying seed coat thickness).…”

“…Here, we build upon a density-dependent seed bank model of Gremer & Venable [11] that includes intraspecific competition to estimate long-term stochastic fitness for ten annual plants in the iconic Sonoran Desert winter annual community. Unlike Gremer & Venable [11], we directly model the effect of precipitation on plant yield for this water-limited system.…”

Maternal Environment Modulates Dormancy and Germination in Vaccaria hispanica

“…Unpredictable biotic and abiotic maternal environment may have a crucial role in determining germination fractions and seedling recruitment. Bet-hedging is an important strategy to reduce the risk of failure under environmental uncertainty [2]. Spreading germination over time by producing seeds with different dormancy and longevity can help reducing the risk of recruitment failure in any one year [3].…”

“…Spreading germination over time by producing seeds with different dormancy and longevity can help reducing the risk of recruitment failure in any one year [3]. It is well known that, seeds are less vulnerable to environmental stresses than seedlings [2].…”