Bet hedging with seed banks
- Bet hedging is an evolutionary response to variable and unpredictable environments (like the desert!).
- We have sayings about bet hedging like, “A bird in the hand is worth two in the bush” or “Don’t put all your eggs in one basket.
- These capture the idea of giving up some potential gain to lower risk in a variable unpredictable environment.
- Desert annual plants bet hedge by holding back a fraction of seeds that do not germinate even when conditions are favorable.
- The greater the year-to-year variation in success in the growing life stage of a desert annual, the stronger the selection to lower the germination fraction and bet hedge with dormant seeds.
- Year-to year variation in reproduction (21 years of Tumamoc data) is driven by variation in growing season rainfall:
Yet species differ in their sensitivity to rainfall variation:
High variance species, which are more sensitive to variation in rainfall, should have lower germination fractions. Our long-term data show that they do:
This shows that delayed germination of desert annuals acts as a bet hedging strategy!
For more on bet hedging see:
Venable, D. L. 2007. Bet hedging in a guild of desert annuals. Ecology 88: 1086-1090. pdf
Gremer, J. R., and D. L. Venable. 2014. Bet hedging in desert winter annual plants: optimal germination strategies in a variable environment. Ecology Letters 17:380-387. pdf
Gremer, J. R., Kimball, S., and D. L. Venable. 2016. Within- and among-year germination in Sonoran Desert winter annuals: bet hedging and predictive germination in a variable environment. Ecology Letters 19:1209-1218. pdf