Title: Bet-hedging against demographic fluctuations,
Abstract: Biological organisms have to cope with stochastic variations in both the
external environment and the internal population dynamics. Theoretical studies
and laboratory experiments suggest that population diversification could be an
effective bet-hedging strategy for adaptation to varying environments. Here we
show that bet-hedging can also be effective against demographic fluctuations
that pose a trade-off between growth and survival for populations even in a
constant environment. A species can maximize its overall abundance in the long
term by diversifying into coexisting subpopulations of both "fast-growing" and
"better-surviving" individuals. Our model generalizes statistical physics
models of birth-death processes to incorporate dispersal, during which new
populations are founded, and can further incorporate variations of local
environments. In this way we unify different bet-hedging strategies against
demographic and environmental variations as a general means of adaptation to
both types of uncertainties in population growth.