Evolutionary implications of fluctuating natural selection

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It has been said that the only reliable characteristic of natural environments is that they are constantly changing. Although it is well known that such changes can be of any magnitude and may occur over any time scale, much remains to be learned about how organisms cope with this variability. The research supported by this NSERC Discovery Grant will lead to progress in the basic understanding of response to environmental change. Aside from extinction, known outcomes of environmental change include direct responses such as range shifts and individual-level plastic adjustments within a lifetime, or may include long-term evolved responses such as "adaptive tracking" or the evolution of risk aversion ("bet-hedging") strategies over generations. Much is being learned about how individual species may respond to environmental change in isolation, but their response will partly be determined by how they respond when part of a species assemblage. One of the goals of this proposed research is to devise an experimental system to observe species mixtures, or assemblages, in a "microcosm" consisting of a thermal gradient, and then forcing the assemblage to adjust to a change in this thermal gradient. This will also allow the researchers to assess the relative importance of different evolutionary and ecological processes to the outcome. Other studies of the evolution of reproduction under environmental variance will provide fundamental knowledge of organismal response to changing conditions. For example, so-called "bet hedging" is an adaptation to unpredictable change itself. Humans make conscious decisions to sacrifice immediate gain by "hedging their bets" against risk in an unpredictable world (the purchase of insurance is an example). Because natural environments are also unpredictable, bet-hedging traits are expected to evolve through natural selection because they reduce the risk of failure. This topic is thus of interest to those concerned with any aspect of environmental change. Although bet hedging has been acknowledged in the theoretical literature as a general response to change, its relevance to response to future climate change is being studied for the first time.