Abstract
For organisms living in unpredictable environments, timing important life‐history events is challenging. One way to deal with uncertainty is to spread the emergence of offspring across multiple years via dormancy. However, timing of emergence is not only important among years, but also within each growing season. Here, we study the evolutionary interactions between germination strategies that deal with among‐ and within‐season uncertainty. We use a modelling approach that considers among‐season dormancy and within‐season germination phenology of annual plants as potentially independent traits and study their separate and joint evolution in a variable environment. We find that higher among‐season dormancy selects for earlier germination within the growing season. Furthermore, our results indicate that more unpredictable natural environments can counter‐intuitively select for less risk‐spreading within the season. Furthermore, strong priority effects select for earlier within‐season germination phenology which in turn increases the need for bet hedging through among‐season dormancy.
Highlights
Most organisms live in variable and unpredictable environments, making it challenging for individuals to schedule important life-history events such as emergence or reproduction
We show that dormancy compensates for within-season bet hedging from germination phenology
We study how dormancy affects the evolution of withinseason germination phenology by assuming that bad years do not occur (u 1⁄4 1), and individuals experience only uncertainty with respect to the start of favourable growing conditions
Summary
Most organisms live in variable and unpredictable environments, making it challenging for individuals to schedule important life-history events such as emergence or reproduction. Bet hedging is defined as a strategy that reduces variance in fitness at a cost of a lower arithmetic mean fitness (Starrfelt & Kokko 2012), and it potentially allows organisms to deal with unpredictable conditions. The evolution of bet hedging is typically studied at a single time scale, for example either across or within growing seasons, yet variable conditions occur over multiple time scales (Gremer et al 2016). We study how risk-spreading strategies that deal with unpredictability within a growing season interact with those dealing with across-season variability. Spreading germination of seeds (or hatching of eggs in case of animals) across years is an adaptation to stochastically varying growing seasons. Producing offspring with variable dormancy periods reduces the risk that all offspring germinate in a year with unfavourable conditions. Bet hedging via dormancy has been demonstrated in insects (Rajon et al 2014; Grantham et al 2016), rotifers (Tarazona et al 2017), fish (Furness et al 2015) and bacteria (Sturm & Dworkin 2015)
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