Life-History Evolution in Uncertain Environments: Bet Hedging in Time

Abstract

Many vertebrates, forest herbs, and trees exhibit both variable age at maturity and iteroparity as adaptations to uncertain environments. We analyze a stochastic model that combines these two life-history adaptations with density-dependent fertility. Results for a model with only iteroparity are consistent with previous work; environmental uncertainty favors adult survival over juvenile survival. This holds true even if there is a moderately strong convex trade-off between adult survival and fecundity, but the direction of selection can depend on which life-history trait is considered a random variable. A life history with only developmental delay favors juvenile survival in uncertain environments, consistent with previous models of seed banks. When both developmental delay and iteroparity are included in the model, both adaptations are favored in uncertain environments. Our simulations show that selection is not necessarily a runaway process in which either developmental delay or iteroparity is favored, as recently proposed by Tuljapurkar and Wiener, but rather that selection can favor both mechanisms. Invasion analysis shows that selective pressure on life-history delays increases as environmental variation increases. Reproductive delay and adult survival can be either adaptations or constraints. Natural-history studies that estimate model parameters can resolve this uncertainty.

Evolution of alternative insect life histories in stochastic seasonal environments

“…2000; Tuljapurkar and Wiener 2000; Halkett et al. 2004; Wilbur and Rudolf 2006; Koons et al. 2008; Rajon et al.…”

“…Life history theory predicts that temporal uncertainty of the environment favors temporal dispersion of reproduction (i.e., iteroparity; Schaffer 1974a; Tuljapurkar and Wiener 2000; Wilbur and Rudolf 2006; but see Orzack and Tuljapurkar 1989) and/or variable or delayed time of maturation (Cohen 1966; Tuljapurkar 1990; Tuljapurkar and Istock 1993; Menu et al. 2000; Tuljapurkar and Wiener 2000; Wilbur and Rudolf 2006; Koons et al. 2008).…”

Altitudinal effects on the life history of the Anatolian lizard(Apathya cappadocica, Werner 1902) from southeastern Anatolia, Turkey

“…Traditionally, life history traits are quantified in terms of age and body size. Both of these measurements have unique implications for a given life history trait (Davidowitz et al, 2005;Wilbur and Rudolf, 2006). Age and body size of individuals are 2 standard characteristics that many researchers (Chen et al, 2011;Gül et al, 2011;Chen et al, 2012;Lou et al, 2012;Özdemir et al, 2012;Altunışık et al, 2013;Huang et al, 2013;Gül et al, 2014) have used to quantify life history traits.…”

Modes, mechanisms and evidence of bet hedging in rotifer diapause traits

“…However, in the real world, more than one trait can be involved in the adaptation to environmental unpredictability, as several traits can mediate the same bet-hedging response (Wilbur & Rudolf, 2006;Childs et al, 2010). For instance, both a conservative bethedging strategy in the timing of sex and a diversified strategy in the duration of diapause likely serve the same objective of avoiding the risk of a complete reproductive failure in habitats with an unpredictable length of the growing season.…”

“…For instance, both a conservative bethedging strategy in the timing of sex and a diversified strategy in the duration of diapause likely serve the same objective of avoiding the risk of a complete reproductive failure in habitats with an unpredictable length of the growing season. Because both traits have essentially the same bet-hedging role, it is interesting to ask which should evolve or whether selection of both traits is possible (Wilbur & Rudolf, 2006). For instance, if the sediments are risky because deterioration in the egg banks is very high (García-Roger et al, 2006a, c), then an early induction of sex to ensure the production of a new cohort of diapausing eggs would be a less costly bet-hedging strategy.…”