Adaptation in response to environmental unpredictability

Franch‐Gras, Lluis; García‐Roger, Eduardo M.; Serra, Manuel; Carmona, Marı́a José

doi:10.1098/rspb.2017.0427

Cited by 50 publications

(91 citation statements)

References 76 publications

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“…There is likely to be a strong genetic component to the mixis response to population density. Different strains or populations, and different clones within a population, can have different mixis thresholds or maximum mixis ratios (Carmona, Dimas‐Flores, García‐Roger, & Serra, ; Franch‐Gras, García‐Roger, Serra, & Carmona, ; Snell, ; see Section 6.2.2). Also, physiological or endogenous factors can affect the mixis response.…”

Section: Sex In Laboratory Populationsmentioning

confidence: 99%

“…Franch‐Gras et al () compared mixis thresholds of B. plicatilis populations from nine shallow, saline ponds. Some ponds were flooded for years; others frequently dried and filled up again.…”

Section: Propensity For Sex During Sexual Periodsmentioning

confidence: 99%

“…The mixis threshold is very variable: 25-70 individuals/L in many rotifers, as low as c. 4 individuals/L in one rotifer, and as high as c. 200 individuals/L in others (see Cieplinski, Weisse, & Obertegger, 2019;Gilbert & Diéguez, 2010 There is likely to be a strong genetic component to the mixis response to population density. Different strains or populations, and different clones within a population, can have different mixis thresholds or maximum mixis ratios (Carmona, Dimas-Flores, García-Roger, & Serra, 2009;Franch-Gras, García-Roger, Serra, & Carmona, 2017;Snell, 1987; see Section 6.2.2). Also, physiological or endogenous factors can affect the mixis response.…”

Section: Population Densitymentioning

confidence: 99%

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Variation in the life cycle of monogonont rotifers: Commitment to sex and emergence from diapause

Gilbert

2019

Freshwater Biology

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A review of research on life‐cycle events in field and laboratory populations of monogonont rotifers shows that there is great variation at multiple levels: (1) degree of sexual dimorphism; (2) occurrence and timing of sex; (3) propensity for sex during sexual periods; (4) factors controlling initiation of sex; and (5) timing and extent of emergence from diapause. There is no regular pattern where: (1) fertilised resting eggs hatch to start the growing season; (2) populations develop via female parthenogenesis during favourable conditions; and then (3) bisexual reproduction with resting‐egg production occurs during later, unfavourable conditions. Sexual reproduction in natural populations can occur throughout much of the growing season, be restricted to some period(s) during the growing season, or be completely absent. During sexual reproduction in both natural and laboratory populations, only some fraction of females produces males or resting eggs. This bet‐hedging strategy can prevent a population crash and permits future population growth via female parthenogenesis. Selection against sexual reproduction, and rapid loss of sex, can occur. Laboratory experiments with pond‐dwelling species have identified specific environmental factors that induce sex in different species: (1) increasing population density; (2) dietary tocopherol (vitamin E) and (3) long photoperiods. These factors generally are associated with favourable conditions for population growth and production of energy‐rich resting eggs: (1) large population size; (2) high probability of contacts between males and fertilisable females; and (3) nutritious diets. Endogenous factors can inhibit responses to these environmental inducers, and thus favour female parthenogenesis. The timing of resting‐egg hatching depends on: (1) occurrence of specific environmental conditions; (2) the minimum duration of obligate diapause; and (3) the genotype and physiology of females producing resting eggs. Hatching may occur shortly after oviposition, after a long diapause before or at the start of a new growing season, or throughout the growing season. Hatching can be massive and contribute substantially to population growth and genetic diversity. Areas for future research include: (1) determining the timing and extent of sex and resting‐egg hatching in more natural populations, especially those that are marine, benthic, sessile, and interstitial; and (2) identifying environmental and physiological factors controlling these events.

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Section: Sex In Laboratory Populationsmentioning

confidence: 99%

Section: Propensity For Sex During Sexual Periodsmentioning

confidence: 99%

Section: Population Densitymentioning

confidence: 99%

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Variation in the life cycle of monogonont rotifers: Commitment to sex and emergence from diapause

Gilbert

2019

Freshwater Biology

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“…The fitter individuals could allow the population to persist in a novel environment, and provide the material for selection to act upon (Ghalambor et al, 2007). This scenario is reminiscent of "bet-hedging"-if it is unclear which single phenotype will maximize fitness in the next generation, betting on a wide range of phenotypes might pay off (Franch-Gras, García-Roger, Serra, & Carmona, 2017;Starrfelt & Kokko, 2012). Potentially, variability itself could be heritable, which might allow these variants to keep up with rapidly changing environments via "heritable bet-hedging" (O'Dea et al, 2016;Pal & Miklos, 1999).…”

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confidence: 99%

Developmental temperature affects phenotypic means and variability: A meta‐analysis of fish data

2019

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Fishes are sensitive to their thermal environment and face an uncertain future in a warming world. Theoretically, populations in novel environments might express greater levels of phenotypic variability to increase the chance of surviving—and eventually thriving—in the new conditions. Most research on the effect of the early thermal environment in fish species focuses on average phenotypic effects rather than phenotypic variability, but to understand how fishes will respond to rising temperatures we need to consider both the average response of the population, as well as the breadth of individual responses. Here we present the first meta‐analysis on the effects of developmental temperature in fishes. Using data from 43 species and over 6,000 individual fish, we show that a change in developmental temperature induces a significant change in phenotypic means and variability, but differently depending on whether the temperature is increased or decreased. Decreases in temperature (cool environments) showed a significant decrease in phenotypic means and no change in phenotypic variability. Increases in temperature (warm environments) showed a non‐significant increase in phenotypic means and a marginally significant increase in phenotypic variability. Larger increases in temperature saw greater increases in phenotypic variability, but no increase in the mean phenotypic response. Together, our results suggest that fishes exhibit both directed and stochastic developmental plasticity in response to warming temperatures, which could facilitate or accelerate adaptation to a changing environment.

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“…Evolutionary biologists have long recognized that strategies lowering arithmetic mean fitness can be selected for if they also lower genotype variance in fitness, thereby increasing geometric mean fitness (Levins 1962;Lewontin and Cohen 1969;Gillespie 1974). Such strategies are known as bet-hedging (Slatkin 1974;Seger and Brockmann 1987) and have gained a lot of interest in recent years, from theoreticians and empiricists alike (Simons 2011;Starrfelt and Kokko 2012;Crowley et al 2016;Franch-Gras et al 2017;Haaland et al 2019b). Bet-hedging operates at the long-term genotype level, and can thus differ substantially from short-term individual optimization (Yoshimura and Clark 1991;McNamara 1998;Haaland and Botero 2019).…”

Section: Introductionmentioning

confidence: 99%

Individual reversible plasticity as a genotype-level bet-hedging strategy

Haaland

Wright

Ratikainen

2020

Preprint

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Reversible plasticity in phenotypic traits allows organisms to cope with environmental variation within lifetimes, but costs of plasticity may limit just how well the phenotype matches the environmental optimum.An additional adaptive advantage of plasticity might be to reduce fitness variance, or bet-hedging to maximize geometric (rather than simply arithmetic) mean fitness. Here we model the evolution of reaction norm slopes, with increasing costs as the slope or degree of plasticity increases. We find that greater investment in plasticity (i.e. steeper reaction norm slopes) is favoured in scenarios promoting bet-hedging as a response to multiplicative fitness accumulation (i.e. coarser environmental grains and fewer time steps prior to reproduction), because plasticity lowers fitness variance across environmental conditions. In contrast, in scenarios with finer environmental grain and many time steps prior to reproduction, bet-hedging plays less of a role and individual-level optimization favours evolution of shallower reaction norm slopes.We discuss contrasting predictions from this partitioning of the different adaptive causes of plasticity into short-term individual benefits versus long-term genotypic (bet-hedging) benefits under different costs of plasticity scenarios, thereby enhancing our understanding of the evolution of optimum levels of plasticity in examples from thermal physiology to advances in avian lay dates. Impact summaryPhenotypic plasticity is a key mechanism by which organisms cope with environmental change. Plasticity relies on the existence of some reliable environmental cue that allows organisms to infer current or future conditions, and adjust their traits in response to better match the environment. In contrast, when environmental fluctuations are unpredictable, bet-hedging favours lineages that persist by lowering their fitness variance, either among or within individuals. Plasticity and bet-hedging are therefore often considered to be alternative modes of adaptation to environmental change. However, we here make the point that plasticity also has the capacity to change an organism's variance in fitness across different environmental conditions, and could thus itself be part ofand not an alternative toa bet-hedging strategy.We show that bet-hedging at the genotype level affects the optimal degree of plasticity that individuals use to track environmental fluctuations, because despite a reduction in expected fitness at the individual level, costly investment in the ability to be plastic also lowers variance in fitness. We also discuss alternative predictions that arise from scenarios with different types of costs of plasticity. Evolutionary bet-hedging and phenotypic plasticity are both topics experiencing a renewed surge of interest as researchers seek to better integrate different adaptations to ongoing rapid environmental change in a range of areas of literature within ecology and evolution, including behavioural ecology, evolutionary physiology and life-history theory. We believe that...

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Adaptation in response to environmental unpredictability

Cited by 50 publications

References 76 publications

Variation in the life cycle of monogonont rotifers: Commitment to sex and emergence from diapause

Variation in the life cycle of monogonont rotifers: Commitment to sex and emergence from diapause

Developmental temperature affects phenotypic means and variability: A meta‐analysis of fish data

Individual reversible plasticity as a genotype-level bet-hedging strategy

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