scholarly journals Modes of response to environmental change and the elusive empirical evidence for bet hedging

2011 ◽  
Vol 278 (1712) ◽  
pp. 1601-1609 ◽  
Author(s):  
Andrew M. Simons
Keyword(s):  
Environmental Change ◽  
Empirical Evidence ◽  
Natural Environments ◽  
Bet Hedging ◽  
Fluctuating Selection ◽  
Hedging Strategies ◽  
Evolutionary Response ◽  
Human Decision ◽  
Response To Environmental Change

Uncertainty is a problem not only in human decision-making, but is a prevalent quality of natural environments and thus requires evolutionary response. Unpredictable natural selection is expected to result in the evolution of bet-hedging strategies, which are adaptations to long-term fluctuating selection. Despite a recent surge of interest in bet hedging, its study remains mired in conceptual and practical difficulties, compounded by confusion over what constitutes evidence for its existence. Here, I attempt to resolve misunderstandings about bet hedging and its relationship with other modes of response to environmental change, identify the challenges inherent to its study and assess the state of existing empirical evidence. The variety and distribution of plausible bet-hedging traits found across 16 phyla in over 100 studies suggest their ubiquity. Thus, bet hedging should be considered a specific mode of response to environmental change. However, the distribution of bet-hedging studies across evidence categories—defined according to potential strength—is heavily skewed towards weaker categories, underscoring the need for direct appraisals of the adaptive significance of putative bet-hedging traits in nature.

Behavioral, plastic, and evolutionary responses to a changing world

2018 ◽  
Author(s):  
Wolf U. Blanckenhorn
Keyword(s):  
Climate Change ◽  
Life History ◽  
Environmental Change ◽  
Physiological Responses ◽  
Short Term ◽  
Temporal Scales ◽  
Evolutionary Response ◽  
Physiological Adjustments ◽  
Changing World

Organisms can respond to environmental change by modifying their behavior to obtain an instant response, through short-term phenotypically plastic, often physiological, adjustments, and/or by adapting their life history through a more long-term evolutionary response. Behavioural and physiological responses, in fact, can occur at all these three temporal scales. Examples of behaviors so affected include congregation, dispersal, foraging, migration, or mating. Such responses have consequences at the population and community levels, and ultimately for the evolution of species. This chapter discusses insect examples of these kinds, with an emphasis on human-induced factors, such as (primarily) climate change, pollution, fragmentation, and urbanization.

scholarly journals Fluctuating natural selection accounts for the evolution of diversification bet hedging

2009 ◽  
Vol 276 (1664) ◽  
pp. 1987-1992 ◽  
Author(s):  
Andrew M. Simons
Keyword(s):  
Seed Germination ◽  
Time Scales ◽  
Geometric Mean ◽  
Empirical Support ◽  
Natural Environments ◽  
Bet Hedging ◽  
Fluctuating Selection ◽  
Quantitative Test ◽  
Geometric Mean Fitness ◽  
Germination Timing

Natural environments are characterized by unpredictability over all time scales. This stochasticity is expected on theoretical grounds to result in the evolution of ‘bet-hedging’ traits that maximize the long term, or geometric mean fitness even though such traits do not maximize fitness over shorter time scales. The geometric mean principle is thus central to our interpretation of optimality and adaptation; however, quantitative empirical support for bet hedging is lacking. Here, I report a quantitative test using the timing of seed germination—a model diversification bet-hedging trait—in Lobelia inflata under field conditions. In a phenotypic manipulation study, I find the magnitude of fluctuating selection acting on seed germination timing—across 70 intervals throughout five seasons—to be extreme: fitness functions for survival are complex and multimodal within seasons and significantly dissimilar among seasons. I confirm that the observed magnitude of fluctuating selection is sufficient to account for the degree of diversification behaviour characteristic of individuals of this species. The geometric mean principle has been known to economic theory for over two centuries; this study now provides a quantitative test of optimality of a bet-hedging trait in nature.

Response of green hydra (Hydra viridissima) to variability and directional changes in food availability

Biologia ◽  
2015 ◽  
Vol 70 (10) ◽  
Author(s):  
Márta E. Rosa ◽  
Flóra Bradács ◽  
Jácint Tökölyi
Keyword(s):  
Environmental Change ◽  
Stress Tolerance ◽  
Food Availability ◽  
Environmental Changes ◽  
Control Group ◽  
Delayed Response ◽  
Natural Environments ◽  
Feeding Frequency ◽  
Green Hydra ◽  
Response To Environmental Change

AbstractNatural environments tend to be variable resulting in alternating periods of high and low food availability. Therefore, animals have to be able to accommodate to sudden environmental changes by adjusting their physiology and behaviour to new conditions. We investigated how simulated food variability affects life history traits (asexual reproduction and stress tolerance) and response to environmental change in laboratory experiments with green hydra (Hydra viridissima). We assigned hydra into four groups differing in feeding frequency (high or low) and food regularity (random or stable). After 21 days of accommodation, feeding frequency was changed (increased or decreased) in half of each group, the other half was kept as a control group. Hydra showed a delayed response to environmental change (increased or decreased feeding frequency). This delay in response was greater under an unpredictable feeding scheme. Animals on a random scheme had lower budding rates and lower stress tolerance. Follow-up experiments suggest that this might be due to receiving food on subsequent days, since we found that animals fed daily have lower budding rates than those fed on alternate days. We hypothesize that frequent feeding might cause high levels of oxidative/xenobiotic stress which could overwhelm the defence system of these animals.

scholarly journals Short‐term insurance versus long‐term bet‐hedging strategies as adaptations to variable environments

Evolution ◽  
2018 ◽  
Vol 73 (2) ◽  
pp. 145-157 ◽  
Author(s):  
Thomas Ray Haaland ◽  
Jonathan Wright ◽  
Jarle Tufto ◽  
Irja Ida Ratikainen
Keyword(s):  
Bet Hedging ◽  
Short Term ◽  
Hedging Strategies ◽  
Variable Environments ◽  
Term Insurance

scholarly journals Evolutionary rescue can maintain an oscillating community undergoing environmental change

2013 ◽  
Vol 3 (6) ◽  
pp. 20130036 ◽  
Author(s):  
Gregor F. Fussmann ◽  
Andrew Gonzalez
Keyword(s):  
Environmental Change ◽  
Community Dynamics ◽  
Ecological Communities ◽  
Evolutionary Response ◽  
Evolutionary Rescue ◽  
Before And After ◽  
Internal Forces ◽  
Frequency Changes ◽  
Response To Environmental Change ◽  
Physiological Acclimation

The persistence of ecological communities is challenged by widespread and rapid environmental change. In many cases, persistence may not be assured via physiological acclimation or migration and so species must adapt rapidly in situ . This process of evolutionary rescue (ER) occurs when genetic adaptation allows a population to recover from decline initiated by environmental change that would otherwise cause extirpation. Community evolutionary rescue (CER) occurs when one or more species undergo a rapid evolutionary response to environmental change, resulting in the recovery of the ancestral community. Here, we study the dynamics of CER within a three-species community coexisting by virtue of resource oscillations brought about by nonlinear interactions between two species competing for a live resource. We allowed gradual environmental change to affect the traits that determine the strength and symmetry of the interaction among species. By allowing the component species to evolve rapidly, we found that: (i) trait evolution can allow CER and ensure the community persists by preventing competitive exclusion during environmental change, (ii) CER brings about a change in the character of the oscillations (period, amplitude) governing coexistence before and after environmental change, and (iii) CER may depend on evolutionary change that occurs simultaneously with or subsequently to environmental change. We were able to show that a change in the character of community oscillations may be a signature that a community is undergoing ER. Our study extends the theory on ER to a world of nonlinear community dynamics where—despite high-frequency changes of population abundances—adaptive evolutionary trait change can be gradual and directional, and therefore contribute to community rescue. ER may happen in real, complex communities that fluctuate owing to a mix of external and internal forces. Experiments testing this theory are now required to validate our predictions.

scholarly journals Spatial analysis shows that fishing enhances the climatic sensitivity of marine fishes

2008 ◽  
Vol 65 (5) ◽  
pp. 947-961 ◽  
Author(s):  
Chih-hao Hsieh ◽  
Christian S Reiss ◽  
Roger P Hewitt ◽  
George Sugihara
Keyword(s):  
Climate Variability ◽  
Environmental Change ◽  
Spatial Heterogeneity ◽  
Geographic Distribution ◽  
Fish Species ◽  
Larval Fish ◽  
Fish Stocks ◽  
Northeastern Pacific ◽  
Response To Environmental Change

We compare the changes in geographic distribution of exploited fish species versus unexploited ones living in the same environment. For this comparative study, we use the 50-year larval fish time series from the California Cooperative Oceanic Fisheries Investigations, which allows us to view fishing as a treatment effect in a long-term ecological experiment. Our results indicate that exploited species show a clearer distributional shift in response to environmental change than unexploited species, even after accounting for life history and ecological traits and phylogeny. The enhanced response (improved signal–noise ratio) to environmental change in exploited species may be a consequence of reduced spatial heterogeneity caused by fishery-induced age (size) truncation and the constriction of geographic distribution that accompanies fishing pressure. We suggest that reduced spatial heterogeneity can cause exploited populations to be more vulnerable to climate variability, an effect that could have considerable importance in the management of fish stocks. This is the first study to compare the geographic distributions of a large suite of exploited and unexploited fish species from the northeastern Pacific in response to climate variability.

scholarly journals Time-dependent fitness effects can drive bet-hedging populations extinct

2016 ◽  
Author(s):  
Eric Libby ◽  
William Ratcliff
Keyword(s):  
Resource Competition ◽  
Bet Hedging ◽  
Short Term ◽  
Time Intervals ◽  
Hedging Strategies ◽  
Diversification Strategies ◽  
Environmental Fluctuations ◽  
Long Time ◽  
Temporally Correlated

AbstractTo survive unpredictable environmental change, many organisms adopt bet-hedging strategies that trade short-term population growth for long-term fitness benefits. Because the benefits of bet-hedging may manifest over long time intervals, bet-hedging strategies may be out-competed by strategies maximizing short-term fitness. Here, we investigate the interplay between two drivers of selection, environmental fluctuations and competition for limited resources, on different bet-hedging strategies. We consider an environment with frequent disasters that switch between which phenotypes they affect in a temporally-correlated fashion. We determine how organisms that stochastically switch between phenotypes at different rates fare in both competition and survival. When disasters are correlated in time, the best strategy for competition is among the worst for survival. Since the time scales over which the two agents of selection act are significantly different, environmental fluctuations and resource competition act in opposition and lead populations to evolve diversification strategies that ultimately drive them extinct.

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