Abstract
Variability in the environment defines the structure and dynamics of all living systems, from organisms to ecosystems. Species have evolved traits and strategies that allow them to detect, exploit and predict the changing environment. These traits allow organisms to maintain steady internal conditions required for physiological functioning through feedback mechanisms that allow internal conditions to remain at or near a set-point despite a fluctuating environment. In addition to feedback, many organisms have evolved feedforward processes, which allow them to adjust in anticipation of an expected future state of the environment. Here we provide a framework describing how feedback and feedforward mechanisms operating within organisms can generate effects across scales of organization, and how they allow living systems to persist in fluctuating environments. Daily, seasonal and multi-year cycles provide cues that organisms use to anticipate changes in physiologically relevant environmental conditions. Using feedforward mechanisms, organisms can exploit correlations in environmental variables to prepare for anticipated future changes. Strategies to obtain, store and act on information about the conditional nature of future events are advantageous and are evidenced in widespread phenotypes such as circadian clocks, social behaviour, diapause and migrations. Humans are altering the ways in which the environment fluctuates, causing correlations between environmental variables to become decoupled, decreasing the reliability of cues. Human-induced environmental change is also altering sensory environments and the ability of organisms to detect cues. Recognizing that living systems combine feedback and feedforward processes is essential to understanding their responses to current and future regimes of environmental fluctuations.This article is part of the theme issue ‘Integrative research perspectives on marine conservation’.
Highlights
Global change is characterized by trends, cycles and variability in the environment on land and in the oceans
Feedback and feedforward systems have been the focus of a great deal of research in complex system science, engineering and theoretical biology (e.g. [56,57]). This is just one way of understanding how feedback and feedforward processes have shaped systems to respond to fluctuating environments, and it is meant as a framework to locate the focus of future analysis, to guide inquiry about change in ecological systems and to facilitate comparisons among systems
While distinguishing between feedbacks that arise via natural selection versus those occur owing to other mechanisms is important to understanding how they may change as the environment changes, considering feedbacks in multiple forms allows us to understand the processes that affect persistence of living systems at multiple levels of organization, from cells to ecosystems
Summary
Global change is characterized by trends, cycles and variability in the environment on land and in the oceans. Environments that are dominated by variation at low frequencies (i.e. cycles with long periods, high temporal autocorrelation; box 1, figure 1) are more predictable to organisms living in them because current conditions are likely to be accurate predictors of near-term future conditions. A cue early in a season can allow organisms to anticipate future favourable conditions for reproduction, migration or development, and initiate the biological processes that will allow these life-history events to occur at the time of favourable conditions In this way, organisms can match their phenotype to expected environmental conditions, increasing their fitness [27]. Organisms can exploit repeated associations between correlated environmental variables with a time lag to anticipate change In this example, x is an event (i.e. a decrease in oxygen) that occurs in some random temporal sequence (a), as evidenced by the large variation in the time lags between successive x events, τx (a,d, top panel). This is just one way of understanding how feedback and feedforward processes have shaped systems to respond to fluctuating environments, and it is meant as a framework to locate the focus of future analysis, to guide inquiry about change in ecological systems and to facilitate comparisons among systems
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