Rapid environmental change in games: complications and counter-intuitive outcomes

Andrew Sih,Richard McElreath,Pete C. Trimmer,Brendan J. Barrett

doi:10.1038/s41598-019-43770-x

Abstract

Human-induced rapid environmental change (HIREC) has recently led to alterations in the fitness and behavior of many organisms. Game theory is an important tool of behavioral ecology for analyzing evolutionary situations involving multiple individuals. However, game theory bypasses the details by which behavioral phenotypes are determined, taking the functional perspective straight from expected payoffs to predicted frequencies of behaviors. In contrast with optimization approaches, we identify that to use existing game theoretic models to predict HIREC effects, additional mechanistic details (or assumptions) will often be required. We illustrate this in relation to the hawk-dove game by showing that three different mechanisms, each of which support the same ESS prior to HIREC (fixed polymorphism, probabilistic choice, or cue dependency), can have a substantial effect on behavior (and success) following HIREC. Surprisingly, an increase in the value of resources can lead to a reduction in payoffs (and vice versa), both in the immediate- and long-term following HIREC. An increase in expected costs also increases expected payoffs. Along with these counter-intuitive findings, this work shows that simply understanding the behavioral payoffs of existing games is insufficient to make predictions about the effects of HIREC.

Highlights

Human-induced rapid environmental change (HIREC) poses a threat to the persistence of many species and populations through factors such as climate change, habitat loss or fragmentation, increased human harvesting, exposure to novel biotic or abiotic stressors and/or availability of novel, inappropriate resources
While the above approach allows decision-making of an individual to be analyzed both before and after HIREC, it ignores the game theory aspect that can be important for many interactive situations
We have shown that altering the value of resources can have counter-intuitive effects

Summary

Hawk Dove

The approach that we adopt assumes that individuals exhibit behavioral plasticity guided by previously adaptive cue-response systems, but that the pattern of plasticity can be maladaptive due to evolutionary mismatch. The reaction norm is the ESS response to the conditions by each individual in the population, and does best if the environmental change decreases V, if the value of resources were to increase from the baseline value (of 1), the reaction norm would result in a lower expected payoff than under the other strategies The outcome of this plastic response (where they shift their behavior adaptively in response to HIREC changes in V) is perhaps surprising. This result is general; as discussed above, under this strategy, both hawks and doves get the same expected payoff of (1 − V/C)V/2. The effect of evolved mechanism (supporting the pre-HIREC ESS) on payoffs immediately following a change in the cost of contest This shows the effect of altering C for genetic polymorphisms, probabilistic choice or an optimal reaction norm. This is not a necessary condition though; we identify in Supplementary Information 2 that a mechanism of decision would be required to predict outcomes following HIREC in an iterated Prisoner’s Dilemma game, where negative frequency-dependence does not apply (cooperators don’t do better when there are more defectors)

Discussion

Findings

Additional Information