Evolution and behavioural responses to human-induced rapid environmental change

Abstract

Almost all organisms live in environments that have been altered, to some degree, by human activities. Because behaviour mediates interactions between an individual and its environment, the ability of organisms to behave appropriately under these new conditions is crucial for determining their immediate success or failure in these modified environments. While hundreds of species are suffering dramatically from these environmental changes, others, such as urbanized and pest species, are doing better than ever. Our goal is to provide insights into explaining such variation. We first summarize the responses of some species to novel situations, including novel risks and resources, habitat loss/fragmentation, pollutants and climate change. Using a sensory ecology approach, we present a mechanistic framework for predicting variation in behavioural responses to environmental change, drawing from models of decision-making processes and an understanding of the selective background against which they evolved. Where immediate behavioural responses are inadequate, learning or evolutionary adaptation may prove useful, although these mechanisms are also constrained by evolutionary history. Although predicting the responses of species to environmental change is difficult, we highlight the need for a better understanding of the role of evolutionary history in shaping individuals' responses to their environment and provide suggestion for future work.

Keywords: anthropogenic stressors; behaviour; detection theory; ecological traps; environmental change; exotic predators; habitat loss; sensory ecology.

Figure 1

Past environments provide the evolutionary history that shapes sensory and cognitive processes controlling behaviour, as well as other traits and genetic variation. The fit of behaviour and other traits along with novel environments (that might match or mismatch past environments) influence individual fitness that governs population performance. Variations in fitness and genetic variation drive evolution that feeds back to determine future sensory and cognitive processes, behaviour, other traits and genetic variation. These, in turn, loop back to influence future fitness and population performance.

Figure 2

Influence of cue similarity, and use of general versus specialized cues, on recognition of novel cues. Shown are two-dimenstional cue spaces. E = cues produced by a stimulus from a species’ evolutionary past; N = cues produced by a novel stimulus. The circle or oval around each E is the cue space that elicits a response. (A) The new cue is similar to cues from the species’ past, and the focal species uses specific cues to elicit a response. The species recognizes the novel stimulus. (B) The new cue is not similar to cues from the past, and the species uses specific cues. The species does not recognize the novel stimulus. (C) New and past cues are dissimilar, but because the species uses general cues, it recognizes the new stimulus. (D) Prey recognition of a predator depends on how they use multiple cues. Prey could be alarmed by either A or B (above a threshold level for either) or might require cue A and B to be alarmed. Adapted from Sih et al. (2010).

Figure 3

Three receiver operating characteristic (ROC) curves with discriminabilities of 0, 0.5 and 2. When discrimination is impossible (discriminability = 0), stimuli cannot affect behaviour, and the rate of successful detections equals the background response rate (1:1 line). As discriminability improves, these two rates can diverge and the ROC curve bows up and to the left. Organisms’ response probabilities are also influenced by their response bias – the level of confidence required to induce a response – which depends on the slope. The ‘X’ marks the organism considered in Figs 4 and 5, with discriminability = 2 and bias = −0.4.

Figure 4

The inferred distributions of perceived intensities from stimuli (right curve) and nonstimuli (left curve) for the organism marked in Fig 3. Discriminability is the relative distance between the curves and corresponds to low overlap, while bias is the strength of evidence required to provoke a response, corresponding to the relative height of the curves. The hatched areas under each curve correspond to the organism's response rate for the corresponding scenario (i.e., its x and y coordinates in ROC space).

Figure 5

Here, the ability of the organism from Figs 3 and 4 to discriminate stimuli from nonstimuli decreases from 2 to 0.5. If the organism maintains the threshold intensity required to induce a response, its background response rate remains unchanged as it moves down through ROC space. If the organism instead takes its poorer discriminability into account and maintains a constant bias, it must adjust its response rates by following the curved arrow as described in the text.