Integrating environmental complexity and the plasticity-first hypothesis to study responses to human-altered habitats

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Human disturbance has devastated natural populations and ecosystems across the planet. Organisms can adapt to some of these changes, either through adaptations acquired by natural selection acting on existing genetic variation, or through phenotypic plasticity. Furthermore, individual phenotypic plasticity and population-level evolutionary adaptation might interact in a reciprocal relationship: phenotypic plasticity itself may evolve in response human disturbance, and the nature of those plastic responses might influence subsequent evolutionary adaptation (the plasticity-first hypothesis). For years biologists have emphasized the need to evaluate multiple environmental stressors when studying organisms' responses to human-induced rapid environmental change (HIREC). Given that these multiple stressors are likely to impact a variety of phenotypes simultaneously, there is also a particular need to study plasticity in response to numerous stressors (i.e. ‘multidimensional plasticity’). While current research has yielded great insight into how populations are adapting in the face of novel environmental challenges, there are clear gaps in our understanding of these mechanisms, such as why similar species, or even multiple populations of the same species, do not exhibit similar ecological or evolutionary responses to HIREC. Here, we argue that incorporating the plasticity-first hypothesis and multidimensional plasticity into ecological and evolutionary studies of HIREC may yield greater insight into some of these challenges. This is important considering that most phenotypes display multidimensional plasticity, and HIREC brings with it a suite of novel challenges. The goal of this review is to highlight the need for incorporating multiple environmental stressors when considering organismal responses to HIREC and emphasize the importance of multidimensional plasticity and the plasticity-first hypothesis as ways to study how these suites of ecological stressors may influence evolutionary trajectories following HIREC. We then end by laying out questions and predictions that may be useful to those who wish to incorporate these concepts into their research. © 2022 The Association for the Study of Animal Behaviour

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Animal Behaviour

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behavioural plasticity, human disturbance, phenotypic plasticity, plasticity-first hypothesis