Co‐adaptation impacts the robustness of predator–prey dynamics against perturbations

Abstract

Global change threatens the maintenance of ecosystem functions that are shaped by the persistence and dynamics of populations. It has been shown that the persistence of species increases if they possess larger trait adaptability. Here, we investigate whether trait adaptability also affects the robustness of population dynamics of interacting species and thereby shapes the reliability of ecosystem functions that are driven by these dynamics. We model co‐adaptation in a predator–prey system as changes to predator offense and prey defense due to evolution or phenotypic plasticity. We investigate how trait adaptation affects the robustness of population dynamics against press perturbations to environmental parameters and against pulse perturbations targeting species abundances and their trait values. Robustness of population dynamics is characterized by resilience, elasticity, and resistance. In addition to employing established measures for resilience and elasticity against pulse perturbations (extinction probability and return time), we propose the warping distance as a new measure for resistance against press perturbations, which compares the shapes and amplitudes of pre‐ and post‐perturbation population dynamics. As expected, we find that the robustness of population dynamics depends on the speed of adaptation, but in nontrivial ways. Elasticity increases with speed of adaptation as the system returns more rapidly to the pre‐perturbation state. Resilience, in turn, is enhanced by intermediate speeds of adaptation, as here trait adaptation dampens biomass oscillations. The resistance of population dynamics strongly depends on the target of the press perturbation, preventing a simple relationship with the adaptation speed. In general, we find that low robustness often coincides with high amplitudes of population dynamics. Hence, amplitudes may indicate the robustness against perturbations also in other natural systems with similar dynamics. Our findings show that besides counteracting extinctions, trait adaptation indeed strongly affects the robustness of population dynamics against press and pulse perturbations.

Poikilosis – pervasive biological variation

“…Some examples of biological heterogeneity include stochastic gene expression 1 , DNA sequence differences that lead to >10,000 amino acid substitutions in each individual in comparison to human reference sequence 2 , variants in one gene may be related to several diseases 3 and one variant can lead to different phenotypes 4 , differences between individual genomes and in comparison to pangenome 5 , heterogeneity of isogenic bacteria 6 and human cells 7 , protein structural flexibility 8 and dynamics 9 , fluctuating enzyme catalytic rates 10 , heterogeneity in cellular machineries like ribosomes 11 , differences in protein post translational modifications 12 , asymmetric inheritance of degradative machineries and cell fates 13 , protein abundance differences between individuals including twins 14 , phenotypic plasticity 15 , continuum of sex 16 , incomplete penetrance of diseases 17 , differential cellular 18 and individual 19 drug responses, diversity of gut microbiota 20 , and predator-prey dynamics 21 . Phenotypic and genetic variation 22 and ecological heterogeneity 23 , 24 have been extensively reviewed.…”

Functional diversity alters the effects of a pulse perturbation on the dynamics of tritrophic food webs

“…In this way, morphological, physiological or behavioral individual characteristics are linked to a certain function, such as growth rate or nutrient uptake (Garnier, Navas, and Grigulis, 2016), and depend on each other by trade-offs to determine the overall fitness (McGill et al, 2006; Violle et al, 2007). This approach makes explicit how trait changes can feed back to population and food web dynamics, and partly regulate the response of food webs to environmental changes (Yamamichi and Miner, 2015; Theodosiou, Hiltunen, and Becks, 2019; Raatz, Velzen, and Gaedke, 2019).…”

“…Most studies investigating the responses of food webs to perturbations are restricted to multitrophic systems where only one or two trophic levels may adapt (Persson et al, 2001; Kovach-Orr and Fussmann, 2013), or to strictly bitrophic systems (Jones, 2008; Fussmann and Gonzalez, 2013; Yamamichi, Yoshida, and Sasaki, 2011; Bell et al, 2019; Govaert et al, 2019; Raatz, Velzen, and Gaedke, 2019). These studies underline how functional diversity at one or two trophic levels generally enhances the ecosystem’s ability to buffer against perturbations, and that the effects of functional diversity can be modulated at different trophic levels.…”

“…External disturbances come in a variety of forms, and each can affect the food web and its functions in different ways. Broadly, external disturbances can be separated into two types, called press and pulse perturbations (Tilman and Downing, 1996; Raatz, Velzen, and Gaedke, 2019). Press perturbations are long-term or permanent changes to a system component, such as increased harvesting or warming.…”

“…The response of a tritrophic food web to a nutrient pulse is characterized by several aspects, which are measured by different quantities. Analogous to Grimm andWissel, 1997 andRaatz, Velzen, and, the following terms are used:…”