Raatz Michael, van Velzen Ellen, Gaedke Ursula
Institute of Biochemistry and Biology University of Potsdam Potsdam Germany.
Ecol Evol. 2019 Mar 5;9(7):3823-3836. doi: 10.1002/ece3.5006. eCollection 2019 Apr.
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.
全球变化威胁着由种群的持久性和动态性所塑造的生态系统功能的维持。研究表明，如果物种具有更大的性状适应性，其持久性就会增加。在此，我们研究性状适应性是否也会影响相互作用物种的种群动态稳健性，进而塑造由这些动态所驱动的生态系统功能的可靠性。我们将捕食者 - 猎物系统中的共同适应建模为由于进化或表型可塑性导致的捕食者攻击和猎物防御的变化。我们研究性状适应如何影响种群动态对环境参数的压力扰动以及针对物种丰度及其性状值的脉冲扰动的稳健性。种群动态的稳健性由恢复力、弹性和抵抗力来表征。除了采用针对脉冲扰动的恢复力和弹性的既定度量（灭绝概率和返回时间）外，我们提出翘曲距离作为一种针对压力扰动的抵抗力的新度量，它比较扰动前后种群动态的形状和幅度。正如预期的那样，我们发现种群动态的稳健性取决于适应速度，但方式并不简单。随着系统更快地回到扰动前状态，弹性随着适应速度的增加而增加。相反，中等适应速度会增强恢复力，因为此时性状适应会抑制生物量振荡。种群动态的抵抗力强烈取决于压力扰动的目标，这使得它与适应速度之间不存在简单的关系。总体而言，我们发现低稳健性往往与种群动态的高幅度同时出现。因此，幅度也可能表明其他具有类似动态的自然系统对扰动的稳健性。我们的研究结果表明，除了对抗灭绝之外，性状适应确实会强烈影响种群动态对压力和脉冲扰动的稳健性。
