Trophic interactions drive the emergence of diel vertical migration patterns: a game-theoretic model of copepod communities

Diel Vertical Migration (DVM), the daily movement of organisms through oceanic water columns, is mainly driven by spatio-temporal variations in light affecting the intensity of predator-prey interactions. Migration patterns of an organism are intrinsically linked to the distribution of its conspecifics, its prey, and its predators, each with their own fitness seeking imperatives. We present a mechanistic, trait-based model of DVM for the different components of a pelagic community. Specifically we consider size, sensory mode, and feeding mode as key traits, representing a community of copepods that prey on each other and are, in turn, preyed upon by fish. Using game theoretic principles, we explore the optimal distribution of the main groups of a planktonic pelagic food-web simultaneously. Within one single framework, our model reproduces a whole suite of observed patterns, such as size-dependent DVM patterns of copepods and reverse migrations. These patterns can only be reproduced when different trophic levels are considered at the same time. This study facilitates a quantitative understanding of the drivers of DVM, and is an important step towards mechanistically underpinned predictions of DVM patterns and biologically mediated carbon export.

昼夜垂直迁移（Diel Vertical Migration，DVM）指生物在海洋水层中每日往返移动的行为，其主要驱动力为光照的时空变化——该变化会调控捕食者与猎物间互动的强度。生物的迁移模式与其同类、猎物及捕食者的分布存在内在关联，而每一类群均有各自的适合度追求目标。本研究针对浮游生物群落的不同组成部分，提出了一种基于性状的DVM机制模型。具体而言，我们将体型、感知模式与摄食模式作为核心性状，该模型的研究对象为一类相互捕食、同时又会被鱼类捕食的桡足类群落。我们借助博弈论原理，同时探索了浮游食物网主要类群的最优分布模式。在单一统一的框架下，我们的模型能够复现一系列已被观测到的典型现象，例如桡足类的体型依赖性昼夜垂直迁移模式以及反向迁移行为。仅当同时考虑不同营养级时，这些迁移模式才能被成功复现。本研究有助于定量理解昼夜垂直迁移的驱动机制，同时为基于机制的DVM模式预测以及生物介导的碳输出研究迈出了重要一步。