Evolution in interacting species alters predator life history traits, behavior and morphology in experimental microbial communities

Predator-prey interactions are key for the dynamics of many ecosystems. An
increasing body of evidence suggests that rapid evolution and co-evolution
can alter these interactions, with important ecological implications, by
acting on traits determining fitness, including reproduction,
anti-predatory defense and foraging efficiency. However, most studies to
date have focused only on evolution in the prey species, and the predator
traits in (co-)evolving systems remain poorly understood. Here we
investigated changes in predator traits after ~600 generations in a
predator-prey (ciliate-bacteria) evolutionary experiment. Predators
independently evolved on seven different prey species, allowing
generalization of the predator’s evolutionary response. We used highly
resolved automated image analysis to quantify changes in predator life
history, morphology and behavior. Consistent with previous studies, we
found that prey evolution impaired growth of the predator, although the
effect depended on the prey species. In contrast, predator evolution did
not cause a clear increase in predator growth when feeding on ancestral
prey. However, predator evolution affected morphology and behavior,
increasing size, speed and directionality of movement, which have all been
linked to higher prey search efficiency. These results show that in
(co-)evolving systems, predator adaptation can occur in traits relevant to
foraging efficiency without translating into an increased ability of the
predator to grow on the ancestral prey type.

捕食者-猎物（predator-prey）相互作用是诸多生态系统动态的核心驱动因素。日益增多的研究证据表明，快速演化与协同演化（co-evolution）可通过作用于决定物种适应度的各类性状——包括繁殖能力、反捕食防御策略以及觅食效率——来改变这类相互作用，并产生重要的生态学影响。然而，迄今为止绝大多数相关研究仅聚焦于猎物物种的演化过程，协同（共）演化系统中的捕食者性状仍未得到充分解析。本研究针对一项捕食者-猎物（纤毛虫-细菌）演化实验中历时约600代后的捕食者性状变化展开探究：捕食者在7种不同的猎物物种上独立演化，这为分析捕食者的通用演化响应提供了可能。我们采用高分辨率自动化图像分析技术，对捕食者的生活史、形态与行为特征变化进行定量表征。与既往研究结果一致，我们发现猎物演化会抑制捕食者的种群增长，但该效应因猎物物种的不同而存在差异。与之形成对照的是，当捕食者以祖先型猎物为食时，其自身的演化并未使其种群增长能力出现显著提升。不过，捕食者的演化确实改变了其形态与行为特征：运动体型、移动速度与运动方向性均有所提升，而这些特征均与更高的猎物搜寻效率密切相关。本研究结果表明，在协同（共）演化系统中，捕食者可在与觅食效率相关的性状上产生适应性演化，但这并不会使其以祖先型猎物为食时的种群增长能力得到增强。