Data from: Adaptive evolution to novel predators facilitates the evolution of damselfly species range shifts

Most species have evolved adaptations to reduce the chances of predation. In many cases adaptations to coexist with one predator generate tradeoffs in the ability to live with other predators. Consequently, the ability to live with one predator may limit the geographic distributions of species, such that adaptive evolution to coexist with novel predators may facilitate range shifts. In a case study with Enallagma damselflies, we used a comparative phylogenetic approach to test the hypothesis that adaptive evolution to live with a novel predator facilitates range size shifts. Our results suggest that the evolution of Enallagma shifting from living in ancestral lakes with fish as top predators, to living in lakes with dragonflies as predators, may have facilitated an increase in their range sizes. This increased range size likely arose because lakes with dragonflies were widespread, but unavailable as a habitat throughout much of the evolutionary history of Enallagma because they were historically maladapted to coexist with dragonfly predators. Additionally, the traits that have evolved as defenses against dragonflies also likely enhanced damselfly dispersal abilities. While many factors underlie the evolutionary history of species ranges, these results suggest a role for the evolution of predator-prey interactions.

绝大多数物种都演化出了反捕食适应策略，以降低被捕食的概率。在诸多情形下，为与某一类捕食者共存而演化出的适应策略，会对物种应对其他捕食者的生存能力产生权衡效应。因此，能够与某一类捕食者共存的能力，会限制物种的地理分布范围；这意味着，为应对新型捕食者而发生的适应性演化，或许会推动物种分布范围的扩张。在针对蟌属（Enallagma）豆娘（damselflies）的案例研究中，我们采用比较系统发育分析方法（comparative phylogenetic approach），验证了"为应对新型捕食者而发生的适应性演化可推动物种分布范围扩张"这一假说。我们的研究结果显示，蟌属物种从祖先栖息的以鱼类为顶级捕食者的湖泊，转移至以蜻蜓为捕食者的湖泊的演化过程，或许推动了其分布范围的扩张。这类分布范围的扩张，可能源于以蜻蜓为捕食者的湖泊本就广泛分布，但在蟌属演化史的大部分时期，这类栖息地并不适宜其生存——因为它们在历史上无法适应与蜻蜓捕食者共存。此外，为抵御蜻蜓捕食而演化出的防御性状，或许也提升了豆娘的扩散能力。尽管物种分布范围的演化历史受诸多因素共同影响，但本研究结果表明，捕食者-猎物相互作用（predator-prey interactions）的演化在其中发挥了一定作用。