Leigh Marine Laboratory, Institute of Marine Science, University of Auckland, Leigh, New Zealand
Leigh Marine Laboratory, Institute of Marine Science, University of Auckland, Leigh, New Zealand.
Proc Biol Sci. 2017 Nov 15;284(1866). doi: 10.1098/rspb.2017.1440.
Many prey species induce defences in direct response to predation cues. However, prey defences could also be enhanced by predators indirectly via mechanisms that increase resource availability to prey, e.g. trophic cascades. We evaluated the relative impacts of these direct and indirect effects on the mechanical strength of the New Zealand sea urchin We measured crush-resistance of sea urchin tests (skeletons) in (i) two marine reserves, where predators of sea urchins are relatively common and have initiated a trophic cascade resulting in abundant food for surviving urchins in the form of kelp, and (ii) two adjacent fished areas where predators and kelps are rare. Sea urchins inhabiting protected rocky reefs with abundant predators and food had more crush-resistant tests than individuals on nearby fished reefs where predators and food were relatively rare. A six-month long mesocosm experiment showed that while both food supply and predator cues increased crush-resistance, the positive effect of food supply on crush-resistance was greater. Our results demonstrate a novel mechanism whereby a putative morphological defence in a prey species is indirectly strengthened by predators via cascading predator effects on resource availability. This potentially represents an important mechanism that promotes prey persistence in the presence of predators.
许多被捕食者会在直接受到捕食线索的刺激时产生防御机制。然而，捕食者也可以通过增加猎物资源可利用性的间接机制，例如营养级联，来增强猎物的防御能力。我们评估了这些直接和间接影响对新西兰海胆机械强度的相对影响。我们测量了海胆测试（骨骼）在以下两种情况下的抗压能力：（i）两个海洋保护区，那里海胆的捕食者相对常见，并引发了营养级联，为幸存的海胆提供了丰富的食物，形式是巨藻；（ii）两个相邻的捕捞区，那里捕食者和巨藻很少见。在有大量捕食者和食物的受保护的岩石礁上栖息的海胆比在附近的捕捞礁上的个体具有更高的抗压能力，在那里捕食者和食物相对较少。为期六个月的中观实验表明，尽管食物供应和捕食者线索都增加了抗压能力，但食物供应对抗压能力的积极影响更大。我们的研究结果证明了一种新的机制，即通过捕食者对资源可利用性的级联影响，间接增强了猎物物种中一种假定的形态防御。这可能代表了一种重要的机制，可以促进猎物在存在捕食者的情况下的生存。
