Do stage-specific functional responses of consumers dampen the effects of subsidies on trophic cascades in streams?
Do stage-specific functional responses of consumers dampen the effects of subsidies on trophic cascades in streams?
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DOI：
10.1111/1365-2656.12192
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发表时间：
2014-07
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影响因子：
--
通讯作者：
Takuya Sato;Katsutoshi Watanabe
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文献类型：
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作者：
Takuya Sato;Katsutoshi Watanabe
资源补贴往往通过消费者对补贴的功能性反应来削弱受援国社区的营养级联。消费群体通常是阶段性的，在不同的阶段对补贴的反应可能不同，但关于这可能如何影响补贴对受援国系统中营养级联强度的影响，人们知之甚少。在这里，我们通过一个大规模的实地实验表明，接受补贴的消费者的阶段结构将抑制陆生无脊椎动物补贴对溪流中营养级联强度的影响。当陆地无脊椎动物的投入率较高时，无论大小鱼类阶段都将它们的食物转向陆地补贴，这削弱了溪流中的营养级联。然而，当陆地无脊椎动物的投入率处于中等水平时，陆地补贴并没有削弱营养级联。造成这种差异的原因可能是，在中等投入水平下，较小的鱼类阶段被竞争性地排除在大型鱼类阶段和主要以底栖无脊椎动物为食的补贴之外。虽然以往使用单鱼阶段的研究已清楚显示，相当于我们适度投入率的陆生无脊椎动物投入量削弱了溪流中的营养级联，但由于小鱼阶段可能不会在与大鱼阶段竞争的情况下转换食物以获得补贴，这种补贴效应可能被高估了。鉴于消费者阶段结构的普遍存在以及消费者阶段之间的相互作用，我们所看到的影响可能在自然界中是广泛的，需要未来的研究明确将消费者的阶段结构纳入社区生态。
Resource subsidies often weaken trophic cascades in recipient communities via consumers' functional response to the subsidies. Consumer populations are commonly stage-structured and may respond to the subsidies differently among the stages yet less is known about how this might impact the subsidy effects on the strength of trophic cascades in recipient systems. We show here, using a large-scale field experiment, that the stage structure of a recipient consumer would dampen the effects of terrestrial invertebrate subsidies on the strength of trophic cascade in streams. When a high input rate of the terrestrial invertebrates was available, both large and small fish stages switched their diet to the terrestrial subsidy, which weakened the trophic cascade in streams. However, when the input rate of the terrestrial invertebrates was at a moderate level, the terrestrial subsidy did not weaken the trophic cascade. This discrepancy was likely due to small fish stages being competitively excluded from feeding on the subsidy by larger stages of fish and primarily foraging on benthic invertebrates under the moderate input level. Although previous studies using single fish stages have clearly demonstrated that the terrestrial invertebrate input equivalent to our moderate input rate weakened the trophic cascade in streams, this subsidy effect might be overestimated given small fish stage may not switch their diet to the subsidy under competition with large fish stage. Given the ubiquity of consumer stage structure and interaction among consumer stages, the effects we saw might be widespread in nature, requiring future studies that explicitly involve consumer's stage structure into community ecology.