Department of Integrative Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
Ecol Lett. 2015 Oct;18(10):1012-20. doi: 10.1111/ele.12483. Epub 2015 Aug 6.
Animal migrations can link ecosystems across space. We discovered an aquatic insect that migrates between a river mainstem and its tributaries, and provides an important trophic subsidy for tributary predators. A mayfly, Ephemerella maculata, rears in a warm, sunlit productive river mainstem, then migrates as adults to cool, shaded unproductive tributaries where they oviposit and die. This migration tripled insect flux into a tributary for 1 month in summer. A manipulative field experiment showed that this E. maculata subsidy nearly tripled the growth of the young of the year steelhead trout (Oncorhynchus mykiss) in the recipient tributary over the summer months, and was more important than terrestrial invertebrate subsidies, which have been considered the primary food source for predators in small, forested creeks. By delivering food subsidies from productive but warming river mainstems to cool but food-limited tributaries, aquatic insect migrations could enhance resilience to cool-water predators in warming river networks.
动物迁徙可以将生态系统在空间上连接起来。我们发现一种水生昆虫在河流干流和支流之间迁徙，为支流中的捕食者提供了重要的营养物质。一种蜉蝣，Ephmerella maculata，在温暖、阳光充足的河流干流中生长，然后作为成虫迁徙到凉爽、阴凉、无生产力的支流中产卵并死亡。这种迁徙使夏季一个月内进入支流的昆虫数量增加了两倍。一项可操作的野外实验表明，这种 E. maculata 的补贴使接收支流中当年的幼年虹鳟鱼（Oncorhynchus mykiss）的生长速度在夏季的几个月里几乎增加了两倍，比陆地无脊椎动物补贴更为重要，因为后者一直被认为是小而森林覆盖的溪流中捕食者的主要食物来源。通过将营养物质从生产力较高但升温的河流干流输送到凉爽但食物有限的支流，水生昆虫的迁徙可以增强对变温水域中冷水性捕食者的适应能力。
