Retesting a prediction of the River Continuum Concept: autochthonous versus allochthonous resources in the diets of invertebrates
Retesting a prediction of the River Continuum Concept: autochthonous versus allochthonous resources in the diets of invertebrates
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DOI：
10.1086/686302
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发表时间：
2016-03
影响因子：
1.8
通讯作者：
E. Rosi-Marshall;K. Vallis;C. Baxter;J. Davis
中科院分区：
文献类型：
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作者：
E. Rosi-Marshall;K. Vallis;C. Baxter;J. Davis
河流连续体概念（RCC）预测，温带森林流域河流的食物网（特别是无脊椎动物）应表现出一个纵向梯度，从对源头中陆地来源的有机物（例如季节性脱落的树叶）的依赖，到中游中的本土来源（例如藻类），再到较大河流中的悬浮物质。这一预测是通过对大型无脊椎动物群落的功能性摄食群体（FFG）进行纵向比较来评估的，但这种方法只能产生有关实际食物使用的间接证据。为了重新检验这一预测，我们研究了来自爱达荷州鲑鱼河的无脊椎动物饮食，方法是检查 1976 年最初的 RCC 研究中纵向采样地点的存档标本的肠道内容物，并在 2009 年从这些相同地点收集无脊椎动物。我们发现在大约 30 年的时间范围内饮食没有明显变化。无脊椎动物饮食中异地材料的重要性在沿纵向梯度的不同地点之间存在显着差异。正如预测的那样，它在二级源头处最高（平均为肠道内容物的 30-42%），并在最下游处纵向下降至 10% 至 20%。然而，第二级地点的无脊椎动物也消耗了大量的本土材料（35-45%），并且所有地点的饮食中都含有 35% 至 75% 的本土资源。最上游二级地点密度最高的粉碎机（Yoraperla）的肠道内容物根据季节由 52% 至 81% 硅藻组成，这说明了源头本地资源的重要性。我们的研究结果表明，仅测量 FFG 的变化而不检查大型无脊椎动物饮食中存在的实际食物资源可能会导致对食物网中大型无脊椎动物资源利用模式的错误推断。
The River Continuum Concept (RCC) predicts that food webs (and, in particular, invertebrates) of rivers in temperate, forested drainages should exhibit a longitudinal gradient from reliance on terrestrially derived organic matter (e.g., seasonally shed leaves) in the headwaters to autochthonous sources (e.g., algae) in the mid-orders, to suspended material in larger rivers. This prediction has been evaluated by longitudinal comparisons of macroinvertebrate communities in terms of functional feeding groups (FFGs), but such an approach yields only indirect evidence regarding actual food use. To retest this prediction, we investigated invertebrate diets from the Salmon River, Idaho, by examining the gut contents of archived specimens from the longitudinal set of sites sampled in the original 1976 RCC study and by collecting invertebrates from these same sites in 2009. We detected no apparent shifts in diets over the ∼30-y time span. The importance of allochthonous materials in invertebrate diets differed significantly among sites along the longitudinal gradient. As predicted, it was greatest at the 2nd-order headwater site (30–42% of gut contents, on average) and decreased longitudinally to 10 to 20% at the most downstream site. However, invertebrates at the 2nd-order site also consumed large percentages of autochthonous materials (35–45%), and diets contained from 35 to 75% autochthonous resources across all sites. The shredder (Yoraperla) with the highest density at the most upstream 2nd-order site had gut contents composed of 52 to 81% diatoms depending on season, illustrating the importance of autochthonous resources in the headwaters. Our findings show that measuring shifts in FFG alone without examining actual food resources present in macroinvertebrate diets may lead to erroneous inferences regarding patterns of resource use by macroinvertebrates in food webs.