CRB: Food Web Analysis of Biodiversity: Application to Algal-based River Systems

研究人员提出了一种基于食物的程序来分析生物多样性问题。为了测试这种方法的有效性，他们将把它应用到加利福尼亚北部一个古老针叶林的河流食物网中。目前，这个地方是相对原始的，但外来食肉动物和食草动物（方鱼和牛蛙）预计将在几年内入侵。在入侵前的群落中，研究人员将研究在河流中占主导地位的初级生产者组合的大型藻类是如何调节包括优势脊椎动物和无脊椎食草动物在内的捕食者-猎物相互作用的。巨藻对生境选择、取食率、生长、存活、1)青蛙蝌蚪（Hyla regilla和Rana boylei）在存在和不存在食肉水生吊带蛇（Thamnophis couchi）的情况下的出现；2)在有和没有捕食性鱼类（蟑螂，Hesperoleucas symmetricus, Oncorhynchus mykiss）的情况下，对食性蠓幼虫（Pseudochironomus richardsoni）进行操作野外实验分析。这些研究的结果将使研究人员能够评估大型藻类在提供食物、避难所、或者是对这些优势的脊椎动物和无脊椎食草动物或它们的捕食者有利的微栖息地。将预测入侵后藻类或捕食者组合的变化将如何改变关键的食物网联系，然后在类似的河流中进行测试，这些河流中掠食性的方鱼和/或牛蛙已经到达。这些预测也将在入侵者确定后，在主要研究人员的主要研究地点进行测试。

The investigators propose a foodweb-based procedure for analysis of biodiversity problems. To test the validity of this approach, they will apply it to a river food web at a site within an old-growth conifer forest in northern California. At present, this site is relatively pristine, but invasion by exotic predators and herbivores (squawfish and bullfrogs) is anticipated within a few years. In the pre-invasion community, the researchers will investigate how macroalgae, which dominate primary producer assemblages in the river, mediate predator-prey interactions involving the dominant vertebrate and invertebrate grazers. The effects of macroalgae on habitat selection, feeding rates, growth, survival, and emergence of 1) frog tadpoles (Hyla regilla and Rana boylei) in the presence and absence of predatory aquatic garter snakes (Thamnophis couchi); and 2) algivorous midge larvae (Pseudochironomus richardsoni) in the presence and absence of predatory fishes (roach, Hesperoleucas symmetricus, and juvenile steelhead, Oncorhynchus mykiss) will be analyzed in manipulative field experiments. Results from these studies will allow the investigators to evaluate the relative importance of macroalgae in providing food, refuges, or thermally favorable microhabitats to these dominant vertebrate and invertebrate grazers, or to their predators. Predictions of how changes in algal or predator assemblages following invasions will alter critical food web linkages will be developed, then tested in similar river reaches where predatory squawfish and/or bullfrogs have already arrived. These predictions will also be tested at the primary study site of the principle investigators following the establishment of invaders.