Environmental Science Program, Interdisciplinary Arts and Sciences, University of Washington, Tacoma, WA 98402, USA.
Risk Anal. 2010 Feb;30(2):175-82. doi: 10.1111/j.1539-6924.2009.01349.x. Epub 2010 Feb 2.
The use of surrogate species is an important tool in predicting the effects of management decisions or the establishment of protective measures for endangered/threatened species. While relying on a handful of model species to predict the fate of scores of distantly related target species has been criticized, a quantitative measure linking life history traits and population predictions has been sorely missing. We derive here a closed-form expression aimed at determining conditions under which sublethal effects of a toxicant on surrogate species population outcomes will reliably predict outcomes of target (listed) species. We develop a critical threshold in fecundity reduction above which the surrogate species outcomes indicate positive population growth, while the listed species is driven to extinction. Thus we have established a means of determining conditions under which we are prone to making a "Type II" error in assessing ecological risk using surrogate species. Finally, we use the derived expression and life history data to compare outcomes from four different commonly used fish surrogate species (round goby, fathead minnow, smallmouth bass, cutthroat trout) and their target listed species (Chinook and Coho salmon). We illustrate that all four surrogate species fail to predict population outcomes for the listed species in cases of as little as 15% fecundity reduction due to toxicant exposure. Furthermore, surrogate species reliability is a function of toxicant level, so that some species are reliable at some levels but not at others. We discuss the implications of these findings, and outline further analyses that occur as a natural extension of the criteria developed here.
替代物种的使用是预测管理决策或建立濒危/受威胁物种保护措施效果的重要工具。虽然依赖少数模型物种来预测数十种远缘目标物种的命运受到了批评，但缺乏将生活史特征与种群预测联系起来的定量方法。我们在这里推导出一个封闭形式的表达式，旨在确定在何种条件下，有毒物质对替代物种种群结果的亚致死效应将可靠地预测目标（列出）物种的结果。我们确定了一个临界生育力降低阈值，超过这个阈值，替代物种的结果表明种群呈正增长，而列出的物种则被推向灭绝。因此，我们已经建立了一种确定在何种条件下，我们倾向于使用替代物种评估生态风险时犯“第二类”错误的方法。最后，我们使用推导出的表达式和生活史数据比较了四种常用鱼类替代物种（圆鳍鱼、黑头呆鱼、小口黑鲈、虹鳟）及其目标列出物种（奇努克和银鲑）的结果。我们表明，在由于有毒物质暴露而导致生育力降低 15%的情况下，所有四种替代物种都无法预测列出物种的种群结果。此外，替代物种的可靠性是毒物水平的函数，因此某些物种在某些水平上是可靠的，但在其他水平上则不可靠。我们讨论了这些发现的意义，并概述了作为这里开发的标准的自然延伸而进行的进一步分析。
