Stark John D, Banks John E, Vargas Roger
Department of Entomology, Ecotoxicology Program, Washington State University, Puyallup, WA 98371, USA.
Proc Natl Acad Sci U S A. 2004 Jan 20;101(3):732-6. doi: 10.1073/pnas.0304903101. Epub 2004 Jan 12.
Measurements of toxicity based on individuals, such as the LC(50) (concentration that kills 50% of a population), and effects on reproduction are used extensively in determining ecological risk, in particular, for endangered or threatened species. An underlying assumption is that individual-based toxicity metrics for one species can be directly compared with that for another species. However, this assumption overlooks the fact that different species have different life-history strategies and variables, such as lifespan, time to first reproduction, and number of offspring produced over a lifetime. Using a simple model and laboratory-derived parameter values, we tested the impact of differences in life-history traits on predicted responses to stress. The model predicts the delay in population growth. We compared seven invertebrate species by imposing 50% chronic mortality, 50% reduction of offspring, and both of these effects. The model predicted substantial differences in population delay among all of the species. Furthermore, the intrinsic rate of increase of each population was negatively correlated with the delay in population growth; species with high intrinsic rates of increase were less susceptible to equal levels of stress than species with lower intrinsic rates of increase. These results suggest that the susceptibility of species to pollutants is more complicated than previously thought and that differences in life-history variables must be considered in analyses of population persistence for threatened and endangered species.
基于个体的毒性测量，如半数致死浓度（LC(50)，即杀死种群50%个体的浓度）以及对繁殖的影响，在确定生态风险时被广泛应用，尤其是针对濒危或受威胁物种。一个潜在的假设是，针对一个物种的基于个体的毒性指标可以直接与另一个物种的指标进行比较。然而，这一假设忽略了不同物种具有不同生活史策略和变量这一事实，比如寿命、首次繁殖时间以及一生中产生的后代数量。我们使用一个简单模型和实验室得出的参数值，测试了生活史特征差异对预测应激反应的影响。该模型预测种群增长的延迟。我们通过施加50%的慢性死亡率、50%的后代数量减少以及这两种影响来比较七种无脊椎动物物种。该模型预测所有物种在种群延迟方面存在显著差异。此外，每个种群的内禀增长率与种群增长延迟呈负相关；内禀增长率高的物种比内禀增长率低的物种对同等程度的应激更不敏感。这些结果表明，物种对污染物的敏感性比之前认为的更为复杂，并且在分析濒危和受威胁物种的种群持续性时必须考虑生活史变量的差异。
