Gervais Jennifer A, Hunter Christine M, Anthony Robert G
Department of Forest, Range, and Wildlife Sciences, Utah State University, Logan, Utah 84322-5230, USA.
Ecol Appl. 2006 Apr;16(2):666-77. doi: 10.1890/1051-0761(2006)016[0666:ieopap]2.0.co;2.
We used population models to explore the effects of the organochlorine contaminant p,p'-DDE and fluctuations in vole availability on the population dynamics of Burrowing Owls (Athene cunicularia). Previous work indicated an interaction between low biomass of voles in the diet and moderate levels of p,p'-DDE in Burrowing Owl eggs that led to reproductive impairment. We constructed periodic and stochastic matrix models that incorporated three vole population states observed in the field: average, peak, and crash years. We modeled varying frequencies of vole crash years and a range of impairment of owl demographic rates in vole crash years. Vole availability had a greater impact on owl population growth rate than did reproductive impairment if vole populations peaked and crashed frequently. However, this difference disappeared as the frequency of vole crash years declined to once per decade. Fecundity, the demographic rate most affected by p,p'-DDE, had less impact on population growth rate than adult or juvenile survival. A life table response experiment of time-invariant matrices for average, peak, and crash vole conditions showed that low population growth under vole crash conditions was due to low adult and juvenile survival rates, whereas the extremely high population growth under vole peak conditions was due to increased fecundity. Our results suggest that even simple models can provide useful insights into complex ecological interactions. This is particularly valuable when temporal or spatial scales preclude manipulative experimental work in the field or laboratory.
我们使用种群模型来探究有机氯污染物p,p'-滴滴涕以及田鼠数量波动对穴小鸮（Athene cunicularia）种群动态的影响。先前的研究表明，穴小鸮卵中田鼠生物量低且p,p'-滴滴涕含量适中之间存在相互作用，这会导致繁殖能力受损。我们构建了周期性和随机性矩阵模型，纳入了在野外观察到的田鼠种群的三种状态：平均年份、高峰年份和低谷年份。我们模拟了田鼠低谷年份的不同频率以及田鼠低谷年份穴小鸮种群统计率的一系列受损情况。如果田鼠种群频繁达到峰值和低谷，田鼠的可获得性对穴小鸮种群增长率的影响要大于繁殖能力受损的影响。然而，随着田鼠低谷年份的频率降至每十年一次，这种差异消失了。受p,p'-滴滴涕影响最大的种群统计率——繁殖力，对种群增长率的影响小于成年或幼年个体的存活率。针对田鼠平均、高峰和低谷条件下的时不变矩阵进行的生命表响应实验表明，田鼠低谷条件下种群增长率低是由于成年和幼年个体存活率低，而田鼠高峰条件下种群增长率极高是由于繁殖力增加。我们的结果表明，即使是简单的模型也能为复杂的生态相互作用提供有用的见解。当时间或空间尺度排除了在野外或实验室进行操纵性实验工作时，这一点尤其有价值。
