Department of Biology, University of Oulu, Oulu, Finland.
Oecologia. 2013 Apr;171(4):863-72. doi: 10.1007/s00442-012-2448-z. Epub 2012 Sep 11.
Different prey species can vary in their significance to a particular predator. In the simplest case, the total available density or biomass of a guild of several prey species might be most relevant to the predator, but behavioural and ecological traits of different prey species can alter the picture. We studied the population dynamics of a predator-prey setting in Finland by fitting first-order log-linear vector autoregressive models to long-term count data from active breeding sites of the northern goshawk (Accipiter gentilis; 1986-2009), and to three of its main prey species (1983-2010): hazel grouse (Bonasa bonasia), black grouse (Tetrao tetrix) and capercaillie (T. urogallus), which belong to the same forest grouse guild and show synchronous fluctuations. Our focus was on modelling the relative significance of prey species and estimating the tightness of predator-prey coupling in order to explain the observed population dynamics, simultaneously accounting for effects of density dependence, winter severity and spatial correlation. We established nine competing candidate models, where different combinations of grouse species affect goshawk dynamics with lags of 1-3 years. Effects of goshawk on grouse were investigated using one model for each grouse species. The most parsimonious model for goshawk indicated separate density effects of hazel grouse and black grouse, and different effects with lags of 1 and 3 years. Capercaillie showed no effects on goshawk populations, while the effect of goshawk on grouse was clearly negative only in capercaillie. Winter severity had significant adverse effects on goshawk and hazel grouse populations. In combination, large-scale goshawk-grouse population dynamics are coupled, but there are no clear mutual effects for any of the individual guild members. In a broader context, our study suggests that pooling data on closely related, synchronously fluctuating prey species can result in the loss of relevant information, rather than increased model parsimony.
不同的猎物物种对特定捕食者的重要性可能不同。在最简单的情况下，几种猎物物种的总可用密度或生物量可能与捕食者最相关，但不同猎物物种的行为和生态特征可以改变这种情况。我们通过对来自芬兰的北方松鸡（Accipiter gentilis；1986-2009 年）活跃繁殖地的长期计数数据以及三种主要猎物物种（1983-2010 年）：榛鸡（Bonasa bonasia）、黑琴鸡（Tetrao tetrix）和松鸡（T. urogallus）进行一阶对数线性向量自回归模型拟合，研究了芬兰的一个捕食者-猎物系统的种群动态。这些猎物物种属于同一森林松鸡类群，表现出同步波动。我们的重点是建模猎物物种的相对重要性，并估计捕食者-猎物耦合的紧密程度，以解释观察到的种群动态，同时考虑密度依赖性、冬季严重程度和空间相关性的影响。我们建立了九个具有竞争力的候选模型，其中不同的松鸡物种组合以 1-3 年的时滞影响松鸡的动态。我们使用每个松鸡物种的一个模型来研究松鸡对松鸡的影响。最简约的模型表明榛鸡和黑琴鸡对松鸡的密度影响不同，而且存在 1 年和 3 年的滞后影响。松鸡对松鸡没有影响，而松鸡对松鸡的影响仅在松鸡中明显为负。冬季严重程度对松鸡和榛鸡种群有显著的不利影响。综合来看，大规模的松鸡-松鸡种群动态是耦合的，但对于任何单个类群成员都没有明显的相互影响。从更广泛的角度来看，我们的研究表明，汇集密切相关、同步波动的猎物物种的数据可能会导致相关信息的丢失，而不是增加模型简约性。
