Navarrete Sergio A, Manzur Tatiana
Estación Costera de Investigaciones Marinas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile.
Ecology. 2008 Jul;89(7):2005-18. doi: 10.1890/07-1231.1.
Investigating how food supply regulates the behavior and population structure of predators remains a central focus of population and community ecology. These responses will determine the strength of bottom-up processes through the food web, which can potentially lead to coupled top-down regulation of local communities. However, characterizing the bottom-up effects of prey is difficult in the case of generalist predators and particularly with predators that have large dispersal scales, attributes that characterize most marine top predators. Here we use long-term data on mussel, barnacle, limpet, and other adult prey abundance and recruitment at sites spread over 970 km to investigate individual- and population-level responses of the keystone intertidal sunstar Heliaster helianthus on the coast of Chile. Our results show that this generalist predator responds to changes in the supply of an apparently preferred prey, the competitively dominant mussel Perumytilus purpuratus. Individual-level parameters (diet composition, per capita prey consumption, predator size) positively responded to increased mussel abundance and recruitment, whereas population-level parameters (density, biomass, size structure) did not respond to bottom-up prey variation among sites separated by a few kilometers. No other intertidal prey elicited positive individual predator responses in this species, even though a large number of other prey species was always included in the diet. Moreover, examining predator-prey correlations at approximately 80, 160, and 200 km did not change this pattern, suggesting that positive prey feedback could occur over even larger spatial scales or as a geographically unstructured process. Thus individual-level responses were not transferred to population changes over the range of spatial scales examined here, highlighting the need to examine community regulation processes over multiple spatial scales.
研究食物供应如何调节捕食者的行为和种群结构仍然是种群与群落生态学的核心关注点。这些反应将决定通过食物网的自下而上过程的强度，这可能会潜在地导致对当地群落的自上而下的耦合调节。然而，对于广食性捕食者而言，尤其是对于具有大扩散尺度的捕食者（大多数海洋顶级捕食者的特征属性），描述猎物的自下而上效应是困难的。在这里，我们利用分布在970公里范围内的多个地点的贻贝、藤壶、帽贝及其他成年猎物丰度和补充量的长期数据，来研究智利海岸潮间带关键物种太阳海星的个体和种群水平反应。我们的结果表明，这种广食性捕食者对一种明显偏好的猎物——具有竞争优势的紫贻贝供应的变化做出反应。个体水平参数（食谱组成、人均猎物消耗量、捕食者大小）对贻贝丰度和补充量的增加呈正向反应，而种群水平参数（密度、生物量、大小结构）对相隔几公里的不同地点之间的自下而上的猎物变化没有反应。即使该物种的食谱中始终包含大量其他猎物物种，但没有其他潮间带猎物能引起该物种个体捕食者的正向反应。此外，在大约80、160和200公里处检查捕食者与猎物的相关性并没有改变这种模式，这表明正向猎物反馈可能在更大的空间尺度上发生，或者作为一个地理上无结构的过程发生。因此，在本文研究的空间尺度范围内，个体水平的反应并没有转化为种群变化，这突出了在多个空间尺度上研究群落调节过程的必要性。
