ABSTRACT: Macroecological research over large latitudinal gradients can reveal broad-scale patterns that provide context for local-scale studies and insight into relevant scales of variation in community structure. Grazing by sea urchins is one of numerous physical and biotic factors that leads to geographic variation in community structure on rocky reefs worldwide. We describe patterns of abundance, distribution, and trophic interactions of urchins and their predators on subtidal rocky reefs across much of their range in the northeast Pacific Ocean. Surveys and tethering experiments were conducted between Point Conception, California, USA, and Bahía Asunción, Baja California Sur, México, including both fished areas and marine protected areas (MPAs). Variability in abundance was greatest at the smallest spatial scales (transects and sites) rather than the largest spatial scale (regions); however, we found correlative evidence of region-wide top-down control in which higher densities of predators (primarily spiny lobsters) led to increased abundances of kelp Macrocystis pyrifera. Similarly, urchin survival varied regionally, with survival rates increasing from south to north. The effect of MPAs was less clear: species abundances varied between individual MPAs, but there were no clear differences in urchin survival between MPAs and fished areas. Community structure of rocky reefs in this region varies substantially among sites and appears to be driven in some locations by predators and in others by factors that obscure the importance of trophic interactions. Our study provides empirical evidence of the variability in top-down forcing in these communities and cautions against making broad generalizations based on inferences from local-scale studies.

中文翻译：

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东北太平洋岩石礁上关键物种之间的分布，丰度和相互作用的生物地理变化

摘要：对较大纬度梯度的宏观生态学研究可以揭示广泛的模式，这些模式为地方尺度的研究和对社区结构变化的相关尺度的洞察提供了背景。海胆放牧是众多物理和生物因素之一，它导致全球岩礁社区结构的地理变异。我们描述了海胆及其捕食者在东北太平洋大部分地区潮下礁石上的丰度，分布和营养相互作用的模式。在美国加利福尼亚的Point Conception和墨西哥下加利福尼亚州的南下加利福尼亚州的巴伊亚亚松森（BahíaAsunción）之间进行了调查和系留实验，包括捕鱼区和海洋保护区（MPA）。在最小的空间尺度（样线和站点）而不是最大的空间尺度（区域），丰度的变化最大。但是，我们发现了从上至下控制范围的相关证据，其中较高密度的捕食者（主要是多刺龙虾）导致海藻丰度增加Macrocystis pyrifera。同样，海胆的生存率在各地也不同，生存率从南到北都在增加。MPA的影响尚不明确：各个MPA之间的物种丰富度各不相同，但MPA与渔区之间的野胆存活率没有明显差异。该地区岩石礁的群落结构在不同地点之间存在很大差异，在某些地方似乎是由掠食者驱动的，而在另一些地方则是由掩盖营养相互作用的重要性的因素驱动的。我们的研究提供了这些社区自上而下强迫的可变性的经验证据，并警告不要基于本地研究的推论做出广泛的概括。