Context

Movement of individuals and resources among habitat patches are key processes at the landscape scale. While these subsidies are primarily studied separately, coupled movement of species and resources, for example by animal vectors, may reinforce or dilute natural landscape heterogeneity, with consequences for the spatial distribution of biodiversity.

Objectives

We examine how transport of nutrients and seed by consumers’ feces corresponds to productivity gradients in the landscape, and whether herbivores and carnivores differ in the types of seeds they transport.

Methods

In California, we surveyed fecal deposition by vertebrates in 10 serpentine grassland fragments of varying productivities. We analyzed nitrogen content of feces before performing a germination assay to identify species transported therein.

Results

Herbivores deposited substantial amounts of nitrogen in serpentine grasslands via their feces, while carnivore scat was a high-quality but less predictable resource subsidy. Neither trophic group’s fecal deposition reinforced or diluted productivity gradients in the landscape. Rather, unproductive fragments received minimal nutrients, while more productive fragments had the chance of receiving higher resource inputs. Feces from both types of consumers contained viable seeds, but herbivores and carnivores transported non-overlapping subsets of plant species.

Conclusions

Consumers play different roles connecting plant communities in the landscape according to trophic level. Small herbivores are a continuous source of nutrient cycling, and their feces contains serpentine-adapted plant species, potentially serving as vectors for stepping-stone dispersal. While carnivores may be important vectors for long-distance seed dispersal, their movement patterns also make them more likely to deposit seeds in unsuitable environments.

中文翻译：

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动物将元生态系统中的植物物种和资源联系起来

语境

个人和资源在栖息地之间的移动是景观尺度上的关键过程。虽然这些补贴主要是单独研究的，但物种和资源的耦合移动（例如通过动物媒介传播）可能会增强或淡化自然景观的异质性，从而影响生物多样性的空间分布。

目标

我们研究了消费者粪便中养分和种子的运输如何与景观中的生产力梯度相对应，以及草食动物和食肉动物在运输的种子类型方面是否有所不同。

方法

在加利福尼亚，我们调查了脊椎动物在10个不同生产力的蛇形草地碎片中的粪便沉积情况。在进行发芽试验以鉴定其中运输的物种之前，我们分析了粪便中的氮含量。

结果

草食动物通过它们的粪便在蛇形草地中沉积了大量的氮，而食肉动物的粪便是一种高质量的资源，但其可预测性却较差。营养族的粪便沉积均未增强或降低景观中的生产力梯度。相反，非生产性碎片获得的营养最少，而生产性较高的碎片则有机会获得更多的资源投入。两种类型的消费者的粪便中都含有活种子，但食草动物和食肉动物运输的是植物物种的非重叠子集。

结论

消费者根据营养级别在连接景观中的植物群落方面扮演着不同的角色。小食草动物是养分循环的持续来源，它们的粪便中含有蛇纹石适应性植物，有可能作为垫脚石散布的载体。食肉动物可能是长距离传播种子的重要媒介，但它们的移动方式也使它们更有可能在不适当的环境中沉积种子。