Context

The habitat amount hypothesis (HAH) posits that local species richness is driven more by the amount of habitat in the surrounding landscape than by local patch size or habitat configuration. Habitat amount and configuration influence patch attributes, however, making it difficult to isolate these relative effects on local richness.

Objectives

We tested the HAH in an experimental system in which the amount (10–80%) and configuration (clumped vs. fragmented) of habitat (red clover) were adjusted independently within individual ‘landscapes’ (256-m² plots).

Methods

We used generalized linear models and model-selection criteria to evaluate how arthropod richness at two local scales (1 m² and 4 m²) varied as a function of the amount or fragmentation of habitat and of the size or shape of the local patch.

Results

Local richness was largely independent of the amount or configuration of habitat, as well as patch size or shape. Local richness was best modeled as a constant for all surveys but the first, in which fragmentation alone best explained variation in species richness, followed by patch shape (which is an indirect effect of fragmentation). Habitat amount had an overwhelmingly positive effect on arthropod richness at the landscape scale, however.

Conclusions

The HAH was not supported in this experimental system: local richness was generally unaffected by the amount of habitat in the surrounding landscape, whereas habitat configuration was sometimes important. Given that habitat amount affected landscape-wide richness, it may be that the HAH only applies at the ‘landscape scale’, at least in this system.

中文翻译：

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栖息地数量假说的实验检验揭示了栖息地面积的影响很小，但破碎化对当地物种丰富度的短暂或间接影响

语境

栖息地数量假设 (HAH) 假设当地物种丰富度更多地受周围景观中栖息地数量的驱动，而不是局部斑块大小或栖息地配置。然而，栖息地数量和配置会影响补丁属性，因此很难隔离这些对当地丰富度的相对影响。

目标

我们在一个实验系统中测试了 HAH，在该系统中，栖息地（红三叶草）的数量（10-80%）和配置（成块与分散）在各个“景观”（256 米²地块）内独立调整。

方法

我们使用广义线性模型和模型选择标准来评估节肢动物丰富度在两个局部尺度（1 m ²和 4 m ²）如何随栖息地的数量或破碎以及局部斑块的大小或形状而变化。

结果

当地的丰富度在很大程度上与栖息地的数量或配置以及斑块大小或形状无关。局部丰富度最好被建模为所有调查的常数，但第一个，其中单独的碎片化最好地解释了物种丰富度的变化，其次是斑块形状（碎片化的间接影响）。然而，栖息地数量对景观尺度上的节肢动物丰富度具有压倒性的积极影响。

结论

该实验系统不支持 HAH：当地丰富度通常不受周围景观中栖息地数量的影响，而栖息地配置有时很重要。鉴于栖息地数量影响了景观丰富度，HAH 可能仅适用于“景观尺度”，至少在这个系统中是这样。