Context

Habitat loss is widely recognized as the main driver of biodiversity loss around the globe, yet the effects of habitat fragmentation on biodiversity have been extensively debated in recent years.

Objectives

We used a robust dataset of medium and large-sized mammals to test (a) the Habitat Amount Hypothesis, which postulates that species richness can be mainly predicted by the total amount of habitat surrounding the sampling site, and (b) the effects of habitat fragmentation per se, which may be expected to be weak or mainly positive on species richness.

Methods

We compiled information on the occurrence of mammal species in 166 forest fragments across the Atlantic Forest. For each forest fragment, we extracted information on patch size, percentage of forest cover (a proxy for habitat amount), and edge density and number of fragments (fragmentation metrics). We related these metrics to mammalian richness considering separately for all species, forest-dependent species, disturbance-tolerant species, and different trophic guilds.

Results

All richness measures strongly declined with decreasing forest cover, yet were unaffected by patch size, number of patches and edge density. The only exception occurred with herbivore richness, which was affected by number of patches. However, we found fragmentation per se effects only for herbivore richness.

Conclusions

Our results show that mammal richness increased with habitat amount at the landscape, whereas habitat fragmentation per se had significant negative impacts on herbivores only. We therefore recommend maintaining highly forested landscapes and restoring severely deforested areas, being essential for ensuring high richness of mammals.

中文翻译：

---

测试生物多样性热点中大中型哺乳动物的栖息地数量假说和破碎效应

语境

生境的丧失被广泛认为是全球生物多样性丧失的主要驱动力，但是近年来生境破碎化对生物多样性的影响已经引起了广泛的争论。

目标

我们使用了一个强大的中型和大型哺乳动物数据集来测试（a）栖息地数量假说，该假说假设物种丰富度可以主要由采样点周围的栖息地总数来预测，以及（b）栖息地的影响本身的碎片化，可能对物种丰富度是弱的或主要是正面的。

方法

我们收集了有关横跨大西洋森林的166个森林碎片中哺乳动物物种发生情况的信息。对于每个森林碎片，我们提取了以下信息：斑块大小，森林覆盖率（代表栖息地数量）以及边缘密度和碎片数量（碎片度量）。我们将这些指标与哺乳动物的丰富度相关联，分别针对所有物种，与森林有关的物种，耐干扰的物种以及不同的营养协会进行考虑。

结果

随着森林覆盖率的降低，所有的丰度措施都大大降低，但不受斑块大小，斑块数量和边缘密度的影响。唯一的例外是草食动物的丰富度，其受斑块数量的影响。但是，我们发现碎片化本身仅对草食动物丰富有影响。

结论

我们的结果表明，哺乳动物的丰富度随景观中栖息地数量的增加而增加，而栖息地破碎本身仅对草食动物具有显着的负面影响。因此，我们建议保持森林茂密的景观并恢复森林砍伐严重的地区，这对于确保哺乳动物的高度丰富至关重要。