Granite outcrops are globally widespread habitat islands that harbour naturally fragmented areas of vegetation in ‘pockets’ of soil. These habitats are ideal for investigating the drivers of biogeographic patterns at different scales. However, beyond the tropics, understanding of the environmental drivers of community composition within and between these ‘island on islands’ is limited. In this study, we determined within‐ and between‐outcrop patterns of plant biodiversity in the Southwest Australian Floristic Region – a global biodiversity hotspot. We measured plant community composition of soil‐patches on nine granite outcrops. Outcrop floristic composition was mostly controlled by geographic location and outcrop topography (slope and aspect‐northness), whereas plant community diversity (richness, abundance, evenness and Simpson diversity) was strongly controlled by soil‐patch size, regardless of outcrop location or size. Outcrops with larger soil‐patches hosted greater plant diversity on those soil‐patches. Effective conservation of outcrops should focus on protecting the fragile soil communities on multiple rock outcrops at a regional scale to allow for the continuing persistence of extraordinary biodiversity in these regions.

中文翻译：

---

西南澳大利亚花区的花岗岩露头对植物群落的多尺度生物地理控制

花岗岩露头是全球分布广泛的生境岛，在“一小袋”土壤中藏有自然零散的植被区域。这些栖息地非常适合调查不同规模的生物地理格局的驱动因素。但是，除了热带地区以外，对这些“岛屿上的岛屿”内部和之间的社区构成的环境驱动因素的理解是有限的。在这项研究中，我们确定了西南澳大利亚花卉区（一个全球生物多样性热点）内植物生物多样性的露头模式和露头模式。我们在9个花岗岩露头上测量了土壤斑块的植物群落组成。露头植物区系组成主要受地理位置和露头地形（坡度和北坡度）控制，而植物群落多样性（丰富度，丰度，均匀性和辛普森多样性）均受土壤斑块大小的强烈控制，而与露头的位置或大小无关。土壤斑块较大的露头在这些土壤斑块上具有更大的植物多样性。有效地保护露头应该集中在区域规模上保护多处岩石露头上的脆弱土壤群落，以使这些地区的非凡生物多样性得以持续存在。