Department of Biology, Colorado State University, 251 W. Pitkin Street, Fort Collins, CO, 80523, USA.
Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, 80523, USA.
Oecologia. 2022 Jul;199(3):649-659. doi: 10.1007/s00442-022-05208-6. Epub 2022 Jul 14.
We sought to understand the role that water availability (expressed as an aridity index) plays in determining regional and global patterns of richness and evenness, and in turn how these water availability-diversity relationships may result in different richness-evenness relationships at regional and global scales. We examined relationships between water availability, richness and evenness for eight grassy biomes spanning broad water availability gradients on five continents. Our study found that relationships between richness and water availability switched from positive for drier (South Africa, Tibet and USA) vs. negative for wetter (India) biomes, though were not significant for the remaining biomes. In contrast, only the India biome showed a significant relationship between water availability and evenness, which was negative. Globally, the richness-water availability relationship was hump-shaped, however, not significant for evenness. At the regional scale, a positive richness-evenness relationship was found for grassy biomes in India and Inner Mongolia, China. In contrast, this relationship was weakly concave-up globally. These results suggest that different, independent factors are determining patterns of species richness and evenness in grassy biomes, resulting in differing richness-evenness relationships at regional and global scales. As a consequence, richness and evenness may respond very differently across spatial gradients to anthropogenic changes, such as climate change.
我们试图了解水分可利用性（用干旱指数来表示）在决定区域和全球丰富度和均匀度模式方面所起的作用，以及这些水分可利用性与多样性的关系如何导致在区域和全球尺度上产生不同的丰富度-均匀度关系。我们研究了跨越五个大陆广泛水分可利用性梯度的 8 个草地生物群落之间的水分可利用性、丰富度和均匀度之间的关系。我们的研究发现，水分可利用性与丰富度之间的关系在较干燥的生物群落（南非、西藏和美国）中为正相关，而在较湿润的生物群落（印度）中为负相关，但对于其余的生物群落则不显著。相比之下，只有印度生物群落的水分可利用性与均匀度之间存在显著的负相关关系。全球范围内，丰富度与水分可利用性之间的关系呈驼峰状，但对均匀度不显著。在区域尺度上，我们发现印度和中国内蒙古的草地生物群落中存在丰富度-均匀度的正相关关系。相比之下，这种关系在全球范围内呈弱凸形。这些结果表明，不同的、独立的因素决定了草地生物群落的物种丰富度和均匀度模式，导致在区域和全球尺度上产生不同的丰富度-均匀度关系。因此，丰富度和均匀度可能会对人为变化（如气候变化）的空间梯度产生非常不同的响应。
