Torres-Romero Erik Joaquín, Olalla-Tárraga Miguel Á
PhD Program in Ecology, Department of Life Sciences, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain.
Biodiversity and Conservation Unit, Department of Biology and Geology, Rey Juan Carlos University, Móstoles, 28933, Madrid, Spain.
J Anim Ecol. 2015 May;84(3):851-860. doi: 10.1111/1365-2656.12313. Epub 2014 Dec 16.
Different hypotheses (geographical, ecological, evolutionary or a combination of them) have been suggested to account for the spatial variation in species richness. However, the relative importance of environment and human impacts in explaining these patterns, either globally or at the biogeographical region level, remains largely unexplored. Here, we jointly evaluate how current environmental conditions and human impacts shape global and regional gradients of species richness in terrestrial mammals. We processed IUCN global distributional data for 3939 mammal species and a set of seven environmental and two human impact variables at a spatial resolution of 96.5 × 96.5 km. We used simple, multiple and partial regression techniques to evaluate environmental and human effects on species richness. Actual evapotranspiration (AET) is the main driver of mammal species richness globally. Together with our results at the biogeographical realm level, this lends strong support for the water-energy hypothesis (i.e. global diversity gradients are best explained by the interaction of water and energy, with a latitudinal shift in the relative importance of ambient energy vs. water availability as we move from the poles to the equator). While human effects on species richness are not easily detected at a global scale due to the large proportion of shared variance with the environment, these effects significantly emerge at the regional level. In the Nearctic, Palearctic and Oriental regions, the independent contribution of human impacts is almost as important as current environmental conditions in explaining richness patterns. The intersection of human impacts with climate drives the geographical variation in mammal species richness in the Palearctic, Nearctic and Oriental regions. Using a human accessibility variable, we show, for the first time, that the zones most accessible to humans are often those where we find lower mammal species richness.
人们提出了不同的假说（地理、生态、进化或它们的组合）来解释物种丰富度的空间变化。然而，在全球或生物地理区域层面，环境和人类影响在解释这些模式方面的相对重要性在很大程度上仍未得到探索。在这里，我们共同评估当前的环境条件和人类影响如何塑造陆地哺乳动物物种丰富度的全球和区域梯度。我们处理了3939种哺乳动物的世界自然保护联盟（IUCN）全球分布数据以及一组七个环境变量和两个人类影响变量，空间分辨率为96.5×96.5千米。我们使用简单、多元和偏回归技术来评估环境和人类对物种丰富度的影响。实际蒸散量（AET）是全球哺乳动物物种丰富度的主要驱动因素。结合我们在生物地理界层面的结果，这为水 - 能量假说提供了有力支持（即全球多样性梯度最好用水和能量的相互作用来解释，随着我们从极地向赤道移动，环境能量与水的可利用性的相对重要性会发生纬度变化）。虽然由于与环境共享的方差比例较大，在全球尺度上人类对物种丰富度的影响不易被检测到，但这些影响在区域层面显著显现。在新北区、古北区和东洋区，人类影响的独立贡献在解释丰富度模式方面几乎与当前环境条件同样重要。在古北区、新北区和东洋区，人类影响与气候的交叉作用驱动了哺乳动物物种丰富度的地理变化。通过使用人类可达性变量，我们首次表明，人类最容易到达的区域往往是哺乳动物物种丰富度较低的区域。
