Olden Julian D, Poff N LeRoy
Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, 80523, USA.
Am Nat. 2003 Oct;162(4):442-60. doi: 10.1086/378212. Epub 2003 Oct 16.
The widespread replacement of native species with cosmopolitan, nonnative species is homogenizing the global fauna and flora. While the empirical study of biotic homogenization is substantial and growing, theoretical aspects have yet to be explored. Consequently, the breadth of possible ecological mechanisms that can shape current and future patterns and rates of homogenization remain largely unknown. Here, we develop a conceptual model that describes 14 potential scenarios by which species invasions and/or extinctions can lead to various trajectories of biotic homogenization (increased community similarity) or differentiation (decreased community similarity); we then use a simulation approach to explore the model's predictions. We found changes in community similarity to vary with the type and number of nonnative and native species, the historical degree of similarity among the communities, and, to a lesser degree, the richness of the recipient communities. Homogenization is greatest when similar species invade communities, causing either no extinction or differential extinction of native species. The model predictions are consistent with current empirical data for fish, bird, and plant communities and therefore may represent the dominant mechanisms of contemporary homogenization. We present a unifying model illustrating how the balance between invading and extinct species dictates the outcome of biotic homogenization. We conclude by discussing a number of critical but largely unrecognized issues that bear on the empirical study of biotic homogenization, including the importance of spatial scale, temporal scale, and data resolution. We argue that the study of biotic homogenization needs to be placed in a more mechanistic and predictive framework in order for studies to provide adequate guidance in conservation efforts to maintain regional distinctness of the global biota.
本土物种被世界性的非本土物种广泛取代，正在使全球动植物群落趋于同质化。虽然关于生物同质化的实证研究已经颇为丰富且不断增加，但理论方面仍有待探索。因此，可能塑造当前及未来同质化模式和速率的生态机制的广度在很大程度上仍不为人知。在此，我们构建了一个概念模型，该模型描述了物种入侵和/或灭绝可能导致生物同质化（群落相似性增加）或分化（群落相似性降低）的14种潜在情形；然后我们使用模拟方法来探究该模型的预测结果。我们发现群落相似性的变化随非本土和本土物种的类型及数量、群落之间历史上的相似程度以及在较小程度上随受纳群落的丰富度而变化。当相似物种入侵群落，导致本土物种不灭绝或不同程度地灭绝时，同质化最为显著。该模型的预测结果与鱼类、鸟类和植物群落的当前实证数据一致，因此可能代表了当代同质化的主要机制。我们提出了一个统一模型，阐明了入侵物种和灭绝物种之间的平衡如何决定生物同质化的结果。最后，我们讨论了一些与生物同质化实证研究相关的关键但大多未被认识到的问题，包括空间尺度、时间尺度和数据分辨率的重要性。我们认为，生物同质化研究需要置于一个更具机制性和预测性的框架中，以便研究能够为保护全球生物区系的区域独特性的保护工作提供充分指导。
