Department of Ecology & Evolution, University of Chicago, 1101 E. 57th Chicago, IL, 60637, USA.
Computation Institute, University of Chicago, 5735, S. Ellis Ave, Chicago IL 60637, USA.
Ecol Lett. 2018 Mar;21(3):324-334. doi: 10.1111/ele.12912. Epub 2018 Jan 29.
Ecological networks that exhibit stable dynamics should theoretically persist longer than those that fluctuate wildly. Thus, network structures which are over-represented in natural systems are often hypothesised to be either a cause or consequence of ecological stability. Rarely considered, however, is that these network structures can also be by-products of the processes that determine how new species attempt to join the community. Using a simulation approach in tandem with key results from random matrix theory, we illustrate how historical assembly mechanisms alter the structure of ecological networks. We demonstrate that different community assembly scenarios can lead to the emergence of structures that are often interpreted as evidence of 'selection for stability'. However, by controlling for the underlying selection pressures, we show that these assembly artefacts-or spandrels-are completely unrelated to stability or selection, and are instead by-products of how new species are introduced into the system. We propose that these network-assembly spandrels are critically overlooked aspects of network theory and stability analysis, and we illustrate how a failure to adequately account for historical assembly can lead to incorrect inference about the causes and consequences of ecological stability.
理论上，表现出稳定动态的生态网络应该比那些波动剧烈的网络持续时间更长。因此，在自然系统中过度表现的网络结构通常被假设为生态稳定性的原因或结果。然而，很少有人考虑到这些网络结构也可能是决定新物种如何试图加入群落的过程的副产品。我们使用模拟方法，并结合随机矩阵理论的关键结果，说明了历史组装机制如何改变生态网络的结构。我们证明，不同的群落组装场景可能导致出现通常被解释为“选择稳定性”证据的结构。然而，通过控制潜在的选择压力，我们表明这些组装假象——或者说是支系——与稳定性或选择完全无关，而是新物种引入系统的方式的副产品。我们提出，这些网络组装支系是网络理论和稳定性分析中被严重忽视的方面，我们说明了未能充分考虑历史组装会如何导致对生态稳定性的原因和后果的错误推断。
