Dong Xiaoli, Lytle David A, Olden Julian D, Schriever Tiffany A, Muneepeerakul Rachata
School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.
Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America.
PLoS One. 2017 May 9;12(5):e0176949. doi: 10.1371/journal.pone.0176949. eCollection 2017.
Many ecosystems experience strong temporal variability in environmental conditions; yet, a clear picture of how niche and neutral processes operate to determine community assembly in temporally variable systems remains elusive. In this study, we constructed neutral metacommunity models to assess the relative importance of neutral processes in a spatially and temporally variable ecosystem. We analyzed macroinvertebrate community data spanning multiple seasons and years from 20 sites in a Sonoran Desert river network in Arizona. The model goodness-of-fit was used to infer the importance of neutral processes. Averaging over eight stream flow conditions across three years, we found that neutral processes were more important in perennial streams than in non-perennial streams (intermittent and ephemeral streams). Averaging across perennial and non-perennial streams, we found that neutral processes were more important during very high flow and in low flow periods; whereas, at very low flows, the relative importance of neutral processes varied greatly. These findings were robust to the choice of model parameter values. Our study suggested that the net effect of disturbance on the relative importance of niche and neutral processes in community assembly varies non-monotonically with the severity of disturbance. In contrast to the prevailing view that disturbance promotes niche processes, we found that neutral processes could become more important when the severity of disturbance is beyond a certain threshold such that all organisms are adversely affected regardless of their biological traits and strategies.
许多生态系统在环境条件方面经历着强烈的时间变异性；然而，关于生态位和中性过程如何在时间可变系统中运作以决定群落组装的清晰图景仍然难以捉摸。在本研究中，我们构建了中性集合群落模型，以评估中性过程在一个空间和时间可变的生态系统中的相对重要性。我们分析了来自亚利桑那州索诺兰沙漠河网20个地点跨越多个季节和年份的大型无脊椎动物群落数据。模型的拟合优度被用来推断中性过程的重要性。对三年间的八种水流条件进行平均后，我们发现中性过程在常年溪流中比在非常年溪流（间歇性和临时性溪流）中更重要。对常年溪流和非常年溪流进行平均后，我们发现中性过程在流量非常高和低流量时期更重要；而在流量非常低时，中性过程的相对重要性变化很大。这些发现对于模型参数值的选择具有稳健性。我们的研究表明，干扰对群落组装中生态位和中性过程相对重要性的净效应随干扰严重程度呈非单调变化。与普遍认为干扰促进生态位过程的观点相反，我们发现当中性过程的相对重要性在干扰严重程度超过一定阈值时可能变得更加重要，以至于所有生物无论其生物学特征和策略如何都会受到不利影响。
