Bower Luke M, Winemiller Kirk O
Department of Wildlife and Fisheries Sciences Texas A&M University College Station TX USA.
Ecol Evol. 2019 Nov 19;9(24):13862-13876. doi: 10.1002/ece3.5823. eCollection 2019 Dec.
Understanding of community assembly has been improved by phylogenetic and trait-based approaches, yet there is little consensus regarding the relative importance of alternative mechanisms and few studies have been done at large geographic and phylogenetic scales. Here, we use phylogenetic and trait dispersion approaches to determine the relative contribution of limiting similarity and environmental filtering to community assembly of stream fishes at an intercontinental scale. We sampled stream fishes from five zoogeographic regions. Analysis of traits associated with habitat use, feeding, or both resulted in more occurrences of trait underdispersion than overdispersion regardless of spatial scale or species pool. Our results suggest that environmental filtering and, to a lesser extent, species interactions were important mechanisms of community assembly for fishes inhabiting small, low-gradient streams in all five regions. However, a large proportion of the trait dispersion values were no different from random. This suggests that stochastic factors or opposing assembly mechanisms also influenced stream fish assemblages and their trait dispersion patterns. Local assemblages tended to have lower functional diversity in microhabitats with high water velocity, shallow water depth, and homogeneous substrates lacking structural complexity, lending support for the stress-dominance hypothesis. A high prevalence of functional underdispersion coupled with phylogenetic underdispersion could reflect phylogenetic niche conservatism and/or stabilizing selection. These findings imply that environmental filtering of stream fish assemblages is not only deterministic, but also influences assemblage structure in a fairly consistent manner worldwide.
系统发育和基于性状的方法增进了我们对群落构建的理解，然而，对于不同机制的相对重要性，目前尚未达成共识，并且在大地理尺度和系统发育尺度上开展的研究较少。在此，我们运用系统发育和性状离散方法，来确定在洲际尺度上，限制相似性和环境过滤对溪流鱼类群落构建的相对贡献。我们从五个动物地理区域采集了溪流鱼类样本。对与栖息地利用、摄食或两者相关的性状进行分析后发现，无论空间尺度或物种库如何，性状趋异的情况比性状过度离散更为常见。我们的研究结果表明，环境过滤以及在较小程度上的物种相互作用，是所有五个区域中栖息于小型、低梯度溪流的鱼类群落构建的重要机制。然而，很大一部分性状离散值与随机情况并无差异。这表明随机因素或相反的构建机制也影响了溪流鱼类群落及其性状离散模式。局部群落往往在水流速度高、水深浅且缺乏结构复杂性的均质底物的微生境中具有较低的功能多样性，这为胁迫优势假说提供了支持。功能趋异与系统发育趋异的高发生率可能反映了系统发育生态位保守性和/或稳定选择。这些发现意味着，溪流鱼类群落的环境过滤不仅具有确定性，而且在全球范围内以相当一致的方式影响群落结构。
