The addition of non-native species and loss of native species has modified the composition of communities globally. Although changes in β-diversity have been well documented, there is a need for studies incorporating multiple time periods, more than one dimension of biodiversity, and inclusion of nestedness and turnover components to understand the underlying mechanisms structuring community composition and assembly. Here, we examined temporal changes in functional dissimilarity of fish communities of the Laurentian Great Lakes and compared these changes to those of taxonomic dissimilarity by decade from 1870 to 2010. Jaccard-derived functional dissimilarity index was used to quantify changes in functional β-diversity within communities, between all possible pairs of communities, and using a multiple-site index among all communities. β-diversity was partitioned into components of nestedness and turnover, and changes were examined over time. Similar to patterns in taxonomic dissimilarity, each community functionally differentiated from the historical community of 1870, with Lake Superior changing the most (~24%) and Lake Ontario the least (~14%). Although communities have become taxonomically homogenized, functional β-diversity among all communities has increased over time, indicating functional differentiation. This is likely due to functional similarity between the communities being historically high (i.e. ~88% similar in 1870). The higher taxonomic relative to functional turnover indicates that the species being replaced between communities are functionally redundant, which could occur given the harsh environmental conditions of the region and/or as a result of the recent glacial history of the region. High functional nestedness across communities reflects dispersal limitations, with smaller communities being functional subsets of large communities closer to source populations. The functional differentiation observed is likely due to non-native species with functional traits unique to the region establishing or the loss of functionally redundant native species; however, it is important to note that patterns of homogenization were periodically observed through time. Our study demonstrates the possible factors regulating diversity in the Laurentian Great Lakes fish communities, that patterns of taxonomic and functional β-diversity are dynamic over time and vary in the magnitude and direction of change, and that taxonomic diversity should not be used to predict changes in functional diversity.

中文翻译：

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功能分化伴随着淡水鱼类群落的分类同质化

非本地物种的增加和本地物种的丧失改变了全球群落的组成。尽管 β 多样性的变化已被充分记录，但仍需要进行包含多个时间段、不止一个生物多样性维度以及包含嵌套和周转成分的研究，以了解构建群落组成和组装的潜在机制。在这里，我们检查了 Laurentian Great Lakes 鱼类群落功能差异的时间变化，并将这些变化与 1870 年至 2010 年十年间分类学差异的变化进行了比较。 Jaccard 衍生的功能差异指数用于量化内部功能 β 多样性的变化社区，在所有可能的社区对之间，并在所有社区之间使用多站点索引。β-多样性被划分为嵌套和周转的组成部分，并随着时间的推移检查变化。类似于分类学差异的模式，每个群落在功能上都与 1870 年的历史群落不同，苏必利尔湖变化最大（~24%），安大略湖变化最小（~14%）。尽管群落在分类上已经变得同质化，但所有群落之间的功能 β 多样性随着时间的推移而增加，表明功能分化。这可能是由于社区之间的功能相似性在历史上很高（即 1870 年的相似度约为 88%）。较高的分类相对于功能周转率表明在群落之间被替换的物种在功能上是多余的，鉴于该地区恶劣的环境条件和/或该地区最近的冰川历史，这种情况可能会发生。社区之间的高功能嵌套反映了分散限制，较小的社区是更接近源种群的大型社区的功能子集。观察到的功能分化可能是由于具有该地区独特功能特征的非本地物种的建立或功能冗余的本地物种的丧失；然而，重要的是要注意随着时间的推移会定期观察到同质化模式。我们的研究证明了调节劳伦大湖鱼类群落多样性的可能因素，分类学和功能性 β 多样性的模式随着时间的推移是动态的，并且在变化的幅度和方向上有所不同，