BackgroundPervasive introductions of non-native taxa are behind processes of homogenization of various types affecting the global flora and fauna. Chile’s freshwater ecosystems encompass a diverse and highly endemic fish fauna that might be sensitive to the introduction of non-native species, an ongoing process that started two centuries ago, but has to date received little attention. Using historical (native) and present-day (native and non-native) presence-absence data sets of compositional similarity, our goal was twofold: (1) evaluate patterns of taxonomic homogenization at various spatial scales and (2) identify clusters of widely versus narrowly distributed species to assess their relative role in compositional changes. We expect that non-native species with wide distributions might have a larger influence in taxonomic homogenization than those with narrow distributions.ResultsChile’s fish assemblages have become increasingly homogenized during the last two centuries when evaluating changes in compositional similarity among 201 watersheds (65.3 % of total comparisons showed homogenization) distributed among six defined biotic units. Taxonomic differentiation was significantly more prevalent than taxonomic homogenization within biotic units. Among biotic units, comparisons between historical and current compositional similarity were all significantly different. We identified one cluster of non-native fishes that were distributed across the entire five or six biotic units. This cluster included Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss) as the two most representative species. A second cluster we identified included fishes such that on average spanned only one or two biotic units.ConclusionsWe provide first evidence for an ongoing and large-scale process of taxonomic homogenization among Chile’s watersheds occurring at various scales. Our findings provide taxonomic and biogeographic baseline information for management plans and courses of action for conservation of native fishes, many of which are endemic. We also discuss management guidelines of non-native fishes in Chile. Baseline information of both native and non-native fish taxa might be applicable to other isolated regions elsewhere.

中文翻译：

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评估智利淡水鱼组合的分类同质化

背景非本地类群的普遍引入是影响全球动植物群的各种类型同质化过程的幕后推手。智利的淡水生态系统包含多样化和高度地方性的鱼类群，它们可能对引入非本地物种很敏感，这个过程在两个世纪前就开始了，但迄今为止很少受到关注。使用组成相似性的历史（本地）和当今（本地和非本地）存在-不存在数据集，我们的目标是双重的：（1）评估不同空间尺度的分类同质化模式和（2）识别广泛与狭窄分布的物种相比，以评估它们在组成变化中的相对作用。我们预计分布广泛的非本地物种可能比分布窄的物种对分类同质化产生更大的影响。 结果在过去两个世纪中，在评估 201 个流域（占总数的 65.3 %）组成相似性的变化时，智利的鱼类组合变得越来越同质化。比较显示同质化）分布在六个定义的生物单位中。生物单位内的分类分化明显比分类同质化更普遍。在生物单位中，历史和当前组成相似性之间的比较都有显着差异。我们确定了一组分布在整个五六个生物单元中的非本地鱼类。该集群包括褐鳟（Salmo trutta）和虹鳟（Oncorhynchus mykiss）作为两个最具代表性的物种。我们确定的第二个集群包括平均仅跨越一个或两个生物单位的鱼类。结论我们为智利不同规模的流域之间正在进行的大规模分类同质化过程提供了第一个证据。我们的研究结果为保护本地鱼类的管理计划和行动方案提供了分类学和生物地理基线信息，其中许多是地方性鱼类。我们还讨论了智利非本地鱼类的管理指南。本地和非本地鱼类分类群的基线信息可能适用于其他地方的其他孤立区域。我们确定的第二个集群包括平均仅跨越一个或两个生物单位的鱼类。结论我们为智利不同规模的流域之间正在进行的大规模分类同质化过程提供了第一个证据。我们的研究结果为保护本地鱼类的管理计划和行动方案提供了分类学和生物地理基线信息，其中许多是地方性鱼类。我们还讨论了智利非本地鱼类的管理指南。本地和非本地鱼类分类群的基线信息可能适用于其他地方的其他孤立区域。我们确定的第二个集群包括平均仅跨越一个或两个生物单位的鱼类。结论我们为智利不同规模的流域之间正在进行的大规模分类同质化过程提供了第一个证据。我们的研究结果为保护本地鱼类的管理计划和行动方案提供了分类学和生物地理基线信息，其中许多是地方性鱼类。我们还讨论了智利非本地鱼类的管理指南。本地和非本地鱼类分类群的基线信息可能适用于其他地方的其他孤立区域。我们的研究结果为保护本地鱼类的管理计划和行动方案提供了分类学和生物地理基线信息，其中许多是地方性鱼类。我们还讨论了智利非本地鱼类的管理指南。本地和非本地鱼类分类群的基线信息可能适用于其他地方的其他孤立区域。我们的研究结果为保护本地鱼类的管理计划和行动方案提供了分类学和生物地理基线信息，其中许多是地方性鱼类。我们还讨论了智利非本地鱼类的管理指南。本地和非本地鱼类分类群的基线信息可能适用于其他地方的其他孤立区域。