Data from: Global test of Eltonian niche conservatism of nonnative freshwater fish species between their native and introduced ranges

Despite growing evidence that biotic interactions limit the distribution of species and their potential redistribution under climate change, the recent surge of interest in niche conservatism has predominantly focused on the Grinellian (abiotic) niche, whereas few studies have attempted to quantify potential lability in the Eltonian (biotic or trophic) niche. Here, we test for conservatism in the Eltonian niche of 32 freshwater fish species between their introduced and native ranges from 435 populations across the globe. We used stable isotope data to quantify niche shifts along the horizontal (δ13C: indicating the origin of the resources consumed) and vertical (δ15N: describing the trophic position) dimensions of the isotopic niche, as well as shifts in overall isotopic niche breadth. Using an assemblage centroid standardized isotope vector analysis and controlling for phylogenetic relatedness among species, we demonstrated that introduced freshwater fishes exhibited flexibility in both resource use and trophic position that was beyond levels of natural variability observed in their native ranges. By contrast, niche breadth showed variability only within the limits recorded in native populations and varied independently from shifts in mean isotopic niche positions. Across all species and introduction histories, we found a consistent shift towards more balanced acquisition of resources with mixed origins and at intermediate trophic positions, suggesting a general mechanism by which fish species successfully establish into recipient communities. The mechanisms that promote or inhibit species from shifting their Eltonian niche remains unknown, but trophic flexibility is likely to contribute to both the success and the ecological impacts of invasive species and range shifts of native species under future global change.

尽管越来越多的证据表明生物相互作用会限制物种的分布及其在气候变化下的潜在再分布，但近期对生态位保守性（niche conservatism）的研究热潮主要集中在格氏生态位（Grinellian niche，即非生物生态位），而鲜有研究尝试量化埃氏生态位（Eltonian niche，即生物或营养生态位）的潜在可塑性。本研究针对全球435个种群的32种淡水鱼类，对比其引入分布区与原生分布区的埃氏生态位保守性。我们采用稳定同位素数据（stable isotope data），从水平维度（δ¹³C：指示所消耗资源的来源）与垂直维度（δ¹⁵N：描述营养级位置）量化同位素生态位（isotopic niche）的偏移，并分析整体同位素生态位宽度的变化。通过运用群落质心标准化同位素向量分析（assemblage centroid standardized isotope vector analysis），并控制物种间的系统发育亲缘关系（phylogenetic relatedness），本研究证实，引入的淡水鱼类在资源利用与营养级位置上均表现出超出其原生分布区自然变异水平的灵活性。与之形成对照的是，生态位宽度仅在原生种群记录的变异范围内存在波动，且与同位素生态位平均位置的偏移并无关联。综合所有物种与引入背景的数据，我们发现了一致的变化趋势：鱼类会转向获取来源混杂且处于中间营养级的资源，且资源获取更为均衡，这暗示了鱼类能够成功定殖于接收群落（recipient communities）的一种通用机制。目前尚不清楚哪些机制会促进或抑制物种改变其埃氏生态位，但营养级灵活性很可能有助于入侵物种（invasive species）的成功定殖及其生态影响，同时也可能影响未来全球变化背景下本土物种的分布区转移（range shifts）。