Charles Darwin posited two alternative hypotheses to explain the success of nonnative species based on their relatedness to natives: nonnative species that are closely related to native species could experience (1) higher invasion success because of an increased probability of habitat suitability (conferred by trait similarity) or (2) lower invasion success due to biotic interference, such as competition and limiting similarity. The paradox raised by the opposing predictions of these two hypotheses has been termed “Darwin’s naturalization conundrum” (DNC). Using plant communities measured repeatedly across an experimental fire gradient in an oak savanna (Minnesota, USA) over 31 yr, we evaluated the DNC by incorporating taxonomic, functional, and phylogenetic information. We used a “focal‐species” approach, in which the taxonomic, functional, and phylogenetic structure of species co‐occurring with a given nonnative (focal) species in local communities was quantified. We found three main results: first, nonnative species tended to co‐occur most with closely related natives, except at the extreme ends of the fire gradient (i.e., in communities with no fire and those subjected to high fire frequencies); second, with increasing fire frequency, nonnative species were functionally more similar to native species in recipient communities; third, functional similarity between co‐occurring nonnatives and natives was stable over time, but their phylogenetic similarity was not, suggesting that dynamic external forces (e.g., climate variability) influenced the phylogenetic relatedness of nonnatives to natives. Our results provide insights for understanding invasion dynamics across environmental gradients and highlight the importance of evaluating different dimensions of biodiversity in order to draw stronger inferences regarding species co‐occurrence at different spatial and temporal scales.

中文翻译：

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根据维管植物的分类，系统发育和功能维度测试达尔文的归化难题

查尔斯·达尔文（Charles Darwin）提出了两个可供选择的假设，以基于与本地物种的相关性来解释非本地物种的成功：与本地物种密切相关的非本地物种可能会遇到（1）更高的入侵成功率，因为​​栖息地适宜性的可能性增加（由特征相似性赋予） ）或（2）由于生物干扰（例如竞争和限制相似性）而降低入侵成功率。这两个假设的相反预测引起的悖论被称为“达尔文归化难题”（DNC）。使用在31年以上的橡树大草原（美国明尼苏达州）的实验火梯度上反复测量的植物群落，我们通过结合生物分类，功能和系统发育信息来评估DNC。我们使用了“焦点物种”方法，其中分类，功能，量化了与本地社区中给定的非本地（焦点）物种共存的物种的系统发育结构。我们发现了三个主要结果：首先，非本地物种往往与密切相关的本地人同时发生，除了在火灾梯度的极端处（即，在没有火灾的社区和遭受频繁火灾的社区中）；第二，随着着火频率的增加，外来物种在功能上与接收者社区的本土物种更相似；第三，同时出现的非本地人和本地人之间的功能相似性随着时间的推移是稳定的，但它们的系统相似性却不稳定，这表明动态外力（例如气候多变性）会影响非本地人与本地人的系统发育相关性。