Biological invasions are one of the most defining features of the Anthropocene. Most studies on biological invasions focus on the later stages of the invasion process, that is after species have already become naturalized. It is frequently overlooked, however, that patterns in origin, phylogeny and traits of naturalized alien species might largely reflect which species have been introduced in the first place. Here, we quantify and assess such introduction biases by analyzing 5317 plant species introduced for cultivation (i.e. primarily as ornamental garden plants) in the 10 countries composing Southern Africa. We show that this cultivated alien flora represents a non-random subset of the global flora and that this bias at the introduction stage largely contributes to patterns in geographic origin, phylogenetic composition and traits of the naturalized flora. For example, while species from Australasia are, compared to the global flora, disproportionally overrepresented in the naturalized cultivated flora of Southern Africa, this pattern is driven by their higher likelihood of introduction for cultivation. The same is true for the overrepresentation of free-standing woody species in the naturalized cultivated flora. The strong phylogenetic clustering of the naturalized cultivated flora is also, to a large extent, driven by introduction bias. Although functional traits explained little variation in naturalization success of cultivated plants, naturalization success was more likely for plants with intermediate seed mass and height and high specific leaf area. Thus, despite strong biases in which species have been introduced to Southern Africa, there are significant patterns in the species characteristics related to naturalization probability. Our quantification of introduction biases demonstrates that they are huge, and that accounting for it is important to avoid over- or under-emphasizing the characteristics of successfully naturalized alien plants.

中文翻译：

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南部非洲归化植物群的特征很大程度上反映了外来物种的非随机引入用于栽培

生物入侵是人类世最具决定性的特征之一。大多数关于生物入侵的研究都集中在入侵过程的后期阶段，即物种已经归化之后。然而，经常被忽视的是，归化的外来物种的起源、系统发育和特征的模式可能在很大程度上反映了首先引入的物种。在这里，我们通过分析在组成南部非洲的 10 个国家中引入用于栽培（即主要作为观赏园林植物）的 5317 种植物物种来量化和评估这种引入偏差。我们表明，这种栽培的外来植物群代表了全球植物群的一个非随机子集，并且这种引入阶段的偏差在很大程度上促成了地理起源模式，归化植物群的系统发育组成和特征。例如，虽然与全球植物群相比，澳大利亚的物种在南部非洲的归化栽培植物群中的比例过高，但这种模式是由它们被引入栽培的更高可能性所驱动的。归化栽培植物群中自立木本物种过多的情况也是如此。归化栽培植物群的强系统发育聚类在很大程度上也是由引入偏差驱动的。尽管功能性状解释了栽培植物归化成功率的微小差异，但具有中等种子质量和高度以及高比叶面积的植物更有可能归化成功。因此，尽管物种被引入南部非洲存在强烈偏见，与归化概率相关的物种特征存在显着模式。我们对引入偏差的量化表明它们是巨大的，并且考虑到这一点很重要，以避免过分或过分强调成功归化的外来植物的特征。