Abstract A recent global assessment of terrestrial alien true ferns (Polypodiophyta; hereafter alien ferns) showed that alien ferns have a high probability of becoming naturalised or invasive once introduced. We provide the first systematic assessment, based on field surveys, of the invasion status of this large taxon in South Africa. Thirteen species of alien ferns were recorded outside of cultivation and subsequently identified as invasive in South Africa. Surveys were focused in known hotspots of alien and native ferns, with invasion density peaking along the eastern coastal belt of South Africa. Within the surveyed areas, alien ferns commonly occurred with other invaders, closer to water and often in indigenous forests. The species considered in this study generally occurred in similar habitat types across their native and globally introduced ranges (including South Africa). The potential spread of alien ferns in South Africa appears limited when compared to other major invaders, however, their common occurrence in indigenous forests highlights a concern for native, co-habiting fern species (in terms of competition). Our study provided regulatory insight for 12 previously unregulated alien fern species in South Africa. We propose that eradication remains feasible for Diplazium esculentum, Doodia caudata, Lygodium japonicum, Phlebodium aureum and Platycerium bifurcatum. A risk analysis for Sphaeropteris cooperi classified the species as high risk and comprised the first quantification of risk for any alien fern species (inclusive of aquatics) in South Africa. The information put forward in this study can be used to inform risk analyses for the remaining species in South Africa, as well as countries with similar habitats and climates. Furthermore, widely traded species need to be identified as candidates for future risk assessment since horticulture is an important introduction pathway for alien ferns globally.

中文翻译：

---

南非陆生外来蕨类植物（Polypodiophyta）入侵状况评估

摘要 最近对陆地外来真蕨类植物（Polypodiophyta；以下称为外来蕨类植物）的全球评估表明，外来蕨类植物一旦被引入，就极有可能被归化或入侵。我们根据实地调查对南非这一大型分类群的入侵状况进行了首次系统评估。有 13 种外来蕨类植物在种植之外被记录下来，随后被确定为在南非入侵。调查集中在已知的外来和本地蕨类植物热点地区，入侵密度在南非东部沿海地带达到顶峰。在所调查的区域内，外来蕨类植物通常与其他入侵者一起出现，靠近水源，通常在土著森林中。本研究中考虑的物种通常出现在其原生和全球引入范围（包括南非）的相似栖息地类型中。与其他主要入侵者相比，外来蕨类植物在南非的潜在传播似乎有限，然而，它们在土著森林中的普遍存在凸显了对本地共生蕨类植物物种的关注（就竞争而言）。我们的研究为南非 12 种以前不受管制的外来蕨类植物提供了监管见解。我们建议根除 Diplazium esculentum、Doodia caudata、Lygodium japonicum、Phlebodium aureum 和 Platycerium bifurcatum 仍然可行。Sphaeropteris cooperi 的风险分析将该物种归类为高风险，并首次量化了南非任何外来蕨类植物（包括水生植物）的风险。本研究中提出的信息可用于为南非剩余物种以及具有类似栖息地和气候的国家的风险分析提供信息。此外，需要将广泛交易的物种确定为未来风险评估的候选物种，因为园艺是全球外来蕨类植物的重要引入途径。