Assessing the phylogenetic dimension of Australian <i>Acacia</i> species introduced outside their native ranges

AbstractBiological invasion is a long process that starts with humans introducing intentionally (most of the time) species into a new environment to benefit from the ecosystem services that these species provide. Increasing evidence suggests that species providing ecosystem services might be phylogenetically closer than expected, but only a few studies actually demonstrate this. Also, recent studies indicate that naturalized and invasive species are two functionally distinct groups, but evidence that they are also two phylogenetically distinct groups is mixed. Using the set of Australian <i>Acacia</i> species known to have been introduced intentionally by humans to several parts of the world for the ecosystem services they provide, we first tested whether there is a phylogenetic pattern in the subset of introduced species. We found that species moved beyond Australia are phylogenetically more closely related than expected at random, suggesting that the ecosystem services that guide human-mediated introduction of these species into new areas (e.g. famine food, medicines, fuel, fodder, ornament) may be shared between closely related species. We also found that naturalized non-invasive and naturalized invasive species are closely related and both are not a phylogenetically random subset of introduced species based on mean phylogenetic distance, suggesting that naturalization and invasion processes may be phylogenetically mediated. Collectively, our study indicates that phylogeny might play different roles at different stages of the biological invasion process.摘要：生物入侵是一个漫长的过程，其开端为人类有意（多数情形下）将物种引入全新生境，以获取这些物种所能提供的生态系统服务。越来越多的证据表明，提供生态系统服务的物种在系统发育上可能比预期更为相近，但仅有少数研究实际证实了这一点。此外，近期研究指出归化物种与入侵物种是两类功能迥异的类群，但关于二者同样属于系统发育上独立类群的证据却并不一致。本研究以已知为获取其生态系统服务而被人类有意引入全球多地的澳大利亚金合欢属（*Acacia*）物种为研究对象，首先检验引入物种的子集是否存在系统发育模式。研究发现，被带出澳大利亚的物种在系统发育上的亲缘关系比随机预期更为紧密，这表明引导人类将这些物种人为引入新区域的生态系统服务（如赈灾食物、药物、燃料、饲料、观赏用途），可能在亲缘关系相近的物种间存在共有性。此外我们还发现，基于平均系统发育距离，非入侵性归化物种与入侵性归化物种亲缘关系紧密，且二者均不属于引入物种中系统发育上的随机子集，这表明归化与入侵过程可能受到系统发育的介导。综合来看，本研究表明系统发育在生物入侵过程的不同阶段可能发挥着不同的作用。