Department of Biology, St. Mary's College of Maryland, St. Mary's City, MD, USA.
PLoS One. 2012;7(9):e45490. doi: 10.1371/journal.pone.0045490. Epub 2012 Sep 18.
The successful establishment of invasive species has been shown to depend on aspects of the invaded community, such as gap characteristics. Biotic resistance may be particularly critical for stopping invaders at early life history stages, but new species can often invade following disturbances, which may create microsites with very different characteristics than are usually present. We examine the response of two invasive thistle species, Carduus nutans L. and C. acanthoides L., to three different microsite characteristics: disturbance type, size, and water availability. The two species initially responded differently to the type of disturbance: C. acanthoides had higher emergence and survival in plots with both above- and belowground disturbance, whereas C. nutans had better early performance in large microsites with above-ground disturbance only. Later in their life cycle, C. nutans performed better in plots that had been disturbed both above- and belowground, whereas C. acanthoides was largely unaffected by disturbance type. Increased emergence and survival, larger size and a higher proportion flowering were observed in larger gaps for both species throughout the life cycle. Watering had a negative impact on C. nutans emergence and fall survival and on C. acanthoides survival to the following summer. Overall, these results suggest that disturbance-generated microsite characteristics (disturbance type and size) may have large impacts on establishment of these two Carduus species, which in turn may persist well beyond the initial stages of growth. Studying invader responses to disturbance can help us to understand under what circumstances they are likely to establish and create persistent problems; avoiding or ameliorating such situations will have significant management benefits.
入侵物种的成功建立已被证明取决于入侵群落的各个方面，例如间隙特征。生物抗性对于阻止入侵物种在早期生命史阶段可能尤为关键，但新物种通常可以在干扰之后入侵，这可能会产生与通常存在的特征非常不同的小生境。我们研究了两种入侵蓟，C. nutans L. 和 C. acanthoides L. 对三种不同小生境特征的响应：干扰类型、大小和水分可用性。这两个物种最初对干扰类型的反应不同：C. acanthoides 在有地上和地下干扰的斑块中的出苗率和成活率较高，而 C. nutans 在只有地上干扰的大斑块中早期表现较好。在它们的生命周期后期，C. nutans 在地上和地下都受到干扰的斑块中表现较好，而 C. acanthoides 受干扰类型的影响不大。在整个生命周期中，两种物种在较大的间隙中都观察到更高的出苗率和成活率、更大的体型和更高的开花比例。浇水对 C. nutans 的出苗率和秋季成活率以及 C. acanthoides 对次年夏季的成活率都有负面影响。总体而言，这些结果表明，由干扰产生的小生境特征（干扰类型和大小）可能对这两个蓟属物种的建立有很大影响，这反过来又可能使其在初始生长阶段之后持续存在。研究入侵物种对干扰的响应可以帮助我们了解它们在什么情况下可能建立并产生持久的问题；避免或改善这种情况将具有重要的管理效益。
