Data from: Separating sources of density-dependent and density-independent establishment limitation in invading species

Successful colonization by invasive species depends on both the ability to disperse seeds to a site and an ability to establish once seeds have arrived. While seed and establishment limitation are known to jointly influence colonization, decomposing establishment limitation into density-dependent and density-independent components has remained challenging. Here, we couple theoretical models of recruitment with a multispecies invasion experiment conducted within a natural gradient of soil moisture and productivity to assess how variation in establishment limitation shapes outcomes for invasion. Recruitment was affected by both density-dependent and density-independent sources of establishment limitation in three of four species. Soil moisture stress and productivity both increased density-independent mortality in one species, whereas density-dependent mortality increased in locations with favourable soil moisture. Synthesis. Successful establishment of invading species can be limited by both density-dependent and density-independent mechanisms. In particular, the strength of density-independent limitation may depend on natural gradients in abiotic factors. The varying strengths of establishment limitation suggest that patterns of invasion are likely to be uneven both in space and in time. Understanding how intraspecific competitive constraints and density-independent limitation vary with abiotic gradients can assist with predicting when invasions are likely to occur, information that can be harnessed in the development of better methods for control.入侵物种的成功定殖，既依赖其向目标生境扩散种子的能力，也依赖种子抵达后成功建立种群的能力。尽管学界已知种子限制与建立限制共同影响定殖过程，但将建立限制拆解为密度依赖（density-dependent）与密度非依赖（density-independent）组分的研究仍颇具挑战。 本研究将种群补充理论模型与在土壤水分与生产力自然梯度下开展的多物种入侵实验相结合，以解析建立限制的变异如何塑造入侵结局。 在所研究的4个物种中，有3个物种的种群补充同时受到密度依赖与密度非依赖两类建立限制因素的调控。其中1个物种的土壤水分胁迫与生产力水平均会提升其密度非依赖死亡率，而在土壤水分条件适宜的生境中，该物种的密度依赖死亡率则会升高。 研究综合表明：入侵物种的成功建立同时受密度依赖与密度非依赖机制的限制。其中，密度非依赖限制的强度可能取决于非生物因子的自然梯度。建立限制强度的差异表明，入侵格局在空间与时间维度上均可能呈现非均匀性。明晰种内竞争约束与密度非依赖限制如何随非生物梯度发生变化，将有助于预测入侵事件的发生时机，相关信息可用于优化入侵防控方法的研发。