Data from: Distance-dependent seedling mortality and long-term spacing dynamics in a neotropical forest community

Negative distance dependence (NDisD), or reduced recruitment near adult conspecifics, is thought to explain the astounding diversity of tropical forests. While many studies show greater mortality at near vs. far distances from adults, these studies do not seek to track changes in the peak seedling curve over time, thus limiting our ability to link NDisD to coexistence. Using census data collected over 12 years from central Panama in conjunction with spatial mark-connection functions, we show evidence for NDisD for many species, and find that the peak seedling curve shifts away from conspecific adults over time. We find wide variation in the strength of NDisD, which was correlated with seed size and canopy position, but other life-history traits showed no relationship with variation in NDisD mortality. Our results document shifts in peak seedling densities over time, thus providing evidence for the hypothesized spacing mechanism necessary for diversity maintenance in tropical forests.

负距离依赖（Negative distance dependence，NDisD），即成年同种个体周边的幼苗招募量降低，被认为可解释热带森林极高的物种多样性。尽管诸多研究均证实，相较于距成年个体较远的区域，近距区域的幼苗死亡率更高，但此类研究均未追踪幼苗密度峰值曲线随时间的动态变化，因而限制了我们将负距离依赖效应与物种共存机制关联起来的研究能力。本研究整合巴拿马中部地区长达12年的野外普查数据与空间标记连接函数（spatial mark-connection functions），在多个物种中验证了负距离依赖效应的存在，同时发现幼苗密度峰值曲线随时间推移逐渐远离同种成年个体。研究还发现，负距离依赖效应的强度存在显著的种间差异，且该差异与种子大小和冠层位置呈显著相关，但其余生活史特征与负距离依赖介导的死亡率差异并无关联。本研究结果记录了幼苗密度峰值随时间的动态变化，从而为热带森林物种多样性维持所需的假说性空间分隔机制提供了直接的实证支持。