Data from: Inter-specific functional convergence and divergence and intra-specific negative density dependence underlie the seed-to-seedling transition in tropical trees

The seed-to-seedling transition constitutes a critical bottleneck in the life history of plants and represents a major determinant of species composition and abundance. However, we have surprisingly little knowledge regarding the forces driving this ontogenetic transition. Here we utilize information regarding organismal function to investigate the strength of intra- and interspecific negative density dependence during the seed-to-seedling transition in Puerto Rican tree species. Our analyses were implemented at individual sites and across an entire 16-ha forest plot, spanning 6 years. The functional richness of seedling assemblages was significantly lower than expected given the seed assemblages, but the functional evenness was significantly higher than expected, indicating the simultaneous importance of constraints on the overall phenotypic space and trait differences for successful transitions from seed to seedling. The results were consistent across years. Within species, we also found evidence for strong intraspecific negative density dependence, where the probability of transition was proportionally lower when in a site with high conspecific density. These results suggest that filtering of similar phenotypes across species and strong negative density dependence within and among species are simultaneously driving the structure and dynamics of tropical tree assemblages during this critical life-history transition.

种子至幼苗的阶段转变是植物生活史中的关键瓶颈，同时也是决定物种组成与种群丰度的核心调控因素。然而目前学界对驱动这一个体发育转变的核心机制仍知之甚少，这颇令人意外。本研究依托生物功能相关信息，针对波多黎各林木物种在种子至幼苗过渡阶段的种内与种间负密度依赖（intra- and interspecific negative density dependence）作用强度展开探究。本研究的分析分别在单个样地以及整片16公顷（ha）的森林样地中开展，研究周期横跨6年。幼苗集合群的功能丰富度显著低于基于种子集合群的预期值，但功能均匀度却显著高于预期——这表明整体表型空间的限制与性状差异，对种子向幼苗的成功转变均具有重要作用，二者的影响同时存在。上述研究结果在各年度间均保持一致。在物种内部，我们同样发现了强烈的种内负密度依赖证据：当样地内同种个体密度较高时，种子向幼苗的转变概率会成比例降低。上述结果表明，跨物种的相似表型过滤作用，以及物种内部和物种间强烈的负密度依赖，共同驱动了这一关键生活史过渡阶段中热带林木集合群的结构与动态变化。