Trait-mediated community assembly: distinguishing the signatures of biotic and abiotic filters

Conflicting hypotheses predict how traits mediate species establishment and community assembly. Traits of newly establishing individuals are predicted to converge, or be more similar to the resident, preexisting community, when the biotic or abiotic environment favors a single best phenotype, but are predicted to diverge when trait differences reduce competitive interactions. We tested these competing hypotheses using transplant seedlings in an old-field environment, and assessed the contribution of inter- and intra-specific transplant trait variation to community-level patterns. Using a soil moisture gradient and resident plant removals, we determined when traits of newly-establishing plants converge or diverge from the resident community by calculating community weighted mean traits for transplant and resident communities. We saw evidence of environmentally- and competitively-driven trait shifts that resulted in both trait convergence and divergence from the resident community, whose ...两类相互对立的假说分别阐释了性状如何调控物种定植与群落构建过程。当生物或非生物环境偏向单一最优表型时，新定植个体的性状被预测会与现存定居群落的性状趋同（即二者性状更为相似）；而当性状差异能够降低种间竞争强度时，新定植个体的性状则被预测会与现存群落产生趋异。本研究依托老弃耕地（old-field）生境中的移栽幼苗，对这两种对立假说进行了验证，并评估了种间与种内移栽植株的性状变异对群落水平格局的贡献。通过设置土壤湿度梯度与现存植株移除处理，并计算移栽群落与现存定居群落的群落加权平均性状（community weighted mean traits），本研究明确了新定植植物的性状何时会与现存群落发生趋同或趋异。研究观测到受环境与竞争共同驱动的性状转变证据，这类转变使得新定植植物的性状与现存群落同时出现了趋同与趋异现象，而现存群落的……