Data from: Covariation in abscission force and terminal velocity of wind-borne sibling seeds alters long distance dispersal projections

1. Despite the fact that seeds are unlikely to be identical—even among siblings within a maternal individual—dispersal models typically use one mean trait value to represent the ability of an entire species to disperse. Previous work has shown that the environmental conditions under which individuals leave the maternal site strongly affect how far seeds will travel. However, less is known about how trait variation within individuals contributes to dispersal or how such variation might interact with abiotic factors. 2. Here, we develop the use of an ergometer in a novel application to investigate variation in seed traits, specifically the force required for seed abscission and seed terminal velocity, exhibited by seeds from different locations within maternal capitula of the invasive species Carduus nutans (Asteraceae). 3. We find that seeds from the center of capitula are significantly easier to liberate and have slower falling velocities than siblings found near the edge of capitula. When abscission force is positively correlated with terminal velocity, slowly falling, easily abscised seeds are projected to travel much further than the average seed on slow winds. 4. Our experimental and theoretical results, which together show that within-individual variation can strongly affect model projections of species dispersal, have important implications for our broader understanding of population spread rates, the spatial structure of populations, metapopulation connectivity, and gene flow in the landscape.

1. 尽管即便同一母株上的姊妹种子之间也几乎不可能完全一致，但扩散模型通常仅采用单一平均性状值来代表整个物种的扩散能力。已有研究表明，植株脱离母株位点时的环境条件会显著影响种子的传播距离。但目前学界对植株内部的性状变异如何影响种子扩散，以及这类变异与非生物因子的交互作用仍知之甚少。
2. 本研究将测力装置（ergometer）应用于全新的研究场景，以探究入侵物种垂花飞廉（Carduus nutans，菊科Asteraceae）的母株头状花序（capitula）不同位置所产种子的性状变异，具体聚焦于种子脱落（seed abscission）所需的作用力与种子终端速度（terminal velocity）两个指标。
3. 研究发现，头状花序中心位置的种子相较于边缘位置的姊妹种子，显著更易脱落且终端下落速度更慢。当脱落作用力与终端速度呈正相关时，在低风速环境中，易脱落且下落缓慢的种子的理论传播距离将远超种群平均水平。
4. 本研究的实验与理论结果共同表明，植株内部的性状变异可对物种扩散模型的预测结果产生显著影响，这一发现对于我们深入理解种群扩散速率、种群空间结构、集合种群（metapopulation）连通性以及景观中的基因流均具有重要意义。