Data from: Costs and benefits of non-random seed release for long distance dispersal in wind-dispersed plant species

The dispersal ability of plants is a major factor driving ecological responses to global change. In wind-dispersed plant species, non-random seed release in relation to wind speeds has been identified as a major determinant of dispersal distances. However, little information is available about the costs and benefits of non-random abscission and the consequences of timing for dispersal distances. We asked: 1) To what extent is non-random abscission able to promote long-distance dispersal and what is the effect of potentially increased pre-dispersal risk costs? 2) Which meteorological factors and respective timescales are important for maximizing dispersal? These questions were addressed by combining a mechanistic modelling approach and field data collection for herbaceous wind-dispersed species. Model optimization with a dynamic dispersal approach using measured hourly wind speed showed that plants can increase long-distance dispersal by developing a hard wind speed threshold below which no seeds are released. At the same time, increased risk costs limit the possibilities for dispersal distance gain and reduce the optimum level of the wind speed threshold, in our case (under representative Dutch meteorological conditions) to a threshold of 5-6 m s-1. The frequency and predictability (auto-correlation in time) of pre-dispersal seed-loss had a major impact on optimal non-random abscission functions and resulting dispersal distances. We observed a similar, but more gradual, bias towards higher wind speeds in six out of seven wind-dispersed species under natural conditions. This confirmed that non-random abscission exists in many species and that, under local Dutch meteorological conditions, abscission was biased towards winds exceeding 5-6 m s-1. We conclude that timing of seed release can vastly enhance dispersal distances in wind-dispersed species, but increased risk costs may greatly limit the benefits of selecting wind conditions for long-distance dispersal, leading to moderate seed abscission thresholds, depending on local meteorological conditions and disturbances.植物的扩散能力（dispersal ability）是驱动其响应全球变化的核心生态因子。对于风播植物物种（wind-dispersed plant species）而言，与风速相关的非随机种子释放（non-random seed release）已被证实是决定扩散距离（dispersal distances）的关键因素。然而，目前关于非随机脱落（abscission）的成本与收益，以及脱落时机对扩散距离的影响，相关研究仍较匮乏。 本研究提出两项核心科学问题：1）非随机脱落能够在多大程度上促进长距离扩散？扩散前风险成本的潜在增加会产生何种影响？2）哪些气象因子（meteorological factors）与对应的时间尺度（timescales）对最大化扩散距离至关重要？为解答上述问题，研究团队结合机制模型方法（mechanistic modelling approach）与草本风播植物物种（herbaceous wind-dispersed species）的野外数据采集工作开展了相关研究。 通过采用实测逐小时风速（hourly wind speed）构建动态扩散方法（dynamic dispersal approach）进行模型优化分析，结果显示：植物可通过设定硬风速阈值（hard wind speed threshold）——低于该阈值时不释放种子——来提升长距离扩散效率。与此同时，上升的风险成本会限制扩散距离的提升空间，并降低最优风速阈值的设定水平；在本次研究的典型荷兰气象条件下，该阈值被优化至5~6 m s⁻¹。扩散前种子损失（pre-dispersal seed-loss）的发生频率与可预测性（时间自相关（auto-correlation）），对最优非随机脱落函数与最终扩散距离均具有显著影响。 研究团队在自然条件下对7种风播植物中的6种进行观测，发现其种子脱落同样存在偏向更高风速的特征，且该特征呈现更为渐进的趋势。这一结果证实了非随机脱落现象广泛存在于诸多植物物种中，且在荷兰本地气象条件下，种子脱落偏向于风速超过5~6 m s⁻¹的天气过程。 综上，种子释放时机可大幅提升风播植物的扩散距离，但上升的风险成本会显著限制选择有利风况以实现长距离扩散的收益，最终导致适中的种子脱落阈值，且该阈值取决于当地气象条件与外界干扰（disturbances）。