Abstract Seed dispersal plays a central role in plant ecology and evolution, and understanding its variation is key to predicting species demography and range dynamics. However, dispersal is difficult to measure, and most modelling and field studies assume uniform dispersal within species, ignoring individual variation. Yet dispersal potential can differ strongly among individuals within species. More empirical data at the individual level are therefore needed to quantify the magnitude of intraspecific variation and its ecological underpinnings. We developed a wind dispersal trial to capture full individual seed dispersal distributions for 107 Arabidopsis thaliana genotypes originating across the species' European range. We used these data to (1) assess variation in seed dispersal patterns via dispersal kernel, (2) estimate dispersal kernel heritability, (3) identify how strong and widespread are the major phenotypic drivers of intraspecific variation in dispersal kernel, including (4) the relative contribution of intra‐individual versus inter‐individual phenotypic variation and (5) test whether spatial, demographic or environmental factors structure dispersal traits. Dispersal kernel properties, mean distance, skewness, kurtosis and standard deviation, varied significantly across genotypes and showed considerable heritability. These components were not uniformly controlled by the same set of traits. Mean distance, skewness and kurtosis that reflect aspects of average and longer distance dispersal were primarily driven by a few tightly linked traits, especially plant height and fecundity. In contrast, standard deviation (SD), which captures the variability in dispersal distance, was influenced by a broader and more complex set of predictors, including within‐individual variation in seed roundness and seed size. We found no clear geographic or demographic structure of dispersal kernel properties. However, SD, which is related to post‐dispersal sibling distance, was significantly associated with environmental unpredictability, suggesting it may represent an environmentally responsive and potentially adaptive strategy. Our findings reveal that, even within a single species and dispersal mode, dispersal varies substantially and is shaped by distinct trait dimensions. We highlight the need to account for intraspecific variation in seed dispersal potential and suggest that incorporating variation in kernel properties or the underlying trait complexity could improve predictions of species spread, persistence and adaptive capacity in changing environments. Read the free Plain Language Summary for this article on the Journal blog.
Utami et al. (Fri,) studied this question.