Data from: Joint evolution of differential seed dispersal and self-fertilization

Differential seed dispersal, in which selfed and outcrossed seeds possess different dispersal propensities, represents a potentially important individual-level association. A variety of traits can mediate differential seed dispersal, including inflorescence and seed size variation. However, how natural selection shapes such associations is poorly known. Here, we developed theoretical models for the evolution of mating system and differential seed dispersal in metapopulations, incorporating heterogeneous pollination, dispersal cost, cost of outcrossing, and environment-dependent inbreeding depression. We considered three models. In the “fixed dispersal model,” only selfing rate is allowed to evolve. In the “fixed selfing model,” in which selfing is fixed but differential seed dispersal can evolve, we showed that natural selection favours a higher, equal, or lower dispersal rate for selfed seeds to that for outcrossed seeds. However, in the “joint evolution model” in which selfing and dispersal can evolve together, evolution necessarily leads to higher or equal dispersal rate for selfed seeds compared to that for outcrossed. Further comparison revealed that outcrossed seed dispersal is selected against by the evolution of mixed mating or selfing, whereas the evolution of selfed seed dispersal undergoes independent processes. We discuss the adaptive significance and constraints for mating system/dispersal association.

差异化种子扩散（Differential seed dispersal）指自交种子与异交种子具备不同扩散倾向的现象，是一类潜在的重要个体水平关联。诸多性状可介导差异化种子扩散，包括花序与种子大小的变异。然而，当前学界对自然选择如何塑造这类关联仍知之甚少。本研究针对集合种群（metapopulations）中交配系统与差异化种子扩散的进化问题构建了理论模型，整合了异质授粉、扩散成本、异交成本以及环境依赖型近交衰退等要素。我们设置了三类模型：在"固定扩散模型"中，仅允许自交率发生进化；在"固定自交模型"中，自交率固定但差异化种子扩散可进化，研究显示自然选择会青睐自交种子相较于异交种子更高、相等或更低的扩散速率；而在"联合进化模型"中，自交率与扩散速率可共同进化，进化结果必然使自交种子的扩散速率高于或等于异交种子。进一步对比分析表明，混合交配或自交的进化会对异交种子的扩散产生选择抑制，而自交种子扩散的进化则遵循独立的过程。最后，我们讨论了交配系统与扩散关联的适应意义及约束限制。