Data from: Source population characteristics affect heterosis following genetic rescue of fragmented plant populations

Understanding the relative importance of heterosis and outbreeding depression over multiple generations is a key question in evolutionary biology and is essential for identifying appropriate genetic sources for population and ecosystem restoration. Here we use 2455 experimental crosses between 12 population pairs of the rare perennial plant Rutidosis leptorrhynchoides (Asteraceae) to investigate the multi-generational (F1, F2, F3) fitness outcomes of inter-population hybridisation. We detected no evidence of outbreeding depression, with inter-population hybrids and backcrosses showing either similar fitness or significant heterosis for fitness components across the three generations. Variation in heterosis among population pairs was best explained by characteristics of the foreign source or home population, and was greatest when the source population was large, with high genetic diversity and low inbreeding and the home population was small and inbred. Our results indicate that the primary consideration for maximising progeny fitness following population augmentation or restoration is the use of seed from large, genetically diverse populations.探究多世代尺度下杂种优势（heterosis）与远交衰退（outbreeding depression）的相对重要性，是进化生物学领域的核心科学问题，同时也是筛选适宜遗传资源以开展种群与生态系统修复的关键前提。本研究以珍稀多年生植物长喙芮木菊（*Rutidosis leptorrhynchoides*，菊科Asteraceae）的12个种群对为研究对象，开展了2455组杂交实验，以此解析种群间杂交的多世代（F₁、F₂、F₃）适合度表现。研究未检测到远交衰退的相关证据：跨三个世代来看，种群间杂种与回交后代的适合度要么与亲本种群持平，要么在适合度组分上表现出显著的杂种优势。种群对间的杂种优势差异，可通过外来源种群或本土种群的特征得到最佳解释——当外来源种群规模较大、遗传多样性水平高且近交程度较低，而本土种群规模较小且存在近交现象时，杂种优势最为显著。本研究结果表明，若要通过种群增殖或生态修复实现后代适合度的最大化，首要考量应是选用源自大规模、遗传多样性丰富的种群的种子。