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.

探明杂种优势（heterosis）与远交衰退（outbreeding depression）在多世代中的相对重要性，是进化生物学领域的核心科学问题之一，亦是确定种群与生态系统修复所需适宜遗传资源的必要前提。本研究以稀有多年生草本植物细喙菊（Rutidosis leptorrhynchoides，菊科）的12个种群对为研究对象，共计开展2455例实验杂交，以此探究种群间杂交的多世代（F1、F2、F3）适合度表现。研究未发现远交衰退的相关证据：在三个世代中，种群间杂种与回交（backcrosses）后代的适合度要么与亲本无显著差异，要么在适合度相关性状上表现出显著的杂种优势。不同种群对间的杂种优势差异，可通过外来源种群或本地种群的特征得到最佳解释：当外来源种群规模较大、遗传多样性高且近交（inbreeding）程度低，而本地种群规模较小且存在近交时，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最大化，首要考量应是选用来自大规模、高遗传多样性种群的种子。