Data from: The benefits of interpopulation hybridization diminish with increasing divergence of small populations

Interpopulation hybridization can increase the viability of small populations suffering from inbreeding and genetic drift, but it can also result in outbreeding depression. The outcome of hybridization can depend on various factors, including the level of genetic divergence between the populations, and the number of source populations. Furthermore, the effects of hybridization can change between generations following the hybridization. We studied the effects of population divergence (low vs. high level of divergence) and the number of source populations (two vs. four source populations) on the viability of hybrid populations using experimental Drosophila littoralis populations. Population viability was measured for seven generations after hybridization as proportion of populations facing extinction and as per capita offspring production. Hybrid populations established at the low level of population divergence were more viable than the inbred source populations and had higher offspring production than the large control population. The positive effects of hybridization lasted for the seven generations. In contrast, at the high level of divergence the viability of the hybrid populations was not significantly different from the inbred source populations, and offspring production in the hybrid populations was lower than in the large control population. The number of source populations did not have a significant effect at either low or high level of population divergence. The study shows that the benefits of interpopulation hybridization may decrease with increasing divergence of the populations, even when the populations share identical environmental conditions. We discuss the possible genetic mechanisms explaining the results and address the implications for conservation of populations.

种群间杂交可提升遭受近交与遗传漂变的小型种群的存活力，但也可能引发远交衰退。杂交的结局取决于多种因素，包括种群间的遗传分化水平以及源种群的数量。此外，杂交效应在杂交后的各世代间会发生变化。本研究以实验性海滨果蝇（Drosophila littoralis）种群为材料，探究了种群分化水平（低分化vs. 高分化）与源种群数量（2个vs. 4个源种群）对杂交种群存活力的影响。我们在杂交后的连续7个世代中对种群存活力进行了测定，测定指标为面临灭绝的种群比例与单位个体后代产量。种群分化水平较低的杂交种群，其存活力优于近交源种群，且后代产量高于大型对照种群。杂交带来的积极效应持续了整整7个世代。与之相反，在种群分化水平较高的情况下，杂交种群的存活力与近交源种群并无显著差异，且其后代产量低于大型对照种群。无论种群分化水平高低，源种群数量均未产生显著影响。本研究表明，即便种群所处的环境条件完全一致，种群间杂交的益处可能会随种群分化程度的提升而减弱。我们探讨了可解释该研究结果的潜在遗传机制，并讨论了其对种群保护的启示。