BACKGROUND AND AIMS Hybridisation is commonly assumed to aid invasions through adaptive introgression. In contrast, a recent theoretical model predicted that there can be non-adaptive demographic advantages from hybridisation and that the population consequences will depend on the breeding systems of the species and the extent to which subsequent generations are able to inter-breed and reproduce. We examined cross-fertilisation success and inheritance of breeding systems of two species in order to better assess the plausibility of the theoretical predictions. METHODS Reciprocal artificial crosses were made to produce F1, F2 and backcrosses between Cakile maritima (self-incompatible, SI) and Cakile edentula (self-compatible, SC) (Brassicaceae). Flowers were emasculated prior to anther dehiscence and pollen was introduced from donor plants to the recipient's stigma. Breeding system, pollen viability, pollen germination, pollen tube growth and reproductive output were then determined. The results were used to replace the assumptions made in the original population model and new simulations were made. KEY RESULTS The success rate with the SI species as the pollen recipient was lower than when it was the pollen donor, in quantitative agreement with the "SI x SC rule" of unilateral incompatibility. Similar outcomes were found in subsequent generations where fertile hybrids were produced but lower success rates were observed in crosses of SI pollen donors with SC pollen recipients. Much lower proportions of self-compatible hybrids were produced than expected from a single Mendelian allele. When incorporated into a population model, these results predicted an even faster rate of replacement of the self-compatible species by the self-incompatible species than previously reported. CONCLUSIONS Our study of these two species provides even clearer support for the feasibility of the non-adaptive hybridisation hypothesis whereby the colonisation of a self-incompatible species can be assisted by transient hybridisation with a congener. It also provides novel insight into reproductive biology beyond the F1 generation.

中文翻译：

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杂交后 Cakile（十字花科）育种系统的继承：对植物入侵的影响

背景和目的 杂交通常被认为通过适应性基因渗入来帮助入侵。相比之下，最近的一个理论模型预测，杂交可能会产生非适应性的人口优势，人口后果将取决于物种的繁殖系统以及后代能够杂交和繁殖的程度。我们检查了两个物种的育种系统的杂交成功和遗传，以更好地评估理论预测的合理性。方法 相互人工杂交以在 Cakile maritima（自交不亲和，SI）和 Cakile edentula（自交，SC）（十字花科）之间产生 F1、F2 和回交。花在花药开裂之前去势，花粉从供体植物引入受体的柱头。然后确定育种系统、花粉活力、花粉发芽、花粉管生长和生殖产量。结果被用来取代在原始人口模型中所做的假设，并进行了新的模拟。主要结果 SI 物种作为花粉接受者的成功率低于其作为花粉供体时的成功率，与单边不相容性的“SI x SC 规则”定量一致。在后代中发现了类似的结果，其中产生了可育的杂种，但在 SI 花粉供体与 SC 花粉受体的杂交中观察到较低的成功率。从单个孟德尔等位基因中产生的自相容杂种的比例比预期的要低得多。当纳入种群模型时，这些结果预测自相亲和物种被自相不相容物种取代的速度比以前报告的更快。结论我们对这两个物种的研究为非适应性杂交假说的可行性提供了更明确的支持，即通过与同源物的瞬时杂交可以辅助自交不相容物种的定殖。它还提供了对 F1 代以外的生殖生物学的新见解。结论我们对这两个物种的研究为非适应性杂交假说的可行性提供了更明确的支持，即通过与同源物的瞬时杂交可以辅助自交不相容物种的定殖。它还提供了对 F1 代以外的生殖生物学的新见解。结论我们对这两个物种的研究为非适应性杂交假说的可行性提供了更明确的支持，即通过与同源物的瞬时杂交可以辅助自交不相容物种的定殖。它还提供了对 F1 代以外的生殖生物学的新见解。