Data from: Is floral divergence sufficient to maintain species boundaries upon secondary contact in Mediterranean food-deceptive orchids?

Analysing the processes that determine whether species boundaries are maintained upon secondary contact may shed light on the early phase of speciation. In Anacamptis morio and A. longicornu, two Mediterranean orchid sister-species, we used molecular and morphological analyses, together with estimates of pollination success and experimental crosses, to assess whether floral isolation can shelter the species' genomes from genetic admixture upon secondary contact. We found substantial genetic and morphological homogenization in sympatric populations in combination with an apparent lack of postmating isolation. We further detected asymmetric introgression in the sympatric populations and an imbalance in cytotype representation, which may be due either to a difference in flowering phenology or else be a consequence of cytonuclear incompatibilities. Estimates of genetic clines for markers across sympatric zones revealed markers that significantly deviated from neutral expectations. We observed a significant correlation between spur length and reproductive success in sympatric populations, which may suggest that directional selection is the main cause of morphological differentiation in this species pair. Our results suggest that allopatric divergence has not led to the evolution of sufficient reproductive isolation to prevent genomic admixture upon secondary contact in this orchid species pair.解析调控物种边界在次生接触过程中得以维持的机制，可为物种形成的早期阶段提供关键视角。针对地中海兰科姊妹物种宽叶红门兰（Anacamptis morio）与长角红门兰（A. longicornu），本研究结合分子与形态学分析、传粉成功率评估及杂交实验，探究花部隔离能否在次生接触时保护物种基因组免受遗传混合。 研究发现，同域种群中存在显著的遗传与形态同质化现象，且未检测到明显的交配后生殖隔离。 此外，本研究在同域种群中检测到不对称基因渐渗现象，同时存在细胞型占比失衡的情况，该现象可能源于开花物候差异，亦或是核质不相容性所导致的结果。 对同域分布区的遗传标记开展遗传梯度分析，结果显示部分标记显著偏离中性预期。 我们在同域种群中观察到距长与生殖成功率间存在显著相关性，这表明定向选择是该物种种对形态分化的主要驱动因素。 本研究结果表明，异域分化并未演化出足够的生殖隔离，以阻止该兰物种种对在次生接触时发生基因组混合。