Department of Biology, Trent University, 1600 West Bank Drive, K9J 0G2, Peterborough, ON, Canada.
Department of Biology, Queen's University, 116 Barrie Street, K7L 3N6, Kingston, ON, Canada.
Heredity (Edinb). 2022 Jan;128(1):56-62. doi: 10.1038/s41437-021-00489-8. Epub 2021 Dec 16.
The transition to self-compatibility from self-incompatibility is often associated with high rates of self-fertilization, which can restrict gene flow among populations and cause reproductive isolation of self-compatible (SC) lineages. Secondary contact between SC and self-incompatible (SI) lineages might re-establish gene flow if SC lineages remain capable of outcrossing. By contrast, intrinsic features of SC plants that reinforce high rates of self-fertilization could maintain evolutionary divergence between lineages. Arabidopsis lyrata subsp. lyrata is characterized by multiple origins of self-compatibility and high rates of self-fertilization in SC-dominated populations. It is unclear whether these high rates of selfing by SC plants have intrinsic or extrinsic causes. We estimated outcrossing rates and examined patterns of pollinator movement for 38 SC and 40 SI maternal parents sampled from an admixed array of 1509 plants sourced from six SC and six SI populations grown under uniform density. Although plants from SI populations had higher outcrossing rates (mean t = 0.78 ± 0.05 SE) than plants from SC populations (mean t = 0.56 ± 0.06 SE), outcrossing rates among SC plants were substantially higher than previous estimates from natural populations. Patterns of pollinator movement appeared to contribute to lower outcrossing rates for SC plants; we estimated that 40% of floral visits were geitonogamous (between flowers of the same plant). The relatively high rates of outcrossing for SC plants under standardized conditions indicate that selfing rates in natural SC populations of A. lyrata are facultative and driven by extrinsic features of A. lyrata, including patterns of pollinator movement.
从自交不亲和到自交亲和的转变通常与高自交率相关，这可能限制种群间的基因流动，并导致自交亲和（SC）谱系的生殖隔离。如果 SC 谱系仍然能够异交，SC 和自交不亲和（SI）谱系之间的二次接触可能会重新建立基因流动。相比之下，如果 SC 植物具有加强高自交率的内在特征，则可能会维持谱系间的进化分歧。拟南芥 lyrata 亚种 lyrata 的特征是自交亲和的多次起源和 SC 主导种群中的高自交率。目前尚不清楚这些 SC 植物高自交率的原因是内在的还是外在的。我们从六个 SC 和六个 SI 种群中生长的 1509 株植物的混合群体中抽样了 38 株 SC 和 40 株 SI 母本，估计了异交率并检查了传粉者的运动模式。尽管来自 SI 种群的植物的异交率（均值 t=0.78±0.05 SE）高于来自 SC 种群的植物（均值 t=0.56±0.06 SE），但 SC 植物的异交率远高于以前在自然种群中的估计值。传粉者运动模式似乎导致 SC 植物的异交率降低；我们估计，40%的花朵访问是自花授粉（同一植株的花朵之间）。在标准化条件下，SC 植物的相对较高的异交率表明，A. lyrata 自然 SC 种群中的自交率是兼性的，并且受到 A. lyrata 的外在特征的驱动，包括传粉者运动模式。
