Jullien Margaux, Ronfort Joëlle, Gay Laurène
AGAP, INRAE, CIRAD, IRD, Montpellier SupAgro, Université de Montpellier, Montpellier, France.
Front Plant Sci. 2021 Feb 17;12:619154. doi: 10.3389/fpls.2021.619154. eCollection 2021.
Empirical studies on natural populations of revealed selfing rates higher than 80%, but never up to 100%. Similarly, several studies of predominantly selfing species show variability in the level of residual outcrossing between populations and also between temporal samples of the same population. However, these studies measure global selfing rates at the scale of the population and we do not know whether there is intra-population variation and how outcrossing events are distributed, between genotypes, plants, flowers, or seeds. Theoretical studies predict the maintenance of residual outcrossing in highly selfing species due to environmental (e.g., pollen biology) and/or genetic determinants and decompositions of the variation in outcrossing rate using experimental data can be very informative to test these hypotheses. Here, we focus on one natural population of in order to describe precisely its mating system. In particular, we investigated the determinants of the selfing rate by testing for seasonal variations (environmental determinism) and variations between genotypes (genetic determinism). We measured selfing rates in maternal progenies from plants collected widely across a natural population. For each plant, we collected pods from flowers produced at the beginning and at the end of the flowering season to test for a seasonal variation in the outcrossing rate. For each collected offspring, we also estimated the likelihood that it was issued from a self-fertilization event and assessed the genetic component of variation of this mating system measure. We found a significant, albeit small, increase in outcrossing rate in progenies collected at the end [ = 0.137 ( = 0.025)] compared to those collected at the beginning [ = 0.083 (0.016)] of the flowering season. A significant between genotypes variation in selfing rate was also detected, resulting in a heritability of 9% for the rate of residual outcrossing. Altogether, our work shows that despite a predominantly selfing reproductive mode, displays variation in residual outcrossing rate, and that this trait is likely under a complex determinism combining environmental and genetic factors. We discuss the evolutionary implications of our results for the population.
对[物种名称]自然种群的实证研究表明，自交率高于80%，但从未达到100%。同样，几项对主要自交物种的研究表明，种群之间以及同一种群的不同时间样本之间，残余异交水平存在差异。然而，这些研究是在种群尺度上测量总体自交率，我们不知道种群内部是否存在变异，以及异交事件在基因型、植株、花朵或种子之间是如何分布的。理论研究预测，由于环境因素（如花粉生物学）和/或遗传因素，高度自交物种中会维持残余异交现象，利用实验数据对异交率变异进行分解，对于检验这些假设可能非常有帮助。在这里，我们聚焦于[物种名称]的一个自然种群，以便精确描述其交配系统。特别是，我们通过测试季节性变化（环境决定因素）和基因型之间的差异（遗传决定因素）来研究自交率的决定因素。我们测量了从一个自然种群中广泛采集的植株所产生的母系后代的自交率。对于每株植物，我们在开花季节开始时和结束时采集花朵上的豆荚，以测试异交率的季节性变化。对于每个采集到的后代，我们还估计了其来自自花受精事件的可能性，并评估了这种交配系统测量值变异的遗传成分。我们发现，与开花季节开始时采集的后代相比[自交率 = 0.083（标准差 = 0.016）]，开花季节结束时采集的后代异交率显著增加，尽管增幅较小[自交率 = 0.137（标准差 = 0.025）]。我们还检测到自交率在基因型之间存在显著差异，导致残余异交率的遗传力为9%。总之，我们的研究表明，尽管[物种名称]主要采用自交繁殖模式，但其残余异交率存在变异，并且该性状可能受环境和遗传因素相结合的复杂决定机制影响。我们讨论了研究结果对该种群的进化意义。
