Data from: Fitness consequences of occasional outcrossing in a functionally asexual plant (Oenothera biennis)

Many clonal organisms occasionally outcross, but the long-term consequences of such infrequent events are often unknown. During five years, representing three to five plant generations, we followed 16 experimental field populations of the forb, Oenothera biennis, originally planted with the same 18 original genotypes. Oenothera biennis usually self-fertilizes, which due to its genetic system (Permanent Translocation Heterozygosity), results in seeds that are clones of the maternal plant. However, rare outcrossing produces genetically novel offspring (but without recombination or increased heterozygosity). We sought to understand whether novel genotypes produced through natural outcrossing had greater fecundity or different multigenerational dynamics compared to our original genotypes. We further assessed whether any differences in fitness or abundances through time between original and novel genotypes were exaggerated in the presence versus absence of insect herbivores. Over the course of the experiment, we genotyped >12,500 plants using microsatellite DNA markers to identify and track the frequency of specific genotypes and estimated fecundity on a subset (>3000) of plants. The effective outcrossing rate was 7.3% in the first year and ultimately 50% of the plants were of outcrossed origin by the final year of the experiment. Lifetime fruit production per plant was on average 32% higher across all novel genotypes produced via outcrossing compared to the original genotypes, and this fecundity advantage was significantly enhanced in populations lacking herbivores. Among 43 novel genotypes that were abundant enough to phenotype with replication, plants produced nearly 30% more fruits than the average of their specific two parental genotypes, and marginally more fruits (8%) than their most fecund parent. Mean per capita fecundity of novel genotypes predicted their relative frequencies at the end of the experiment. Novel genotypes increased more dramatically in herbivore-present compared to suppressed populations (45% vs. 27% of all plants), countering the increased competition from dandelions (Taraxacum officinale) that resulted from herbivore suppression. Increased interspecific competition likely also lead to the lower realized fitness of novel versus original genotypes in herbivore-suppressed populations. These results demonstrate that rare outcrossing and the generation of novel genotypes can create high-fecundity progeny, with the biotic environment influencing the dynamical outcome of such advantages.许多克隆生物（clonal organisms）偶尔会发生异交（outcrossing），但这类罕见事件的长期后果往往尚不明确。本研究针对非禾本科草本植物（forb）月见草（Oenothera biennis）的16个实验田间种群开展了为期5年、涵盖3至5个植物世代的跟踪调查，这些种群最初均由相同的18个原始基因型定植。月见草通常进行自交，因其自身的永久易位杂合性（Permanent Translocation Heterozygosity）遗传系统，其产生的种子为母本的克隆个体。而罕见的异交事件则会产生遗传上全新的后代（但未发生基因重组，也未提升杂合性）。本研究旨在探究两个核心问题：其一，通过自然异交产生的新颖基因型，其繁殖力是否高于原始基因型，或是表现出不同的多代种群动态？其二，在存在与缺失昆虫植食者的条件下，原始基因型与新颖基因型在适合度或种群丰度随时间变化的差异是否会被放大？实验期间，我们利用微卫星DNA标记（microsatellite DNA markers）对超过12500株植物进行基因分型，以识别并追踪特定基因型的种群频率；同时对其中超过3000株植物的繁殖力进行了量化估算。结果显示，实验第一年的有效异交率为7.3%，最终在实验末期，有50%的植株为异交起源。与原始基因型相比，所有通过异交产生的新颖基因型的单株终身结实量平均提升32%，且该繁殖力优势在无植食者的种群中显著增强。在43个丰度足够高、可进行重复表型观测的新颖基因型中，这些植株的单株结实量较其双亲的平均水平高出近30%，较繁殖力最高的亲本仅略低8%。新颖基因型的单株平均繁殖力可准确预测其在实验末期的相对种群频率。在存在植食者的种群中，新颖基因型的占比增长更为显著（分别为总植株数的45%与27%），抵消了植食动物抑制后由蒲公英（Taraxacum officinale）引发的种间竞争加剧问题。种间竞争加剧也可能是植食动物抑制种群中，新颖基因型实际适合度低于原始基因型的关键原因。本研究结果表明，罕见的异交事件与新颖基因型的产生可培育出高繁殖力的子代，而生物环境会显著影响这类优势带来的种群动态结局。