Apomixis, the asexual reproduction through seeds, occurs in over 40 plant families and avoids the hidden cost of sex. Apomictic plants are thought to have an advantage in sparse populations and when colonizing new areas but may have a disadvantage in changing environments because they propagate via fixed genotypes. In this study, we separated the influences of different genetic backgrounds (potentially reflecting local adaptation) from those of the mode of reproduction, i.e., sexual vs. apomictic, on nine fitness-related traits in Hieracium pilosella L. We aimed to test whether apomixis per se may provide a fitness advantage in different competitive environments in a common garden setting. To separate the effects of genetic background from those of reproductive mode, we generated five families of apomictic and sexual full siblings by crossing two paternal with four maternal parents. Under competition, apomictic plants showed reproductive assurance (probability of seeding, fertility), while offspring of sexual plants with the same genetic background had a higher germination rate. Sexual plants grew better (biomass) than apomictic plants in the presence of grass as a competitor but apomictic plants spread further vegetatively (maximum stolon length) when their competitors were sexual plants of the same species. Furthermore, genetic background as represented by the five full-sibling families influenced maximum stolon length, the number of seeds, and total fitness. Under competition with grass, genetic background influenced fecundity, the number of seeds, and germination rate. Our results suggest that both the mode of reproduction as well as the genetic background affect the success of H. pilosella in competitive environments. Total fitness, the most relevant trait for adaptation, was only affected by the genetic background. However, we also show for the first time that apomixis per se has effects on fitness-related traits that are not confounded by—and thus independent of—the genetic background.

中文翻译：

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无融合生殖和遗传背景影响竞争条件下生长的毛球菌的不同性状

无融合生殖是通过种子进行的无性繁殖，发生在 40 多个植物科中，避免了性的隐性成本。无融合生殖植物被认为在人口稀少和殖民新地区时具有优势，但在不断变化的环境中可能具有劣势，因为它们通过固定的基因型繁殖。在这项研究中，我们将不同遗传背景（可能反映局部适应）与繁殖方式的影响（即有性与无性生殖）对长毛菊九种适应性相关性状的影响区分开来。我们旨在测试是否无融合生殖本身可以在公共花园环境中的不同竞争环境中提供健身优势。为了将遗传背景的影响与生殖模式的影响区分开来，我们通过将两个父系与四个母系父母杂交，产生了五个无生殖和有性的完整兄弟姐妹家庭。在竞争中，无性生殖植物表现出生殖保证（播种概率、生育力），而具有相同遗传背景的有性植物的后代具有更高的发芽率。在草作为竞争者的情况下，有性植物比无性生殖植物生长得更好（生物量），但当它们的竞争对手是同一物种的有性植物时，无性生殖植物的无性繁殖更远（最大匍匐茎长度）。此外，以五个全兄弟家庭为代表的遗传背景影响最大匍匐茎长度、种子数量和总适应度。在与草的竞争下，遗传背景影响繁殖力、种子数量和发芽率。我们的研究结果表明，繁殖方式和遗传背景都会影响 H. pilosella 在竞争环境中的成功。总体适应度是与适应最相关的特征，仅受遗传背景的影响。然而，我们还首次表明，无融合生殖本身对与健康相关的性状有影响，这些性状不受遗传背景的影响，因此独立于遗传背景。