Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland.
Zurich-Basel Plant Science Center, University of Zurich, ETH Zurich, University of Basel, Tannenstrasse 1, 8092, Zurich, Switzerland.
BMC Biol. 2021 Aug 28;19(1):177. doi: 10.1186/s12915-021-01117-x.
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.
无融合生殖，即通过种子进行的无性繁殖，发生在 40 多个植物科中，避免了性的隐藏成本。无融合生殖植物被认为在稀疏的种群和新地区的殖民化中具有优势，但在不断变化的环境中可能处于劣势，因为它们通过固定的基因型进行繁殖。在这项研究中，我们将不同的遗传背景（可能反映局部适应）的影响与繁殖方式（有性生殖与无融合生殖）的影响分开，以研究 Hieracium pilosella L. 的九个与适应度相关的特征。我们旨在测试在一个共同花园环境中，无融合生殖本身是否可以在不同的竞争环境中提供适应度优势。
为了将遗传背景的影响与生殖模式的影响分开，我们通过与四个母本杂交，由两个父本生成了五个无融合生殖和有性全同胞家系。在竞争下，无融合生殖植物表现出繁殖保证（结实概率、育性），而具有相同遗传背景的有性植物后代的发芽率更高。在有草作为竞争者的情况下，有性植物的生长状况（生物量）优于无融合生殖植物，但当同种的有性植物作为竞争者时，无融合生殖植物通过营养繁殖（最长匍匐茎）的方式扩散得更远。此外，以五个全同胞家系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，遗传背景影响了繁殖力、种子数量和发芽率。
我们的研究结果表明，繁殖方式以及遗传背景都会影响 H. pilosella 在竞争环境中的成功。总适应度是与适应最相关的特征，仅受遗传背景的影响。然而，我们也首次表明，无融合生殖本身对与适应度相关的特征有影响，这些影响不受遗传背景的干扰，因此是独立的。
