Department of Biology, Duke University, Durham, NC.
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC.
J Hered. 2019 Jul 1;110(4):467-478. doi: 10.1093/jhered/esz019.
The timing of seed germination determines the environment experienced by a plant's most vulnerable life stage-the seedling. Germination is environmentally cued, and genotypes can differ in their sensitivity to environmental cues. When genotypes differ in their response to cues, and when cues accurately predict the postgermination environment, the postgermination environment experienced by seedlings can itself have a genetic basis and potential to evolve. We tested for genetic differences in the postgermination environment using Arabidopsis thaliana genotypes that vary in seed dormancy, a trait known to alter germination time. We dispersed seeds into the field in 5 seasonal cohorts over 1.5 years, observed germination timing for 5297 individuals, and measured the soil temperature and moisture experienced by individuals throughout their life cycle. We found that genotypes differed in the environments they experienced during seedling establishment. This environmental variation occurred because genotypes differed in their environmental sensitivity to germination cues, and pregermination cues were correlated with postgermination environments. Seeds exhibited temporal habitat selection by germinating into a nonrandom subset of environmental conditions available, and seed dormancy increased the consistency of habitat selection. Strikingly, the postgermination environment affected fitness by altering the probability of seedling survival such that genotypes that engaged in stronger habitat selection were less likely to reach reproduction. Our results suggest that environmentally cued development may be a widespread mechanism by which genotypes can differ in the environment they experience, introducing the possibility that the environment itself can be inherited and can evolve.
种子萌发的时间决定了植物最脆弱生命阶段——幼苗所处的环境。萌发是受环境 cues 影响的，不同基因型对环境 cues 的敏感性也不同。当基因型对 cues 的反应不同，并且 cues 能准确预测萌发后的环境时，幼苗所经历的萌发后环境本身就具有遗传基础和进化潜力。我们使用拟南芥不同休眠特性的基因型来检验萌发后环境中的遗传差异，休眠特性是已知能改变萌发时间的性状。我们在 1.5 年内的 5 个季节性批次中将种子散布到野外，观察了 5297 个个体的萌发时间，并测量了个体整个生命周期中所经历的土壤温度和湿度。我们发现，在幼苗建立过程中，基因型之间的环境存在差异。这种环境变化是因为基因型在对萌发 cues 的环境敏感性上存在差异，并且萌发前 cues 与萌发后环境相关。种子通过萌发到可用环境条件的非随机子集来表现出时间上的栖息地选择，而种子休眠增加了栖息地选择的一致性。引人注目的是，萌发后环境通过改变幼苗存活的概率来影响适应性，从而使得进行更强栖息地选择的基因型更不可能达到繁殖。我们的研究结果表明，受环境 cues 影响的发育可能是一种广泛存在的机制，通过这种机制，基因型可以在它们所处的环境中存在差异，从而引入了环境本身可以遗传并进化的可能性。
