Donohue Kathleen, Dorn Lisa, Griffith Converse, Kim EunSuk, Aguilera Anna, Polisetty Chandra R, Schmitt Johanna
Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Evolution. 2005 Apr;59(4):740-57.
Seasonal germination timing strongly influences lifetime fitness and can affect the ability of plant populations to colonize and persist in new environments. To quantify the influence of seasonal environmental factors on germination and to test whether pleiotropy or close linkage are significant constraints on the evolution of germination in different seasonal conditions, we dispersed novel recombinant genotypes of Arabidopsis thaliana into two geographic locations. To decouple the photoperiod during seed maturation from the postdispersal season that maternal photoperiod predicts, replicates of recombinant inbred lines were grown under short days and long days under controlled conditions, and their seeds were dispersed during June in Kentucky (KY) and during June and November in Rhode Island (RI). We found that postdispersal seasonal conditions influenced germination more strongly than did the photoperiod during seed maturation. Genetic variation was detected for germination responses to all environmental factors. Transgressive segregation created novel germination phenotypes, revealing a potential contribution of hybridization of ecotypes to the evolution of germination. A genetic trade-off in germination percentage across sites indicated that determinants of fitness at or before the germination stage may constrain the geographic range that a given genotype can inhabit. However, germination timing exhibited only weak pleiotropy across treatments, suggesting that different sets of genes contribute to variation in germination behavior in different seasonal conditions and geographic locations. Thus, the genetic potential exists for rapid evolution of appropriate germination responses in novel environments, facilitating colonization across a broad geographic range.
季节性萌发时间强烈影响植物的终生适合度，并可能影响植物种群在新环境中定殖和持续存在的能力。为了量化季节性环境因素对萌发的影响，并测试基因多效性或紧密连锁是否是不同季节条件下萌发进化的重要限制因素，我们将拟南芥的新型重组基因型分散到两个地理位置。为了将种子成熟期间的光周期与母本光周期所预测的种子散播后季节解耦，重组自交系的重复样本在可控条件下的短日照和长日照条件下生长，其种子于6月在肯塔基州（KY）以及6月和11月在罗德岛州（RI）进行散播。我们发现，种子散播后的季节条件对萌发的影响比种子成熟期间的光周期更强。检测到了对所有环境因素的萌发反应的遗传变异。超亲分离产生了新的萌发表型，揭示了生态型杂交对萌发进化的潜在贡献。不同地点间萌发率的遗传权衡表明，萌发阶段或之前的适合度决定因素可能会限制给定基因型能够栖息的地理范围。然而，萌发时间在不同处理间仅表现出较弱的基因多效性，这表明在不同的季节条件和地理位置下，不同的基因集对萌发行为的变异有贡献。因此，在新环境中，存在快速进化出适当萌发反应的遗传潜力，这有利于在广泛的地理范围内定殖。
