Data from: Variation in seasonal timing traits and life history along a latitudinal transect in Mimulus ringens

Seasonal timing traits are commonly under recurrent, spatially-variable selection, and are therefore predicted to exhibit clinal variation. Temperate perennial plants often require vernalization to prompt growth and reproduction; however, little is known about whether vernalization requirements change across the range of a broadly distributed species. We performed a critical vernalization duration study in Mimulus ringens, coupled with population genomic analysis. Plants from 8 populations spanning the latitudinal range were exposed to varying durations of 4°C vernalization between 0-56 days, and flowering response was assessed. RADSeq was also performed to generate 1,179 polymorphic SNPs, which were used to examine population structure. We found unexpected life history variation, with some populations lacking vernalization requirement. Population genomic analyses show that these life history variants are highly divergent from perennials, potentially revealing a cryptic species. For perennial populations, minimum vernalization time was surprisingly consistent. However, once vernalized, northern populations flowered almost 3 weeks faster than southern. Further, southern populations exhibited sensitivity to vernalization times beyond flowering competency, suggesting an ability to respond adaptively to different lengths of winter. M. ringens therefore reveals evidence of clinal variation, and provides opportunities for future studies addressing mechanistic and ecological hypotheses both within and between incipient species.

物候时序性状通常处于反复发生且空间异质性的选择压力之下，因此理论上应表现出渐变群变异（clinal variation）。温带多年生植物通常需要春化作用（vernalization）来启动生长与生殖过程，但目前对于广布物种的分布范围内春化需求是否会发生变化仍知之甚少。本研究以菱叶沟酸浆（Mimulus ringens）为对象，开展了关键春化时长实验，并结合种群基因组学分析。我们选取覆盖其纬度分布范围的8个种群的植株，将其置于4℃环境下，接受0至56天不等时长的春化处理，并评估其开花响应。本研究同时开展了限制性位点相关DNA测序（RADSeq），共获得1179个多态性单核苷酸多态性（Single Nucleotide Polymorphism，SNP）位点，以此分析种群遗传结构。研究发现了意料之外的生活史变异：部分种群完全不存在春化需求。种群基因组学分析显示，这些生活史变异类群与典型多年生类群存在显著遗传分化，或暗示存在一个隐存物种。对于多年生种群而言，其最低春化时长意外地保持一致。但完成春化后，北方种群的开花速度比南方种群快近三周。此外，南方种群对超出开花所需阈值的春化时长表现出敏感性，表明其能够对不同时长的冬季产生适应性响应。因此，菱叶沟酸浆（Mimulus ringens）为渐变群变异现象提供了实证支持，同时为后续针对新形成物种内外的机制与生态假说开展研究提供了契机。