Spatiotemporal monitoring of the rare Northern dragonhead, Dracocephalum ruyschiana (Lamiaceae): SNP genotyping and environmental niche modelling herbarium specimens

Aim: We have studied spatiotemporal genetic change in the Northern
dragonhead, a plant species that has experienced a drastic population
decline and habitat loss in Europe. We add a temporal perspective to the
monitoring of dragonhead in Norway by genotyping herbarium specimens up to
200 years old. We also assess whether dragonhead has achieved its
potential distribution in Norway. Location: Europe (mainly Norway)
Methods: We have applied a microfluidic array consisting of 96 SNP markers
on 130 herbarium specimens collected from 1820 to 2008, mainly from Norway
(83) but also beyond (47). We have compared our new genotype data with
existing data from modern samples. We have modelled the species’
environmental niche and potential distribution in Norway using sample
metadata and observational records. Results: The SNP array successfully
genotyped all included herbarium specimens. The captured genetic diversity
was negatively correlated with distance from Norway. The historical-modern
comparison revealed similar genetic structure and diversity across space
and limited genetic change through time in Norway. The ENM suggests that
dragonhead is anchored in warmer and drier habitats. Main conclusions:
With appropriate design procedures, the SNP array technology is promising
for genotyping old herbarium specimens. We found no signs of any regional
bottleneck. The regional areas in Norway have remained genetically
divergent, however, both from each other and more so from populations
outside of Norway, rendering continued protection of the species in Norway
relevant. The ENM suggests that dragonhead has not fully achieved its
potential distribution in Norway.

研究目的：本研究针对欧洲种群急剧缩减、栖息地丧失的植物物种——北青兰（Northern dragonhead）的时空遗传变化展开探究。本研究通过对距今最长可达200年的标本馆标本进行基因分型，为挪威境内北青兰的监测增添了时间维度视角；同时，我们还评估了挪威境内的北青兰是否已达到其潜在分布范围。
研究区域：欧洲（以挪威为主）。
研究方法：我们采用搭载96个单核苷酸多态性（Single Nucleotide Polymorphism, SNP）标记的微流控阵列（microfluidic array），对1820年至2008年间采集的130份标本馆标本进行基因分型，其中83份采自挪威境内，剩余47份采自挪威以外区域。我们将新生成的基因型数据与已公开的现代样本数据开展比对分析。此外，我们借助样本元数据与野外观测记录，构建了该物种在挪威境内的生态位与潜在分布模型。
研究结果：该SNP阵列成功完成了所有纳入标本的基因分型工作。检测得到的遗传多样性与距挪威的空间距离呈负相关。历史样本与现代样本的比对结果显示，挪威境内北青兰的空间遗传结构与遗传多样性均无明显差异，且随时间推移的遗传变化极为有限。生态位模型（Environmental Niche Model, ENM）结果表明，北青兰偏好栖息于温暖干燥的生境中。
主要结论：只要采用合理的实验设计方案，SNP阵列技术在老旧标本馆标本的基因分型领域具备良好的应用前景。本研究未发现任何区域种群瓶颈的相关迹象。不过，挪威境内的区域种群彼此之间以及与挪威境外种群均存在明显的遗传分化，因此持续保护挪威境内的该物种仍具有重要意义。生态位模型结果显示，挪威境内的北青兰尚未完全达到其潜在分布范围。