Cang F Alice, Welles Shana R, Wong Jenny, Ziaee Maia, Dlugosch Katrina M
Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona USA.
Utah Valley University Orem Utah USA.
Evol Appl. 2023 Dec 11;17(1):e13624. doi: 10.1111/eva.13624. eCollection 2024 Jan.
Plants demonstrate exceptional variation in genome size across species, and their genome sizes can also vary dramatically across individuals and populations within species. This aspect of genetic variation can have consequences for traits and fitness, but few studies attributed genome size differentiation to ecological and evolutionary processes. Biological invasions present particularly useful natural laboratories to infer selective agents that might drive genome size shifts across environments and population histories. Here, we test hypotheses for the evolutionary causes of genome size variation across 14 invading populations of yellow starthistle, , in California, United States. We use a survey of genome sizes and trait variation to ask: (1) Is variation in genome size associated with developmental trait variation? (2) Are genome sizes smaller toward the leading edge of the expansion, consistent with selection for "colonizer" traits? Or alternatively, does genome size increase toward the leading edge of the expansion, consistent with predicted consequences of founder effects and drift? (3) Finally, are genome sizes smaller at higher elevations, consistent with selection for shorter development times? We found that 2C DNA content varied 1.21-fold among all samples, and was associated with flowering time variation, such that plants with larger genomes reproduced later, with lower lifetime capitula production. Genome sizes increased toward the leading edge of the invasion, but tended to decrease at higher elevations, consistent with genetic drift during range expansion but potentially strong selection for smaller genomes and faster development time at higher elevations. These results demonstrate how genome size variation can contribute to traits directly tied to reproductive success, and how selection and drift can shape that variation. We highlight the influence of genome size on dynamics underlying a rapid range expansion in a highly problematic invasive plant.
植物在物种间的基因组大小表现出异常的差异，而且它们的基因组大小在物种内的个体和种群间也会有显著变化。这种遗传变异的方面可能会对性状和适合度产生影响，但很少有研究将基因组大小的分化归因于生态和进化过程。生物入侵提供了特别有用的天然实验室，以推断可能驱动基因组大小在不同环境和种群历史中发生变化的选择因素。在这里，我们对美国加利福尼亚州14个入侵的黄矢车菊种群的基因组大小变化的进化原因进行了假设检验。我们通过对基因组大小和性状变异的调查来探讨：（1）基因组大小的变异是否与发育性状变异相关？（2）在扩张前沿，基因组大小是否更小，这与对“殖民者”性状的选择一致？或者，基因组大小是否朝着扩张前沿增加，这与奠基者效应和遗传漂变的预测结果一致？（3）最后，在较高海拔处基因组大小是否更小，这与对较短发育时间的选择一致？我们发现，所有样本中的2C DNA含量变化了1.21倍，并且与开花时间变异相关，即基因组较大的植物繁殖较晚，一生的头状花序产量较低。基因组大小朝着入侵前沿增加，但在较高海拔处趋于减小，这与分布范围扩张期间的遗传漂变一致，但可能在较高海拔处对较小基因组和更快发育时间有强烈选择。这些结果表明基因组大小变异如何能够促成与繁殖成功直接相关的性状，以及选择和漂变如何能够塑造这种变异。我们强调了基因组大小对一种极具问题的入侵植物快速分布范围扩张背后动态的影响。
