Lindroth Richard L, Wooley Stuart C, Donaldson Jack R, Rubert-Nason Kennedy F, Morrow Clay J, Mock Karen E
Department of Entomology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Department of Biological Sciences, California State University-Stanislaus, Turlock, CA, 95382, USA.
J Chem Ecol. 2023 Jun;49(5-6):235-250. doi: 10.1007/s10886-023-01409-2. Epub 2023 Feb 10.
Trembling aspen (Populus tremuloides) is arguably the most important deciduous tree species in the Intermountain West of North America. There, as elsewhere in its range, aspen exhibits remarkable genetic variation in observable traits such as morphology and phenology. In contrast to Great Lakes populations, however, relatively little is known about phytochemical variation in western aspen. This survey of phytochemistry in western aspen was undertaken to assess how chemical expression varies among genotypes, cytotypes (diploid vs. triploid), and populations, and in response to development and mammalian browsing. We measured levels of foliar nitrogen, salicinoid phenolic glycosides (SPGs) and condensed tannins (CTs), as those constituents influence organismal interactions and ecosystem processes. Results revealed striking genotypic variation and considerable population variation, but minimal cytotype variation, in phytochemistry of western aspen. Levels of SPGs and nitrogen declined, whereas levels of CTs increased, with tree age. Browsed ramets had much higher levels of SPGs, and lower levels of CTs, than unbrowsed ramets of the same genotype. We then evaluated how composite chemical profiles of western aspen differ from those of Great Lakes aspen (assessed in earlier research). Interestingly, mature western aspen trees maintain much higher levels of SPGs, and lower levels of CTs, than Great Lakes aspen. Phenotypic variation in chemical composition of aspen - a foundation species - in the Intermountain West likely has important consequences for organismal interactions and forest ecosystem dynamics. Moreover, those consequences likely play out over spatial and temporal scales somewhat differently than have been documented for Great Lakes aspen.
颤杨（Populus tremuloides）可以说是北美西部山间地区最重要的落叶树种。在那里，如同其分布范围内的其他地方一样，颤杨在形态和物候等可观察性状上表现出显著的遗传变异。然而，与五大湖地区的种群相比，人们对西部颤杨的植物化学变异了解相对较少。此次对西部颤杨植物化学的调查旨在评估化学表达在基因型、细胞类型（二倍体与三倍体）和种群之间如何变化，以及对发育和哺乳动物啃食的响应。我们测量了叶片氮、水杨素类酚糖苷（SPGs）和缩合单宁（CTs）的含量，因为这些成分会影响生物相互作用和生态系统过程。结果显示，西部颤杨的植物化学存在显著的基因型变异和相当大的种群变异，但细胞类型变异极小。随着树龄增长，SPGs和氮的含量下降，而CTs的含量增加。与相同基因型未被啃食的分株相比，被啃食的分株SPGs含量高得多，CTs含量低得多。然后，我们评估了西部颤杨的复合化学特征与五大湖颤杨（在早期研究中评估）的复合化学特征有何不同。有趣的是，成熟的西部颤杨树木的SPGs含量比五大湖颤杨高得多，CTs含量则低得多。在北美西部山间地区，作为基础物种的颤杨化学成分的表型变异可能对生物相互作用和森林生态系统动态具有重要影响。此外，这些影响在空间和时间尺度上的表现可能与五大湖颤杨有所不同。
