What the heart wants: adaptive significance of cordate leaf morphology in Arnica (Asteraceae)

We studied how the leaf inclination of basal leaves of two species, heartleaf arnica (Arnica cordifolia Hook.) and broadleaf arnica (Arnica latifolia Bong.) varied with canopy cover in the Greater Yellowstone Ecosystem, Wyoming, USA in July and August, 2022. Basal leaves of heartleaf arnica possess cordate leaf bases while those of broadleaf arnica do not, leading to potential biomechanical limitations of the latter to persist in shaded forest understories. Leaf inclination was measured as the angle (degrees) between the petiole and leaf planes of basal leaves for each species; cordateness was measured as the ratio of leaf length on either side of the petiole insertion point in basal leaves of heartleaf arnica. Data collection are complete.

2022年7月至8月，我们于美国怀俄明州的大黄石生态系统（Greater Yellowstone Ecosystem）中，针对两种山金车属植物——心叶山金车（Arnica cordifolia Hook.）与宽叶山金车（Arnica latifolia Bong.），探究了其基生叶倾角随冠层覆盖度的变化规律。心叶山金车的基生叶具有心形叶基，而宽叶山金车则无该特征，这可能使后者在遮阴的林下生境中存活面临潜在的生物力学限制。本研究以叶柄与各物种基生叶叶平面的夹角（单位：度）作为叶倾角的量化指标；对于心叶山金车的基生叶，我们通过叶柄着生点两侧的叶片长度之比来表征其心形叶基特征。本数据集已完成全部数据采集工作。