Geographical variation of Artemisia leaf morphology along a large environmental gradient in China

Although it is widely acknowledged that the variation in leaf morphology reflects the adaptation of plants to local environments, we know little about how leaf morphology varies at large scales and which environmental factors drive such variation, especially for closely related species. Along broad climatic and soil gradients in eastern and central China, we evaluated the geographical pattern and the effects of environmental gradients on the variation in leaf geometric morphometrics of 1,041 plants of 60 Artemisia species. Species identity explained the largest variation in leaf geometric morphometrics. Leaf geometric morphometrics exhibited a significant latitudinal pattern. As latitude increased, oblanceolate moderate three-lobed leaves changed gradually to elliptic integrifolious ones. Regional environmental gradients, including mean annual precipitation (MAP), soil organic carbon (SOC) and pH, had significant (but different) effects on leaf geometric morphometrics. These results suggest that although leaf geometric morphometrics of Artemisia are under strong genetic control, they respond significantly to changing environmental conditions. Our study demonstrates that the high responsiveness in leaf morphology to the environment could reflect important adaptation by which plants function efficiently along broad environmental gradients.