High Levels of Diversity in the Phytochemistry, Ploidy and Genetics of theMedicinal Plant Acorus calamus L.
Acorus calamus L. is an emergent aquatic macrophyte that is used in several medicines and food supplements. A. calamus ecotypes with low concentrations of β-asarone can be used for medicinal purposes. We investigated 50 populations of this species, representing the entire natural distribution range in Indian Himalayan Region (IHR), to understand natural variations in β-asarone concentration, ploidy level and genetic divergence. Our results showed that: 1) all four cytotypes (diploid, triploid, tetraploid and hexaploid) of A. calamus exist in natural populations in the IHR; 2) the β-asarone concentration is highly correlated with the ploidy level (diploid and hexaploid populations exhibit low β-asarone concentrations, whereas triploids and tetraploids show high β-asarone concentrations); 3) there is a significant correlation between the β-asarone concentration and its distribution along latitudinal and longitudinal ranges, but not ecological factors (mean annual temperature and mean annual precipitation); and 4) geographic boundaries play an important role in the population divergence of A. calamus. This study provides a foundation for understanding the genetic basis of natural variation in complex traits of A. calamus and for devising conservation strategies for this medically important plant.