Primula sieboldii E. Morren is a perennial clonal herb that is widely distributed in Japan, but indanger of extinction in the wild. In a previous study, we revealed the genetic diversity of the speciesusing chloroplast and nuclear DNA and used this information to define conservation units.However, we lacked information on adaptive genetic diversity, which is important for long-termsurvival and, thus, for the definition of conservation units. In order to identify adaptive traits thatshowed adaptive differentiation among populations, we studied the genetic variation in sixquantitative traits within and among populations for 3 years in a common garden using 110 genetsfrom five natural populations from three regions of Japan. The number of days to bud initiation wasadaptive quantitative trait for which the degree of genetic differentiation among populations (QST)was considerably larger than that in eight microsatellite markers (FST). The relationship betweenthis trait and environmental factors revealed that the number of days to bud initiation wasnegatively correlated, with the mean temperature during the growing period at each habitat. Thissuggests that adaptive differentiation in the delay before bud initiation was caused by selectivepressure resulting from temperature differences among habitats. Our results suggest that based onadaptive diversity and neutral genetic diversity, the Saitama population represents a newconservation unit
