Evaluation of genetic variation in phenotypic plasticity in response to temperature in wild <i>Primula sieboldii</i>

Abstract Genetic diversity among and within wild populations is important in fluctuating environments. Phenotypic plasticity is also essential under environmental changes, especially those that are shorter than the species lifespan. Primula sieboldii is in danger of extinction in the wild in Japan; understanding how wild populations can respond to environmental fluctuations is important for its long‐term conservation. To examine genetic variation in phenotypic plasticity in response to temperature, we grew 38 genets in 2004 and 43 genets in 2005 derived from five wild P. sieboldii populations at three experimental sites at different altitudes. The response to temperature on the traits related to bud initiation differed most among populations. Mean budding rate was 61% at experimental site 3 (Yatsugatake) and at least 90% at experimental site 1 (Tsukuba) and 2 (Suwa). In particular, that of the Saitama population at experimental site 3 (Yatsugatake) (30.8%) was considerably lower than those of other populations, indicating that experimental site 3 (Yatsugatake) was a severe environmental condition for the Saitama population, with the mean February temperature about 9°C lower than at Saitama. Days to bud initiation of the Saitama population were significantly shorter than those of the other populations at other environmental sites, but were longer than at experimental site 3 (Yatsugatake). Phenotypic plasticity of days to bud initiation differed significantly among populations in both years. Most genets of the Saitama population died at experimental site 3 (Yatsugatake), but some had high phenotypic plasticity that allowed the population to survive in this low‐temperature environment.