Population genetic diversity and conservation priority of prince’s pine Chimaphila umbellata populations around the south margin of their distribution

Abstract

How genetic diversity is maintained within a range of species is one of the crucial pieces of information in species conservation. Although the classical central-marginal hypothesis assumes genetic paucity in peripheral populations, this pattern is not always the case. The semi-shrub Chimaphila umbellata subsp. umbellate, population of which are located in the southernmost part of the subspecies distribution, is considered to be a threatened species in Japan. Thus, this study aimed to examine which populations should be preferentially conserved and if the central-marginal hypothesis can be applied to this case. Genetic diversity was examined in 15 populations of C. umbellata subsp. umbellata in Japan using 16 nuclear simple sequence repeat markers. Overall, the genetic diversity values within the populations did not correlate with the latitude of the population locality, although those of the southern marginal populations tended to be lower than those of populations in other regions. While the populations are genetically differentiated from each other, recent population size declines were only detected in a few cases. Bayesian inference of population structure revealed three genetically distinct groups. An approximate Bayesian computation revealed that these three genetic groups were derived from the ancient population in a recent times. The contribution of each population to total genetic diversity was estimated by removing a given population and recalculating the total genetic diversity. Only one population contributed to both gene diversity and allelic diversity, while several populations contributed to one or the other. Considering genetic diversity and structure, the conservation priority of Japanese populations of C. umbellata to preserve genetic diversity is discussed.