Clonal Diversity, Genetic Structure, and Mode of Recruitment in a Prunus ssiori Population Established after Volcanic Eruptions

Seedling and root sprout recruitment after a volcanic deforestation was examined in a Prunus ssiori population. According to genotypes of five microsatellite (SSR) loci, 44 genets were identified among 188 ramets ≥ 5 cm DBH in a 2.3-ha plot in 2000. The genets formed mutually exclusive patches. Because only one repeat change in an SSR locus distinguished five genets from adjacent genets, there is a possibility that the five genets derived from somatic mutations as well as sexual reproduction. Thus, at least 39 genets originated from seedlings, and at least 144 ramets derived from root sprouts. The seedlings were recruited after the volcanic eruptions in 1739 and before 1972 because trees of 5 cm DBH were 28 years of age, estimated from annual rings. As the largest ramet recruited from a root sprout was estimated to be 94 years old, root sprout recruitment began between 1739 and 1906. Thus, the estimated minimum rates of recruitment from seedlings and root sprouts were 0.167$\text{y}^{-1}$and 0.618-2.182$\text{y}^{-1}$, respectively. The clonal diversity of the P. ssiori population (Simpson's D = 0.92) was higher than that of other clonal plant populations. The inbreeding coefficient was significantly negative (Wright's$F_{IS}$= - 0.069). These results suggest that the frequent seedling recruitment in an outbreeding system maintains the clonal diversity in the population.