Inferring establishment histories in populations of Quercus dentata (Fagaceae) from the analysis of spatial genetic structure

Abstract.

Considerations of colonization history of an oak species across multiple populations would provide insight into whether different population histories generate near random or significant fine-scale spatial genetic structure. This study used multilocus allozyme genotypes mapped from three populations of Quercus dentata in South Korea: one population, in Mt. Sobaek (SOB), is considered to be recently established from “off-site” seed sources; the second population, located in Dongraedo (DON), Jollanamdo Province may have been established from “on-site” old individuals; and the last population, in Haegumgang (HAE), Gyeongsangnamdo Province, is probably in an intermediate stage between SOB and DON. Coancestry measures (f_ij), Ripley’s L-statistics, and Wright’s F statistics were calculated to examine the distribution of individuals and spatial genetic structure both within and between populations. Ripley’s L-statistics indicated significant aggregation of individuals, and patterns varied depending on populations. A significant positive fine-scale genetic structure at 10 m distance was detected in population DON, whereas SOB and HAE populations mostly showed very weak patterns and indeed genotypes were essentially randomly distributed. These results appear to be consistent with the proposed histories of population establishment. The levels of genetic diversity within populations of Q. dentata examined in this study (H_e=0.103) were lower than in most of the oaks, which may reflect rarity and discontinuity in the distribution of Q. dentata. A small but significant deficit of heterozygosity was detected within populations (pooled F_IS=0.040), which is also consistent with most of the examined oaks. Low but significant differentiation between the three populations of Q. dentata (mean F_ST=0.030) agrees with that found for other oaks in South Korea, reflecting long-distance pollen movement by wind.