ISOZYME VARIATION WITHIN AND AMONG POPULATIONS OF HOSTA (LILIACEAE) IN KOREA

Forty-seven populations from seven species of Hosta in Korea and on Tsushima Island, Japan, were analyzed by starch gel electrophoresis to measure variation at six enzyme systems. High levels of isozyme diversity existed within and among populations of all species. It is suggested that Hosta venusta is a recent derivative of H. minor based on high Jaccard's Similarity Indices (SI) and possession of electrophoretic bands that represent an exact subset of those of H. minor with the exception of only one novel band (DIA 17) found in H. venusta. Hosta jonesii and H. tsushimensis may have developed from elements of H. minor separated by the last Ice Age. This hypothesis is supported by the evidence that: 1) the former two species had only one unique band, and a relatively high mean interspecific SI value with H. minor (range 0.402-0.479) and 2) similar morphological features. On the other hand, the uniformly low interspecific SI, high number of species-specific unique bands observed, and high morphological divergence suggest that H. minor, H. clausa, H. capitata, and H. yingeri have been isolated for a moderately long period of time. This indicates a probable geographic mode of speciation for these four species. In general, there is relatively good agreement of the phenetic relationships between the isozyme bands and the treatment by M. Chung based on morphometric analysis. Based on this information, four species groups could be recognized: 1) H. minor, H. venusta, H. jonesii, and H. tsushimensis; 2) H. yingeri; 3) H. capitata; and 4) H. clausa. This conclusion conflicts with previous taxonomic treatments of this genus. Finally, regression analysis revealed significant (P < 0.05) relationships between phenetic distance for presence/absence of each band and geographic distance for five species.