Evolution of Dystaenia takesimana (Apiaceae), endemic to Ullung Island, Korea

Dystaenia (Apiaceae) consists of two species, one distributed in Japan (D. ibukiensis), and the other endemic to Ullung Island, Korea (D. takesimana). In comparison with representative outgroup taxa in Ligusticum, Seseli, Angelica, and Osmorhiza, Dystaenia is shown to be monophyletic based on sequences from chloroplast trnL-F intron and spacer regions confirming previously published results using ITS sequences. Loss of one large part of trn L-F in D. takesimana strongly suggests that this species evolved from D. ibukiensis rather than the reverse. AFLP analysis within and among twelve populations (six from each species; total 126 individuals) using three primer combinations reveals 130 reliable fragments. Neighbour-joining analysis shows the two species to be distinct populational systems. Levels of overall genetic variation as measured by Shannon Diversity are significantly higher in D. takesimana. Geographic structuring of genetic variation occurs within D. ibukiensis but not within D. takesimana, suggesting that the Ullung species exists as a single population. It is hypothesised that after a founder-effect reduction of genetic variation, anagenetic speciation may have occurred in D. takesimana by gradual morphological divergence accompanied by accumulation of genetic variation through mutation, recombination and drift.