Biogeography and origin of Lilium longiflorum and L. formosanum (Liliaceae) endemic to the Ryukyu Archipelago and Taiwan as determined by allozyme diversity.

Allozyme diversity on 13 isozyme loci was investigated for two bulbous species, Lilium longiflorum and L. formosanum, endemic to the subtropical archipelago of continental origin located in East Asia. Degrees of allozyme variability and divergence for L. longiflorum were very high for insular endemic species, indicating relatively longtime persistence of the present widespread distribution across many islands in this phenotypically little-changed species. Lilium formosanum exhibited rather lower variability and divergence than did L. longiflorum and was genetically close to the southern peripheral populations of L. longiflorum with 0.978 as its highest genetic identity value. Combined with other biological and insular geohistorical information, our results suggest that L. longiflorum was established around the end of the Pliocene when the current distribution area was still a continuous part of the ancient Asian continent, and L. formosanum was derived from southern populations of L. longiflorum around the late Pleistocene when the mainland of Taiwan was completely separated from the adjacent islands and the main continent. Depauperization of allozyme variability in some L. longiflorum populations was found on islands with lower altitudes. This reflects bottleneck effects after the complete or almost complete submergence of such low islands during the archipelago's development.