Evolution of Plants of Ullung Island II

This proposal seeks support for continued studies on the evolution of the endemic vascular flora of Ullung Island, Korea. This island is 70 km2 and located 150 km E of the Korean peninsula in the Eastern Sea (Sea of Japan) at 37 N latitude. Confined to Ullung Island are 28 endemic angiosperms. This island is of volcanic origin and has had no apparent land connections to continental areas. Radiometric dates place the island at 1.8 million years old. Previous botanical work on Ullung Island has provided a good inventory of taxa, a survey of vegetation, an analysis of human impact, and general discussions on phytogeography. What has not been investigated is evolution of the endemic flora with reference to specific origins and ancestors, character change during speciation in the island, and the founder effects and genetic drift on variation within endemic taxa. Studies completed or in advanced stages of completion in the first phase of the Ullung Island project are: (1) origin of the two endemic species of Acer (Aceraceae); (2)origin and phytogeography of the endemic Hepatica maxima (Ranunculaceae);(3) analysis of genetic variation within and among populations of the endemic species of Acer and Hepatica in comparison to mainland progenitors; (4) general karyological survey of endemic species; and (5) specific karyological investigations of the endemic Hepatica maxima in comparison with its relatives. This proposed project has three parts. First, we will determine relationships between the endemic species Abelia insularis (Caprifoliaceae), Dystaenia takesimana. (Umbelliferae), Fagus multinervis (Fagaceae), Rubus takesimensis (Rosaceae), Tilia insularis (Tiliaceae), and Viola insularis (Violaceae) with their presumptive progenitors, respectively, Abelia coreana (Korea), Dystaenia ibukiensis (Japan), Fagus crenata (Japan), Rubus crataegifolius (Korea and Japan), Tilia japonica (Tiliaceae) and Viola kusanoana (Korea and Japan). Second, we will analyze genetic variation using AFLP techniques within and among these endemic island taxa and their continental progenitors to determine genetic consequences of founder effects as progenitor migrants have arrived to the island and established populations. Third, we will also assess more directly the effects of establishment of founder populations by comparing genetic variation within and among populations of the following taxa that occur natively in Ullung Island and also are found in neighboring Korea and/or Japan: Adenocaulon himalaicurn (Asteraceae); Styrax obassia (Styracaceae); Viola albida var. cherophylloides, V. grypoceras, and V. veracunda (Violaceae). The overall objective is to summarize the patterns and offer suggestions on processes of evolution during phyletic evolution in Ullung Island.

Research on the flowering plants of Ullung Island, Korea, has provided new insights on plant evolution in oceanic archipelagos. The classic pattern of evolution in islands is for an immigrant to arrive from some continental region, bringing with it only a small position of the genetic resources found in the parental population. Divergence through time, with adaptation into diverse ecological habitats, results in a genetically closely related complex of species that have different morphological features and ecological tolerances. Studies in the oceanic Ullung Island reveal a different pattern of evolution. Our investigations have shown that ancestral immigrants to the island have diverged sufficiently in genetic and morphological attributes to be regarded as new island species, but that little additional divergence has occurred. Further, genetic variation among populations of island species shows no geographic correlation, with individuals in the island behaving as one large population. This is called anagenetic (as opposed to splitting or cladogenetic) speciation. The young age of the island (1.8 million years) and its relatively uniform vegetation and ecology may explain the lack of intra-island genetic divergence and speciation. Ullung Island represents an extreme case whereby all plant speciation has occurred anagenetically. Other archipelagos also show different levels of anagenesis, but with splitting events (cladogenesis) and adaptive radiation also having taken place. Overall, anagenetic speciation in islands appears to be much more significant than believed previously and suggests another general model for explaining species diversity in oceanic archipelagos.