Most of the plants morphologically identified as the introduced dandelions are known to be the hybrids between the native diploid and the introduced triploid dandelions. From the viewpoint of environmental indicator species, we clarified the environmental characteristics of the habitats of native and hybrid dandelions (tetraploid hybrids and triploid hybrids), analyzing the relationships between the distribution pattern of these dandelions and the habitat factors such as vegetation types, soil pH (H2O), soil hardness and illumination intensity in the campus of the National Institute of Livestock and Grassland Science. It was found that the native dandelions mainly occurred at slightly disturbed habitats with weakly acidic soil covered by forest edge species. In contrast, the hybrid dandelions, typically tetraploid hybrids, tended to occur at intensively disturbed habitats with relatively hard soil of neutral pH (H2O). We also performed clone analysis to reveal the genetic structures of dandelion populations, and analyzed the distribution patterns of each of the genetically identical clones. Based on the results obtained, we evaluated the validity of environmental indicator for ruderal and urban environments by the pair of native dandelions and tetraploid hybrids.
