Behavior of a newly introduced dandelion Taraxacum section Ruderalia population and discovery of introduced diploid plants

Abstract

A population of an artificially introduced dandelion species was investigated to follow the early settlement behavior of an introduced species in Japan. At a developed field in the Tokyo Bay Area, many seeds of Taraxacum officinale Weber were sown on artificial soil in 1998, creating a population with density as high as 1×10^2 plants/m^2. In 2006, the population was lower in density. Most of the seedlings appeared in early summer and had died by autumn. A few of the seedlings appeared in autumn and had a relatively high survival rate. The population had a high percentage of pure individuals of the introduced dandelion in 2006, although other populations growing in some major cities in central Japan have high percentages of hybrids between the introduced and a native dandelion species. This is the first documentation of diploid individuals of introduced dandelions growing in Japan; these diploids represented about 15% of the individuals of the population.