Neophyte

plants, which are spread by humans voluntarily or unintentionally outside their natural regions of origin

Often, they enter another continent as seeds along with shipped goods or are voluntarily introduced as ornamental or useful plant. Neophytes can establish themselves and spread under suitable environmental conditions at the new sites. In Europe, examples are the Japanese Knotweed Reynoutria japonica from East Asia and the Himalayan Balsam Impatiens glandulifera from the Himalaya. 

During the evolution, the species of the native flora adapted to coexist. Strongly concurring neophytes can crowd out the native flora, since no adaption has happen there. Thus, they are considered a potential thread for the biodiversity of the respective site.

The animal pendant - introduced alien animal species - are called invasive species (neozoa), the collective of all introduced organisms is called neobiota. Examples for invasive species in Europe are the corn borer and the vine pest, in Australia it is the wild rabbit.