Population dynamics of newly introduced species: Population fluctuations in adventive species in New Zealand
This contribution is an attempt to present instances of population fluctuations in adventive plants, treating the subject from two viewpoints.
A.-Fluctuations in species populations in relation to period of domicile of the particular species in New Zealand
Consideration of the adventive flora of New Zealand (circa 1400 species) shows that the constituent species, in terms of abundance and probable period of domicile, fall into one or other of the groups or categories detailed below.
GROUP I: Population usually small, derived in the main from repeated new intro- ductions, or escape from cultivation: species of early or recent introduction.
The populations of species in this group fluctuate from year to year, depending in large degree on opportumtIes for introduction, as related to import of certain commodities or growth of a particular crop, etc., e.g. Mexican poppy, Argemone mexicana L., *(T. W. Kirk, 1895, Taranaki, Hawke's Bay, Marlborough) in im- ported wheat; Gamelina sativa (L.) Grantz, (Cheeseman, 1883, Auckland) in imported linen flax seed; broomcorn millet, Pawicum miliaceum L., (Healy, 1944, North and South Island localities) in bird seed mixtures.