Relations Between Native and Exotic Plant Guilds in the Upper Clutha, New Zealand

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Abstract
(1) The native and exotic plant guilds of the Upper Clutha catchment, New Zealand, are examined. The two guilds produced classifications of the quadrats that were no more different than those using random groups of species, suggesting that the two guilds follow the same vegetational boundaries. There was some evidence, however, that the guilds differ in the environmental factors with which they are correlated. (2) The ratio of the two guilds differed between quadrats, and inverse classification showed significant differences in their distribution. It is concluded that the two guilds differ ecologically, although this distinction is far from complete. (3) The available evidence indicates that the importance of exotics has steadily increased over the past fifty years, and is probably still increasing. (4) There was more structure, as seen in the quadrat-species two-way table, in the native guild than in the exotic guild, even allowing for guild size. The native guild was slightly more related to the environment. However, the total community was more related so the exotic guild than to the native guild, an effect that did not seem to be due to guild size. (5) It is concluded that, in spite of the differences shown, the native and exotic guilds now form one community at each point. The exotic guild tends to determine the structure of the community, but it is still invading and therefore not yet at equilibrium.