Species Area and Similar Relationships of Insects and Vascular Plants on the Southern Outlying Islands of New Zealand

Relationships of species numbers to island biogeographic variables (area, altitude, distance from source pool) have been studied for indigenous lepidoptera, diptera, coleoptera and vascular plants inhabiting seven of New Zealand's outlying islands to find the best statistical model for the linear relationship between species number and each of the biogeographic variables and for that between the insects and plants. Percentage of variance accounted for by the regressions was used as the criterion for best-fit.
For the species-area relationship and that between the insects and plants the best model was that using untransformed data; for the species-distance and species-altitude relationships only the log/log model for the plant species-altitude relationship yielded a statistically-significant value for the correlation coefficient.
Though there are significant correlations between island areas and the number of species per genus of both insects and vascular plants they support, this is not accepted as evidence for competitive exclusion. Simberloff's views (1970, 1978) on the subject are discussed and attention is drawn to the land arthropod fauna of the Bounty Islands in which there are 17 species each belonging to a different family.