Sand, salt, natives and neophytes

Environmental conditions are one of the main controls on the number of niches available in any community. Sand dunes are often unstable and infertile and some authors suggest this may lead to fewer niches, while others suggest it will lead to more. Two types of niche are measured, the realised or field niche - the n-dimensional hyperspace a species actually occupies, and the fundamental or experimental niche - the n-dimensional hyperspace the species could survive in. Realised niche (Beta-niche) breadths and overlaps are measured along a strong environmental gradient through some New Zealand dune systems. Some theories suggest that in such areas of instability and uncertainty niches are likely to be broad. Native and neophyte species are examined in this respect. Autecological responses to the environment are used as dimensions of a species fundamental niche. A number of species have been examined experimentally and their responses to different salinity and sand burial regimes are used as individual dimensions of the species niche.

Correlation between realised and fundamental niche parameters of some New Zealand species are made.