A null model of guild proportionality, applied to stratification of a New Zealand temperate rain forest

Abstract

Much ecological theory assumes that the number of species that can coexist (by ‘species packing’) is limited, because competitive exclusion occurs when any pair of species within a guild is too similar — ‘species saturation’ or ‘niche limitation’. If such niche limitation occurs, the proportion of species in each guild should be relatively constant — ‘guild proportionality’. This concept is applied to the guilds represented by strata in a forest. A method is produced, and used to examine a New Zealand temperate rain forest. Most strata showed no deviation from a null model of no niche limitation, i.e. no tendency to guild proportionality. The proportion of lianes was more variable than in the null model, tending to be inversely related to the proportion of epiphytes, Canopy tree proportion was significantly more constant than in the null model, but this could be interpreted as a limit caused by the size of a canopy tree individual.