Seed mass in relation to abundance patterns in New Zealand tussock grasslands : A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science (Honours) at Lincoln University

Abstract

Seed mass is thought to be a critical plant trait, which determines patterns of species abundance. This is based on a presumed trade-off between seed size and seed number, and a hypothesised relationship between recruitment and seed size. The relationship between seed mass and abundance was examined in a long-term study of 71 tussock grassland species of south-eastern New Zealand. This study was unique in that the colonisation and extinction rates were also known for the species. A significant relationship was found between colonisation ability and seed mass. Species with intermediate sized seeds were better colonists. This result indicates that colonising ability is related to both dispersal and recruitment. Colonisation success is expected to be important factor determining abundance patterns in communities. However, small-seeded Hieracium species were found to be the most abundant species. These results indicate that, in south-eastern New Zealand tussock grassland communities seed mass is an not a important factor influencing community abundance and structure. More likely a complex interaction of a number of key plant traits influence species abundance.