Aspects of the ecology of the indigenous shrub Leptospermum scoparium (Myrtaceae) in New Zealand

Abstract

Geographic variation in leaf size and shape of the widespread and environmentally-tolerant indigenous shrub Leptospermum scoparium (Myrtaceae) was determined from 182 herbarium specimens collected over much ofits natural range. There were significant correlations with geographic and climatic factors — latitude, distance from coast, annual and winter temperatures. Seventeen seedling populations raised in a uniform environment showed that this leaf variation had a significant genetic component as did the variation in form and the age at first flowering. Flowering phenology in four year old plants from seven widely spread sites also differed significantly when grown together. Ecotypic differentiation is therefore clearly indicated in L. scoparium and this is discussed in relation to previous claims and explanations.

Sixteen communities dominated by L. scoparium in southern South Island differed in floristics. The density, basal area, age class distribution, and height of the Leptospermum stems also vary, and are correlated with environmental parameters. The eight climax or sub-climax stands of more extreme inland locations are compared with the eight seral stands from moister coastal habitats.

A plea is made for L. scoparium communities to be adequately represented in the New Zealand reserves system rather than ignored because of the often aggressive and seral characteristics of Its dominant species.

Key Words:

• Leptospermum scoparium
• manuka
• autecology
• ecotype
• Myrtaceae
• shrubland
• conservation
• New Zealand