Range-wide provenance variation in growth and morphological characteristics of Casuarina equisetifolia grown in Northern Australia

Variation in 14 growth and morphological characteristics was assessed in a 30-month-old range-wide provenance trial of Casuarina equisetifolia in Weipa, north Queensland, Australia. The trial compared 59 provenances from throughout the species' occurrence in four broad regions, i.e. natural occurrences in Australia/the Pacific, natural occurrences in South-East Asia, introduced populations in Asia and introduced populations in Africa. The following characteristics were assessed: axis persistence; stem straightness; density, thickness, angle and length of permanent branches; length and thickness of deciduous branchlets; stem and foliage damage; flowering and fruiting; and height and diameter growth. There were significant differences between provenances in most of the characteristics assessed. Principal component analyses suggested a pattern of geographic variation among provenances from the natural distribution, with provenances in Australia and the Pacific Islands forming a separate group from those in South-East Asia. No one provenance showed superior performance for all the characteristics, suggesting that inter-provenance hybridisation may be useful in genetic improvement programs. Most provenances from Malaysia and Thailand grew vigorously but lacked stem straightness while some Kenyan seedlots, though inferior in growth, were superior in stem form. The wide geographic range and extensive cultivation of the species offer great potential for selection of genetic material for tree improvement programs. Crown Copyright (C) 2000 Elsevier Science B.V.