Morphological variation in the mangrove genus Avicennia in Australasia: systematic and ecological considerations

Morphological variation in flowers, fruits and leaves of A. alba, A. integra, A. lanata, A. marina and A. officinalis was assessed using multivariate techniques. Groupings based on 184 herbarium specimens gathered throughout the region showed no intermediates or potential hybrids between species. The most common and systematically troublesome species, A. marina, was considered further in a regional litterfall survey of 25 Australian sites, and in a detailed field study of eight locations within the Murray River estuary, Queensland. In both studies, morphological variation was correlated with environmental factors, including air temperature, rainfall, intertidal position and upriver location. Major differences were also observed within individuals, as shown in sun and shade leaves. These observations suggested that many attributes, especially of leaves, were affected by environmental factors, demonstrating their unsuitability in earlier systematic treatments. Other attributes reflecting putative subspecific genetic variation included bark character, extent of pubescence on calyx lobes, and stigma position in relation to anthers. These characterize three groupings of A. marina sites, related to major biogeographic zones within this region: southeastern Australia and New Zealand; northern and northeastern Australia and southern Papua New Guinea; and southwestern Australia.

Australian Systematic Botany

Australian Systematic Botany

3

1446-5701

N/A

2

19