Biogeographic origins and reproductive mode of naturalised populations of Acacia saligna

Abstract

Acacia saligna (Labill.) H.L.Wendl. is a species complex with an extensive history of anthropogenic utilisation and distribution. The taxon is naturalised and invasive in many countries. Extensive morphological variation makes accurate taxonomic identification of populations difficult. We used population genetic analysis to determine the biogeographic origins of 12 naturalised populations sampled from throughout south-eastern South Australia and assess the mode of reproduction (seedling or root suckering) at sites with active recruitment. Ten naturalised populations were assigned to Eastern ‘saligna’, although some also showed a lesser degree of affinity with other entities. A single population was assigned to Western ‘saligna’, but showed some affinity with Eastern ‘saligna’, and one population assigned to subsp. ‘lindleyi’ showed some affinity with Northern ‘lindleyi’. These assignments suggest that although several genetic entities of A. saligna are represented in South Australia, the majority of germplasm has originated from native populations of Eastern ‘saligna’ located around Esperance on Western Australia’s southern coast. Genetic diversity is limited in naturalised A. saligna compared with that present in the native range, suggesting a restricted number of historical introductions. Reproduction is predominantly by seedling recruitment, as opposed to clonal reproduction.