Demographic structure, genetic diversity and habitat distribution of the endangered, Australian rainforest tree Macadamia jansenii help facilitate an introduction program

Macadamia jansenii is endemic to south-east Queensland, Australia, and is currently known from a single population 180 km north of the nearest wild population of its congener, the edible Macadamia integrifolia. A recently developed Macadamia recovery plan identified that this population was under significant threat and recommended a reintroduction program to safeguard against chance extinction of the single wild population. This study undertook demographic population census surveys, genetic analysis, habitat analysis and niche modelling to determine the potential long-term viability for the species, and to guide search and reintroduction programs. We expanded the known population size of the species to similar to 60 individuals (1 m and taller) spread over a 900-m distance along a single creek clumped into three subpopulations. There was moderate genetic diversity in the species and the subpopulations showed little genetic differentiation. We developed a potential habitat model combining abiotic variables and vegetation associations, and mapped areas of potentially suitable habitat for M. jansenii within its local area. These maps are being used to target searches for other populations and to guide the location of introduction populations.