The Impact of Habitat Fragmentation on Wild 'Macadamia integrifolia' Maiden and Betche (Proteaceae) Population Viability

Abstract

'Macadamia integrifolia' Maiden and Betche (Family Proteaceae) is a medium-sized tree endemic to notophyll vine forests of South-Eastern Queensland, Australia (Hardner 2004), and the only major food crop to be domesticated from the Australian flora. Extensive clearing within its natural range has resulted in significant fragmentation of most of the habitat of 'M. integrifolia'. The majority of known populations are also located on private property and therefore outside of the conservation system. The species is listed as vulnerable under the EPBC Act 1999 (Cth), classifying it as likely to become extinct within the next 20 to 50 years. Conservation of this iconic species is important for the maintenance of Australian biodiversity, and the utilisation of wild germplasm may also provide a competitive edge to the Australian macadamia industry over international producers. This study aims to investigate the impact of habitat fragmentation on the viability of remnant 'M integrifolia' populations, with particular focus on (i) population demographic processes; (ii) mating system; and (iii) levels of genetic diversity and spatial genetic structure. Findings suggest that the species may be viable in the short-term, with stronger population growth rates in fragments than intact sites and equal levels of heterozygosity across all site area classes. Outcrossing rates were also high in the two medium sites in which mating system was analysed. Allelic richness was slightly lower in fragments compared to intact sites, potentially jeopardising the ability of fragmented populations to respond to selection pressures, however the biological significance of the small difference observed is unknown. The results of this study suggest that fragmented populations of 'M. integrifolia' may exist as metapopulations,and are of conservation value.