Document ID: chunk:federal_register_of_legislation:F2023L01376:reg:2:p2
Version: federal_register_of_legislation:F2023L01376
Segment Type: reg
Provision Reference: reg 2 (pt 2/8)
Character Range: 21526–24512

Cream          Thick, hard, smooth shell; edible kernel
Macadamia jansenii      3 leaves per node; smooth edges to leaves; green or pink new flush  Cream          Small with thin, smooth shell; bitter kernel
Macadamia ternifolia    3 leaves per node; spiny leaves; pink new flush                     Pink           Small with thin, smooth shell; bitter kernel
Macadamia tetraphylla   4 leaves per node; spiny leaves, pink new flush                     Pink           Thick, hard, rough shell; edible kernel

Most knowledge of Macadamia has been gained through research to support the commercial industry, which has focused on M. integrifolia, and M. tetraphylla; further research is required to determine whether this knowledge can validly be applied to the other two species. In recent times, the industry has expanded its research to investigate the potential value of wild trees of these species and to explore characteristics of M. ternifolia and M. jansenii that may be of value to the industry.
Macadamia integrifolia is highly susceptible to fire damage (O'Hare et al. 2004). A known response by orchard trees in response to fires hot enough to destroy the cambium layer, is to shoot from roots below or near the ground (Rosedale 1969); this results in multi-stemmed trees. Multi-stemmed plants are common in wild populations of all four species, so it is assumed that all species are similarly susceptible to fire.
Pollen flow between Macadamia trees growing in highly fragmented landscapes has been reported at distances of up to 3 km (Neal 2007); it is likely that in more intact forest habitats, pollen exchange occurs across much shorter distances. Flower production is also reduced in shaded environments, such as under the rainforest canopy. Whilst self-pollination can occur in Macadamia, cross-pollination results in greater nut production.
Trees that display morphological characteristics of both M. integrifolia and M. tetraphylla are found in a hybrid zone up to 20 km wide (Peace 2005). While similar observations have not been reported for M. integrifolia and M. ternifolia, DNA marker studies have confirmed hybrid genotypes (Peace 2005). Hybridisation may be an important survival mechanism, providing a means of adaptation to changed environmental conditions, and evidence of the evolutionary retention of genes better adapted to the same. Hybrid populations offer important foci for ecological research, potentially improve long-term species viability where overlap occurs, and may be important conservation priorities.
Seed dispersal is by small rodents, cockatoos and gravity fall, probably with some assistance from local stream flooding. The role of seed predators such as cockatoos and rodents in effecting seed dispersal is likely to be limited. Studies of the caches of the introduced black rat (Rattus rattus) – a common predator of trees in orchards, backyards and wild populations close to urban areas – found they did not contain any undamaged nuts;