Document ID: chunk:federal_register_of_legislation:F2023L01376:reg:6969080:p1
Version: federal_register_of_legislation:F2023L01376
Segment Type: reg
Provision Reference: reg 6969080 (pt 1/3)
Character Range: 67805–70929

6969080                              Mt Nebo           National Park      12.11.10          11–25     Very high

Macadamia tetraphylla (Rough-shelled bush nut)

Description
Macadamia tetraphylla is a perennial mid-storey evergreen subtropical rainforest tree to 18 m tall, with greyish-brown branchlets dotted with pale elongated lenticels (Hauser and Blok 1992). The simple oblong lanceolate leaves are usually arranged in whorls of four, 6–20 cm long and 2–4 cm wide. Blade tips are pointed, margins sharply serrated and petioles are 2–8 mm long (Stanley and Ross 2002). New leaves of M. tetraphylla are bright red in colour, whereas those of M. integrifolia are light green. Axillary pinkish purple flowers are arranged in brush-like hanging racemes 15–45 cm long. Compressed rounded fruits are greyish-green, 2–3.5 cm wide with a hard-inner rough surfaced shell protecting the edible kernel. Flowering period is August to September with fruit maturing and falling from March (Hauser and Blok 1992).

Life history and ecology
Little is known about the life history and ecology of this species. Pollination is thought to be principally carried out by native and European bees with seed dispersal by small rodents and gravity fall, probably with some assistance from local stream flooding. Pollen and seed dispersal leading to hybridisation has been observed between wild M. tetraphylla and cultivated M. integrifolia (O'Connor et al. 2015).
A study into the breeding system and fecundity of M. tetraphylla (Pisanu et al. 2009) found that the species had a low fruit to flower ratio and that the species was weakly self-compatible but incapable of self-pollination. Pisanu et al. (2009) identified a lack of light and competition with other more rapidly growing rainforest limits flower production, whilst insect pests and high seed predation, limits seed production and germination. An optimal outbreeding distance of 2 km was identified but the authors concluded that many wild populations do not have conspecifics at optimal distances owing to habitat fragmentation.
Macadamia tetraphylla has moderate to high genetic diversity recorded within the species and its populations, however, relatively low genetic differentiation between populations has been recorded at a regional scale (Peace 2005). Spain and Lowe (2011) investigated the genetics of six wild M. tetraphylla populations, finding a lack of genetic structure among adults. However, in the juvenile cohort, genetic differentiation and relatively high inbreeding scores were identified. The observed patterns were positively correlated with density of adult individuals consistent with the clumped distribution pattern of individuals commonly observed in small fragments (Pisanu 2001).
No information is available on the susceptibility of M. tetraphylla to fire, however, the known sensitivity of commercial Macadamias (O'Hare 2004), suggests application of the precautionary principle.

Distribution
Macadamia tetraphylla is endemic to eastern Australia, with a known national distribution of scattered populations extending from Mt Cotton south of Brisbane