Department of Environment and Conservation (NSW), 2005
ISBN: 1 7412 2144 7
6 Biology and Ecology
- 6.1 Habit and longevity
- 6.2 Reproductive biology
- 6.3 Population size and structure
- 6.4 Response to disturbance
- 6.5 Fire ecology
D. sp. C Illawarra is a medium sized rainforest tree that grows to 20 metres and is capable of prolific suckering. The longevity of the species is not known although, given its clonal nature and the large size of some individuals, it is believed to be a long-lived species.
- 6.2.1 Vegetative reproduction
- 6.2.2 Breeding system
- 6.2.3 Phenology
- 6.2.4 Fruit production
- 6.2.5 Seed Ecology
D. sp. C Illawarra is capable of vegetative reproduction from stems (coppicing) and underground rhizomes (suckering) (M. Bremner, DEC, pers. comm.).
D. sp. C Illawarra flowers are morphologically hermaphrodite, having both male and female organs present in each flower (Foreman & Whiffin MS). It is not known whether the species is capable of self- pollination.
The pollination mechanisms of the species are unknown and consequently, so is the potential role that pollen vectors may play in the transfer of genetic material within and between sites. However, the predominant means of reproduction in D. sp. C Illawarra appears to be asexual.
D. sp. C Illawarra flowers briefly in September and early October although not all populations or individuals appear to flower each year (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.). This is not uncommon behaviour amongst rainforest understorey species however as limited resources can restrict the flowering of these species to good seasons or at specific intervals (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.).
Table 6 shows the flowering activity at 11 sites that were surveyed during the flowering period of the species.
|Site Code||Total Stems||Flowering Stems|
While ten of these sites contained flowering stems, the proportion of stems that were flowering was generally very low and only two sites (Dc7 and Dc8) contained stems that could be described as flowering heavily (M. Bremner, DEC, pers. comm.). Whether such low levels of flowering activity is a natural response to limited resources or an indication of a lack of fitness is considered to be a critical aspect of the species biology that requires investigation.
D. sp. C Illawarra plants propagated from seed take approximately six years to flower in cultivation (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.).
The fruit of Daphnandra spp consist of numerous hairy achenes (ie dry, indehiscent, 1-seeded fruit) that are enclosed within a fruiting receptacle. This receptacle enlarges, becomes woody and dehisces through a single slit upon maturity (Harden 1990).
The period of time that is required for the fruit of D. sp. C Illawarra to mature is unclear. Harden (1990) states that the fruit of Daphnandra spp develop over six to eight months while Foreman & Whiffin (MS) describe the fruiting period for D. sp. C Illawarra as August. It is likely however that the fruit of D. sp. C Illawarra matures over 10 to 12 months, with the fruiting receptacle splitting to release the achenes (fruit) between July and September (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.).
Low levels of seed production in D. sp. C Illawarra are suspected. Most sites appear to only produce pseudo-fruit, deformed fruiting receptacles that are roughly globose in shape and contain no seeds (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.). It is unknown whether the production of pseudo-fruit is a consequence of seed predation, naturally low pollen viability, inbreeding depression, self-incompatibility, the absence of pollinators or some other factor.
Typical fruiting receptacles have been observed at just two sites, Willow Creek (Dc14) and Actephila Gully (Dc21) (A. Bofeldt, Wollongong Botanic Gardens, pers. comm; M. Mulvaney, DEC, pers. comm.). The fruit collected from Dc14 was found to contain viable seed while no fruit has been collected from Dc21 to date.
The extent to which the species produces viable seed and the factors responsible for the production of pseudo-fruit are essential aspects of the species biology requiring investigation.
Aspects of the seed ecology of D. sp. C Illawarra are poorly understood. The morphology of the seeds (ie small with long hairs) indicates that the primary seed dispersal mechanism is likely to be wind.
In germination trials, between 30 and 50 per cent of seed collected from Dc14 germinated within two months without any special treatment (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.).
Further investigation of the viability and longevity of D. sp. C Illawarra seed will assist future management of the species.
As a consequence of the highly clonal nature of D. sp. C Illawarra, it is not possible to determine the number of genetic individuals (genets) that are present at a site without genetic analysis. However, an indication of the number of genets present can be inferred from the number and size of stems (ramets) present and the area occupied by those stems.
Table 7 details the area of occupancy and the number of stems (ramets) present at 16 D. sp. C Illawarra sites. Less than 20 stems are present at seven of these sites and nine sites have an area of occupancy of less than 400 m2. From this data it is assumed that the total population size of D. sp. C Illawarra is small. It is likely that some sites contain just one genetic individual.
D. sp. C Illawarra is capable of suckering from underground rhizomes and coppicing from damaged stems in response to physical disturbance. Extensive suckering was evident at the majority of sites that were surveyed during the preparation of this plan. This suckering is considered to be at least partially attributable to natural disturbances associated with the movement of unconsolidated rock material on steep unstable slopes.
Many of the vegetation remnants occupied by D. sp. C Illawarra have been partially cleared and/or grazed in the past, and it is likely that the species survived these disturbances by suckering and/or coppicing from damaged stems. However, the clearing or grazing of D. sp. C Illawarra sites is clearly not desirable as, in addition to physically damaging plants, these activities will modify the closed forest habitat of the species and contribute to its degradation.
As D. sp. C Illawarra is a climax rainforest species, it is unlikely that disturbance is required to facilitate seedling recruitment (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.).
|Site Code||Area (sq. m.)||Total Stems||Stems <0.3 m||Stems 0.3 to 2 m||Stems 2 to 5 m||Stems >5m|
|Dc1||200||8||-||2 (26%)||3 (37%)||3 (27%)|
|Dc2||1000||109||3 (3%)||38 (35%)||37 (34%)||31 (28%)|
|Dc3||1570||90||5 (6%)||21 (23%)||39 (43%)||25 (28%)|
|Dc7||5800||2560*||Not recorded||Not recorded||338 (13%)||100 (4%)|
|Dc10||1420||>1000*||Not recorded||Not recorded||212 (21%)||90 (9%)|
|Dc11||20||12||5 (45%)||5 (45%)||1 (10%)||-|
|Dc12||3900||1200*||Not recorded||Not recorded||138 (11%)||17 (1%)|
|Dc13||100||26||2 (8%)||10 (38%)||14 (54%)||-|
|Dc14||600||168||16 (10%)||76 (45%)||54 (32%)||22 (13%)|
|Dc15||100||15||-||4 (27%)||8 (53%)||3 (20%)|
|Dc16||200||18||6 (33%)||8 (44%)||1 (6%)||3 (17%)|
|Dc17||350||105||6 (6%)||84 (80%)||12 (11%)||3 (3%)|
|Dc21||100||11||-||3 (27%)||8 (73%)||-|
|Dc27||1600||64||6 (9%)||32 (50%)||15 (23%)||11 (18%)|
|Dc33||3250||391||31 (8%)||313 (80%)||43 (11%)||4 (1%)|
|Dc40||1200||335||17 (5%)||271 (81%)||32 (10%)||15 (4%)|
|Dc41||400||237||51 (21%)||170 (72%)||12 (5%)||4 (2%)|
There have been no direct observations of the effects of fire frequency, intensity or seasonality on D. sp. C Illawarra. Given its rainforest habitat, the species is unlikely to have evolved with fire and as such, fire is considered likely to impact negatively upon the lifecycle of the species. Such impacts may result from physical damage to individual plants or from changes to its habitat.