Title: Billardiera heterophylla L.Cayzer & Crisp (Lindl.)

Scientific Name:

Billardiera heterophylla L.Cayzer & Crisp (Lindl.)

Common Name:

bluebell creeper



Source & more images (via ALA)

Status: A revision of Billardiera and other closely related genera has been recently undertaken by Cayzer et al (2006). Analyses indicated that the genus Billardiera should incorporate Sollya, and the former species Sollya heterophylla has been reclassified as two species Billardiera heterophylla and Billardiera fusiformis. Due to the recent revision, most literature does not distinguish between the two species.

Habitat: Can invade forest, woodland, grassland, scrub, thicket, heathland, and riparian and coastal communities, (Carr et al 1992, White 2007) where annual rainfall exceeds 700 mm. There
are major infestations in coastal areas of southern Victoria (Muyt 2001). In addition, it is also described as readily colonizing disturbed sites, and in its native Western Australia, B. heterophylla occurs around inland salt lakes but B. fusiformis does not appear to grow well in saline areas (Cayzer et al. 2004).

Distribution:

Present Distribution - Australia (source: ALA)




Invasiveness Assessment

ESTABLISHMENT


1. Germination requirements? Taylor (1997) showed highest seed germination at 15oC and no germination occurring at 25oC, which corresponds to temperatures in the field when rainfall at is highest, indicating a requirement of natural seasonal disturbances for germination.

2. Establishment requirements? Can grow in part shade (Blood 2001) and known to invade several forest communities (Carr et al 1992). Could establish under moderate canopy cover.

3. How much disturbance is required? ‘Able to invade otherwise intact native vegetation (NCSSA 2004)’ and areas that are ‘relatively weed free and stable are proving to be still quite susceptible to invasion (Hill 1997)’. Appears able to establish in healthy natural ecosystems, such as heathland (Carr et al 1992, White 2007).

GROWTH / COMPETITIVE


4. Life form? 'Twining climber or dense scrambling shrub' (Muyt 2001).

5. Allelopathic properties? Nothing grows under canopies and this is likely due to allelopathy (R. Adair pers.com.).

6. Tolerates herb pressure? Although it is documented not to mature in regularly grazed pasture (White 2007), Taylor (1997) found that in natural ecosystems herbivore damage of plants was extremely low. Consumed but not preferred.

7. Normal growth rate? Although seedlings are described as initially slow growing as an extensive root system forms (Blood 2001) it is otherwise documented as growing rapidly (Blood 2001, Strickland 1990) especially after fire (R. Adair pers. comm., Muyt 2001). Overall available information suggests at least a moderately rapid growth rate.

8. Stress tolerance to frost, drought, w/logg, sal. etc? Tolerant of drought, frost to -5oC (Blood 2001) and in WA (B. heterophylla) inhabits saline soils and occurs around inland salt lakes (Cayzer et al 2004). Although most established plants are killed by hot fire, low intensity fires enhance invasion (Taylor 1997) and fire triggers germination and rapid growth (White 2007, Muyt 2001).
Highly tolerant of at least two stresses. Tolerance to water logging not found documented.

REPRODUCTION


9. Reproductive system? Reproduction is by seed and regeneration from root segments (Blood 2001).

10. Number of propagules produced? Fruits contain up to 80 seeds (Taylor 1997). Images indicate that a single plant could produce above 2000 propagules.

11. Propagule longevity? 'Seeds are reported to remain viable for at least 5 years although this requires confirmation' (Hill 1997).

12. Reproductive period? Has the ability to convert large areas to a near monoculture (Hill 1997) with large colonies many metres across being formed purely by vegetative means (Blood 2001). Potential to form self-sustaining monocultures.

13. Time to reproductive maturity? Rapid growth following fire initiates flowering and fruiting within 12-24 months (White 2007). Produces propagules between 1-2 years after germination.

DISPERSAL


14. Number of mechanisms? Spread by birds, animals including foxes and dumped garden waste (Blood 2001).

15. How far do they disperse? Its spread by birds and foxes (Blood 2001) is likely to disperse some seeds greater than 1km.


Impact Assessment

RECREATION


1. Restrict human access? ‘Blue-bell creeper scrambles to head height on middle storey plants forming an almost impenetrable barrier that is difficult to treat or transverse with equipment' (Hill 1997). High nuisance value, people access with difficulty.

2. Reduce tourism? ‘Blue-bell creeper scrambles to head height on middle storey plants forming an almost impenetrable barrier that is difficult to treat or transverse with equipment' (Hill 1997). There is a possibility of it having a minor affect on recreational use if it grew across walking paths. It is also described as forming large colonies (Blood 2001), that could impact on the aesthetics of an area.

3. Injurious to people? ‘It contains toxins, which can cause skin irritation and nausea, so it is important that gloves are worn when handling’. Mildly toxic

4. Damage to cultural sites? Though not specifically documented, as a climbing species that can reach up to 4 metres in height (DNRE 2002), there is potential for it to have a moderate visual affect on the aesthetics of a cultural site or infrastructure.

ABIOTIC


5. Impact flow? As a terrestrial species it is unlikely to impact on water flow.

6. Impact water quality? As a terrestrial species it is unlikely to impact on water quality.

7. Increase soil erosion? ‘It affects sites on slopes and with loss of biodiversity as a result of invasion this could lead to increased erosion risks e.g. at Arthur’s seat (R. Adair pers. com.)’. Its ability to smother and eliminate other vegetation (Muyt 2001, DNRE 1997) particularly those with extensive root systems, could lead to an increase in soil erosion, especially as it often inhabits coastal areas (Muyt 2001). It has the potential to impact on erosion but the extent of its impact is unclear.

8. Reduce biomass? Appears to increase biomass in communities due to development of heavily tangled shrub layer (R. Adair pers. com.).

9. Change fire regime? ‘Likely to increase fire risk due to increase in fine fuel loads (R. Adair pers. com.)’. This species invades many diverse ecosystems with varying fire regimes. An increase in fine fuel loads could cause a moderate change to both fire frequency and intensity. For example in a ‘shrubby wet forest’ habitat (White 2007), it could moderately increase fire frequency but decrease fire intensity.

COMMUNITY HABITAT


10(a) Impact on composition of high value EVC? Large colonies many metres across can be formed (Blood 2001) and isolated plants can develop into aggressive invading fronts that smother all vegetation in their path, forming virtual monocultures (Taylor 1997, Hill 1997).

10(b) Impact on medium value EVC? Large colonies many metres across can be formed (Blood 2001) and isolated plants can develop into aggressive invading fronts that smother all vegetation in their path, forming virtual monocultures (Taylor 1997, Hill 1997).

10(c) Impact on low value EVC? Large colonies many metres across can be formed (Blood 2001) and isolated plants can develop into aggressive invading fronts that smother all vegetation in their path, forming virtual monocultures (Taylor 1997, Hill 1997).

11. Impact on structure? Large colonies many metres across can be formed (Blood 2001) and isolated plants can develop into aggressive invading fronts that smother all vegetation in their path, forming virtual monocultures (Taylor 1997, Hill 1997).
Can impact on all strata including tree stratum due to lower availability of niches for seedling establishment (R. Adair pers.com.).

12. Effect on threatened flora? White (1997) identified 45 flora taxa that are threatened by habitat alteration as a result of invasion through direct competition for regeneration sites, light, water and space. However, no description of its specific impact on individual threatened flora species was documented.

FAUNA


13. Effect on threatened fauna? White (1997) identified 16 fauna taxa that are threatened by habitat alteration as a result of invasion, due to structural degradation, changed fire regimes, trophic disintegration, and loss of prey or food plants. However, no description of its impact on specific threatened fauna taxa was documented.

14. Effect on non-threatened fauna? White (1997) identifies that habitat alteration as a result of invasion threatens fauna, through structural degradation, changed fire regimes, trophic disintegration, and loss of prey or food plants. Reduction in habitat and food source would likely lead to a reduction in the number of individuals in a population.

15. Benefits fauna? ‘A range of fauna including frugivorous birds, mammals and possibly reptiles (Bachmann and Johnson in prep) disperse seeds' (White 2007). Likely to provide some assistance as a food source to desirable fauna species.

16. Injurious to fauna? No reference was found in the literature to suggest that this species possesses any properties injurious to fauna.

PEST ANIMAL


17. Food source to pests? Foxes are described as a seed disperser (Blood 2001, White 2007). Provides food to one serious pest species.

18. Provides harbor? The nature of its habit suggests it is unlikely to provide harbour for serious pests like rabbits or foxes, and no information was found documented to indicate that it provides harbour for any minor pest species.

AGRICULTURE


19. Impact yield? B. heterophylla is not described as a weed of agriculture.

20. Impact quality? B. heterophylla is not described as a weed of agriculture.

21. Affect land values? B. heterophylla is not described as a weed of agriculture.

22. Change land use? B. heterophylla is not described as a weed of agriculture.

23. Increase harvest costs? B. heterophylla is not described as a weed of agriculture.

24. Disease host/vector? B. heterophylla is not described as a weed of agriculture.




Feedback

Do you have additional information about this plant that will improve the quality of the assessment? If so,we would value your contribution.


Assessment ratings originally made by the Victorian Department of Primary Industries.
The entry of this assessment was made possible through the generous support of f Dr Robin Adair, Research Leader, Weed Sciences, Victorian Department of Primary Industries.






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Date: 2 December 2011; 1:46:32 PM AEDT

Author Name: David Low
Author ID: adminDavid