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Conserving threatened species in Western Sydney

The Threatened Flora Propagation Program (TFPP) was created to develop the most effective approaches to the propagation and translocation of three threatened native plant populations affected by the development of the Western Sydney International (Nancy-Bird Walton) Airport. 

Project background and species profile

The Western Sydney Unit, Department of Infrastructure, Transport, Regional Development and Communications, and GHD oversaw the implementation of the TFPP by the Australian Botanic Garden Mount Annan. The aim was to develop the most effective approaches to the propagation and translocation of threatened native plant populations affected by the development of the Western Sydney International (Nancy-Bird Walton) Airport at Badgerys Creek. 

TFPP focused on three listed threatened species: Pultenaea parviflora (a shrub), Marsdenia viridiflora subsp. viridiflora (a climber) and Pimelea spicata (a low shrub). Importantly, the project has featured an integration of the Garden's horticultural and scientific skills, resulting in seed collections, germination and propagation experiments, establishment of nursery stock and genetic analysis. This is a significant advance on the existing horticultural and conservation knowledge of these poorly known threatened species.

Download a pdf copy of the Western Sydney International (Nancy-Bird Walton) Airport Threatened Flora Propagation Program Delivery Report (2019) and the Conservation genomics of Pimelea spicata report (2019) or view a summary of the species profile and main research findings further below. 

Pimelea spicata

Pimelea spicata is a low spreading shrub growing to 50 cm in height. Leaves are opposite and elliptical, about 20 mm long by 8 mm wide. Tubular flowers are white, pink-tinged up to 10 mm long, with four spreading petals. The species flowers sporadically throughout the year, with good flowering often observed during summer, particularly after heavy rain and good soil moisture. The main distribution is the Cumberland Plain region of Western Sydney, with some disjunct populations in the Illawarra region.

Marsdenia viridiflora subsp. viridiflora

Marsdenia viridiflora subsp. viridiflora is a twining climber with flowers that are greenish yellow, bell-shaped and in clusters of 3-10. Fruit are large and pear-shaped, up to 80mm long, producing seeds with a silky coma  Seed production in wild populations is limited and highly variable. It is widely distributed throughout coastal and inland regions of NSW and Queensland. The species is highly restricted in the Cumberland Plain region of Western Sydney, where some endagered populations. 

Pultenaea parviflora

Pultenaea parviflora is a small erect shrub that grows between 1-1.8m high and is listed as an endagered species. It produces yellow pea-like flowers and seeds are generally produced in December, which are egg shaped up to 5mm long. Seeds have a hard coat and can be readily dried and stored long term in a seedbank. Distribution is restricted to the Cumberland Plain region in the western districts of Sydney. 

Propagation and germination research 

The main focus has been collection of live cutting material from the Western Sydney International (Nancy-Bird Walton) Airport site to produce plants for conservation collections at the Australian Botanic Garden Mount Annan Nursery. As a backup to these live collections, seed will also be stored at The Australian PlantBank, which is the award-winning home of plant conservation research, germplasm collection and storage in NSW at Mount Annan. Our seed, potted collections and tissue culture collections provide an insurance policy against extinction of native plants in the wild.
 

Pultenaea parviflora

  • Over 400 plants grown in the Nursery from seed and 6,100 seeds held at the Australian PlantBank
Pultenaea parviflora is a straightforward plant to propagate from seed and grow under nursery conditions. Cuttings had a low success rate and produced plants with low vigour. Seed can be collected easily using mesh bags, and the hard coated seed has a very long storage life under good storage conditions.
 

Marsdenia viridiflora subsp. viridiflora

  • Over 500 plants grown in the Nursery from cuttings and 108 seeds held at the Australian PlantBank​
  • An ex-situ potted collection is being established and will be held in the Nursery
Marsdenia viridiflora subsp. viridiflora produces small amounts of fruit/seed, making good quantity seed collections difficult. Germination and storage of seed is straightforward. Cuttings is the preferred method to produce plants, although they are slow to establish.
 

Pimelea spicata

  • Over 500 plants grown in the Nursery from cutting and seed, and 5400 seeds held in long term storage at the Australian PlantBank​​
Pimelea spicata is a difficult species to propagate and to collect seed from in quantity, particularly during drought conditions. Seed germination rates are low due to physiological dormancy, although treatment with gibberellic acid and smoke water improved germination. Cuttings are slow to establish, and even with well struck cuttings losses at the potting stage can be significant.
Thermogradient table experiments
A thermogradient table allows simultaneous testing of multiple seed samples across a range of temperature combinations to determine the optimum, upper and lower limits of germination.
Pultenaea parviflora
Pultenaea parviflora successfully growing in the Nursery at the Australian Botanic Garden Mount Annan. 

Pimelea spicata genomics research 

Loss of genetic diversity can reduce the genetic health of an organism, and as a result, increase the risk of local extinction. The genetic diversity of populations across the known distribution of Pimelea spicata was measured using high quality genome scans. 

A total 282 Pimelea spicata individuals were sampled across the extent of the known range. This genetic data will guide ex situ conservation collections and translocation at the Western Sydney International (Nancy-Bird Walton) Airport site. This research provides for the very first time an important regional genetic perspective for this threatened species. It also provides an understanding of genetic health, population structure and genetic diversity patterns to support long term conservation and management. 

Surprisingly, the most northern and the most southern sites of P. spicata are genetically most similar, and are differentiated from the rest of P. spicata populations that exist on the Cumberland plain. Our Environmental Niche Models suggest P. spicata has very little environmental suitability beyond its currently known distribution, and under future climatic projections suitable environments might be further constrained to the southern Cumberland plains.

Pimelea spicata
Attaching bags to Pimelea spicata plants to collect seeds
Pimelea spicata
Succesful collection of Pimelea spicata seeds being prepared for research and storage at the Australian PlantBank 

Future outlook

Most of the plants are likely to be used in revegetation programs to help maintain the population size and genetic viability of the regional populations of these species. A subset of the tube stock plants could be used to establish a longer-term potted ex situ collection at the Nursery at the Australian Botanic Garden Mount Annan. 

Information on the species’ ecology and propagation is in the public domain,
representing a significant indirect offset outcome for the Biodiversity Offset Delivery Plan, and an improvement in our knowledge for these species, which are considered by restoration practitioners as difficult to propagate.