Narrow-petalled Featherflower (Verticordia plumosa var. pleiobotrya) Interim Recovery Plan 2003-2008

Interim Recovery Plan no. 143
Robyn Phillimore and Rebecca Evans, July 2003
Department of Conservation and Land Management
Western Australian Threatened Species and Communities Unit (WATSCU)

1. Background

History

Verticordia plumosa var. pleiobotrya was named from the Greek pleio- (more than usual) and botrys (a bunch), in reference to the many small lateral groups of flowers. The first known collection of V. plumosa var. pleiobotrya, housed at the Western Australian Herbarium, was made in 1986 by A. and E. George, near Mundijong. An earlier collection was made from Geographe Bay but is undated (George 2002).

The taxon is thought to be rare due to extensive clearing of suitable habitat for urban development and agriculture. Once possibly occurring between Bullsbrook and Serpentine it now exists only in these two disjunct areas, within which the populations are severely fragmented. If the Geographe Bay record is correct, then the area of potential habitat is much greater. The largest most sustainable population, was, until recently, under significant threat. The owner of this private property had approval for development of this area and had begun subdividing the property to build houses. This area was purchased for conservation in 2002, however.

Numerous surveys for this taxon have been undertaken by staff from the Department's Swan Region and other botanists. However, very little of the winter wet habitat suitable for the taxon still exists in the known distribution, and the probability of finding new viable populations of the taxon is low. Also, the taxon is difficult to distinguish from the other varieties and has an ability to hybridise (Evans and Willers 2003). Nevertheless, a new population was discovered in 2000. A new population of this taxon may have also been discovered near Southern River on private property, but as access has not been permitted to the site, this population cannot be confirmed. Currently, Verticordia plumosa var. pleiobotrya is known from 7 populations consisting of around 5666 plants.

Description

Verticordia plumosa var. pleiobotrya A.S. George is a small shrub 30 to 60 cm tall and 30 to 45 cm wide. It has one to several stems arising from the base that openly branch. The leaves are mostly 4 to 8 mm long and slightly glaucous. Numerous groups of sweetly scented flowers occur on the short lateral branchlets. The peduncles are usually 1.5 to 3 mm long but can be to 8 mm. The hypanthium is 1.8 to 2.4 mm long. Sepals are 2.3 to 2.5 mm long with narrow lobes, and petals are 2 to 2.4 mm long and 1.1 to 1.5 mm wide (George 2002).

The taxon is distinguished from the other six varieties of plumed feather flowers (Verticordia plumosa) by its smaller flowers and narrower sepal lobes and petals. It is closely related to the Vasse Featherflower (Verticordia plumosa var. vassensis) differing in having more groups of flowers on short lateral branchlets (George 2002).

The Bullsbrook population (Population 5), and to a smaller extent at the Serpentine populations, are quickly becoming hybridised with Verticordia plumosa var. brachyphylla.

Distribution and habitat

Verticordia plumosa var. pleiobotrya is known from two areas, one in Bullsbrook north of Perth and the other in Mundijong, south of Perth. The taxon grows in grey sand, loam and clay on winter-wet flats, in low heath and open shrubland (George 2002). Four other taxa of Verticordias are also found with the Verticordia plumosa var. pleiobotrya including V. huegelii, V. densiflora var. densiflora, V. plumosa var. brachyphylla and V. pennigera.

The largest population (Population 6) of Verticordia plumosa var. pleiobotrya occurs within the threatened ecological community (TEC) the "Herb-rich shrublands in clay pans" (Swan Coastal Plain Community type 8 as described in Gibson et al. 1994) which is listed as Vulnerable in Western Australia. This community is dominated by Viminaria juncea and numerous herbs including Centrolepis aristata, Chorizandra enodis, Drosera menziesii subsp. menziesii, Drosera rosulata, Goodenia micrantha, Haemodorum simplex, Hyalosperma cotula and Schoenus odontocarpus. Adjacent to this community is the TEC "Eucalyptus calophylla - Kingia australis woodlands on heavy soils" (Swan Coastal Plain Community type 3a as described in Gibson et al. 1994). This TEC is listed as Critically Endangered in Western Australia and Endangered under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). This location has been recognised as a Bush Forever site (Number 65), and purchased for conservation, because it is an area of 'regional significance bushland to be retained and protected forever' (State of Western Australia 2000).

Also Population 5 of Verticordia plumosa var. pleiobotrya occurs within the TEC "Herb-rich saline shrublands in clay pans, Swan Coastal Plain Community type 7, Gibson et al. 1994" (listed as Vulnerable in Western Australia) threatened ecological community. This community is dominated by Melaleuca viminea and numerous herbs including Brachyscome bellidioides, Centrolepis polygyna, Goodenia micrantha, Pogonolepis stricta, Polypompholyx multiflora, Schoenus odontocarpus and Siloxerus humifusus. This location has also been recognised as a Bush Forever site (Number 292) because it is an area of 'regional significance bushland to be retained and protected forever' (State of Western Australia 2000).

Habitat critical to the survival of the species, and important populations

Given that this taxon is listed as threatened it is considered that all known habitat is habitat critical. In addition all populations, are considered important to the survival of the taxon. Recovery actions include survey for further populations that would lead to the identification of additional habitat critical. The largest populations are numbers 2 and 6, and these are considered particularly significant for the taxon's continued existence.

Benefits to other species/ecological communities

Populations 5 and 6 are also located within occurrences of two Threatened Ecological Communities (TECs) (English and Blyth 1997). Gibson et al. (1994) describe the communities as 'Herb-rich shrublands in clay pans' and 'Herb-rich saline shrublands in clay pans'. Recovery actions implemented to improve the quality or security of the habitat of Populations 5 and 6 of Verticordia plumosa var. pleiobotrya are likely to improve the status of the TECs in which these populations are located.

International Obligations

This plan is fully consistent with the aims and recommendations of the Convention on Biological Diversity, ratified by Australia in June 1993, and will assist in implementing Australia's responsibilities under that Convention. However, as Verticordia plumosa var. pleiobotrya is not listed under any international agreement, the implementation of other international environmental responsibilities is not affected by this plan.

Role and interests of indigenous people

There are no known indigenous communities interested or involved in the management of areas affected by this plan. Therefore no role has been identified for indigenous communities in the recovery of this taxon.

Social and economic impacts

The implementation of this recovery plan has the potential to have some limited social and economic impact, as some populations are located on private property. Areas on private land that are considered to be 'habitat critical' may be regarded as having potential for uses other than conservation by landholders. Approaches that may minimise this potential impact could include covenants, management agreements or land acquisition.

Evaluation of the Plans Performance

The Department of Conservation and Land Management, in conjunction with the Swan Region Threatened Flora and Communities Recovery Team will evaluate the performance of this Interim Recovery Plan. The plan is to be reviewed within five years of its implementation. Any changes to management / recovery actions will be documented accordingly.

Critical habitat

Critical habitat is habitat identified as being critical to the survival of a listed threatened species or listed threatened ecological community. Habitat is defined as the biophysical medium or media occupied (continuously, periodically or occasionally) by an organism or group of organisms or once occupied (continuously, periodically or occasionally) by an organism, or group of organisms, and into which organisms of that kind have the potential to be reintroduced (Environment Protection and Biodiversity Conservation Act 1999).

The critical habitat for Verticordia plumosa var. pleiobotrya comprises:

  • the area of occupancy of known populations;
  • areas of similar habitat within 200 metres of known populations, ie. grey sand, loam and clay on winter-wet flats, in low heath and open shrubland (these provide potential habitat for natural range extension);
  • remnant vegetation that surrounds and links several populations (this is necessary to allow pollinators to move between populations);
  • additional occurrences of similar habitat that do not currently contain the taxon but may have done so in the past (these represent possible translocation sites); and
  • the local catchment for the surface and possibly ground waters that maintain the winter-wet habitat of the taxon (it occurs on clay flats that are seasonally inundated and depend on the local hydrology).

Biology and ecology

The genus Verticordia is well known for its colourful, showy flowers and most taxa in the genus have horticultural potential. Few species have proved reliable in cultivation, however, and frequently a large percentage of seed is infertile and germination is low (Wrigley and Fagg 1979). Most species make excellent cut flowers and a considerable market has been established (Leigh et al. 1984).

Propagation of Verticordias has been mainly from cuttings with a few grown from seed. In general, Verticordias produce only one seed per flower in the wild. Germination occurs from within old flowers that have fallen to the ground. Research by the Department's Threatened Flora Seed Centre (TFSC) has shown that seed set is generally low in Verticordias (less than 51%) and is variable between species, within the same species in different locations, and in different years at the same location (Cochrane and McChesney 1995). The taxon has successfully been cultivated from cuttings by local enthusiasts (personal communication N. Skade ¹).

Verticordias are generally considered to be fire sensitive with post-fire regeneration occurring mainly from seed. They grow relatively rapidly and are often at their most floriferous stage within five years (George 2002).

Threats

Verticordia plumosa var. pleiobotrya was declared as Rare Flora and ranked as Critically Endangered (CR) in September 2000 under the Western Australian Wildlife Conservation Act 1950. It is also listed as Endangered under the EPBC Act. It currently meets World Conservation Union (IUCN 2000) Red List Category Vulnerable (VU) under criteria B1ab(iii,v)+2ab(iii,v) due to the severe fragmentation of populations, and a continuing decline in the quality of habitat and the number of plants. The level of threat to the taxon has declined recently as a consequence of the acquisition of the property that contains the largest population for conservation, and other recovery actions. The main threats are weed invasion, drainage channel maintenance, salinisation, road, track and firebreak maintenance, grazing, crushing, degraded habitat, poor regeneration, rabbits, inappropriate fire regimes and dieback disease.

  • Weed invasion is a major threat to all populations. At Population 2 the major weeds include Babiana angustifolia and other grasses; at Subpopulations 6a and 6b Watsonia sp. and Eragrostis curvula (African Lovegrass), at Subpopulations 6c and 6d Leptospermum laevigatum (Victorian tea-tree) and E. curvula. Weeds suppress early plant growth by competing for soil moisture, nutrients and light. They also exacerbate grazing pressure and increase the fire hazard due to the easy ignition of high fuel loads, which are produced annually by many weed species.
  • Drainage channel maintenance is a major threat to Populations 1 and 3, and Subpopulations 6d and 7a. Drainage channels run parallel through the road reserves that contain Verticordia plumosa var. pleiobotrya. Maintenance may include scouring of the channel to alleviate flooding of agricultural lands and the existing road. This disturbs or destroys the vegetation and has the potential to exacerbate weed invasion into the narrow road reserve.
  • Salinisation is a result of a rise in the water table due to widespread clearing of deep rooted vegetation. This leads to degradation of the taxon's habitat. If not addressed, this decline will continue in the medium to long term.
  • Road, track and firebreak maintenance activities threaten most populations. Threats include grading, chemical spraying, construction of drainage channels and the mowing of roadside vegetation. Several of these actions also encourage weed invasion.
  • Grazing by horses is a major threat to Subpopulation 7b on private property, and the plants located along the fenceline on the road reserve at Subpopulation 7a. Apart from being subject to grazing, increased nutrient levels from droppings are resulting in the proliferation of weeds, and trampling of vegetation is impacting on the habitat of the taxon. Grazing may also have an impact on the establishment of Verticordia plumosa var. pleiobotrya seedlings thereby limiting the natural recruitment of the taxon.
  • Crushing by vehicles is a threat to plants at Population 5. In the process of illegally driving through the reserve after accessing the site from the main road, vehicles are crushing the Verticordia plumosa var. pleiobotrya plants.
  • Degraded habitat: Subpopulation 7b of Verticordia plumosa var. pleiobotrya occurs on private property which is quite degraded and has little associated native vegetation to support pollinators and seed dispersers.
  • Poor regeneration, due to lack of appropriate disturbance threatens most populations as very few young plants of Verticordia plumosa var. pleiobotrya have been observed, with the exception of Population 6 where some seedlings occur.
  • Rabbits (Oryctolagus cuniculus) are present throughout Populations 5 and 6 and although there is no evidence that the Verticordia plumosa var. pleiobotrya is being grazed, rabbits are impacting on the habitat by causing soil disturbance. Increased nutrient levels in the soil from rabbit droppings may also occur, and result in increased weed invasion. Grazing is most likely to have an impact on the establishment of young shoots of V. plumosa var. pleiobotrya thereby limiting natural recruitment.
  • Inappropriate fire regimes may affect the viability of populations of Verticordia plumosa var. pleiobotrya. The fire response of the taxon is not known, but, verticordias are generally considered to be fire sensitive, with post fire regeneration occurring mainly from seed. Too frequent fire is likely to destroy the populations before regenerating or juvenile plants reach maturity and replenish the soil seed bank; however, occasional fires or other disturbances are likely to be required for the taxon to propagate from soil stored seed.
  • Dieback disease is a potential threat to populations of Verticordia plumosa var. pleiobotrya. Dieback caused by the plant pathogen Phytophthora spp. causes the roots to rot and results in susceptible plants dying of drought stress. Many species of Verticordia are susceptible to the disease, and it seems likely that Verticordia plumosa var. pleiobotrya is susceptible. The habitat is susceptible and there are signs of infestation at Populations 2 and 5.
Summary of population information and threats
Pop. No. & Location Land Status Year/No. plants Condition Threats
1. Mundijong (S) Shire Road Reserve 1999 0
2002 0
Poor Road and drain maintenance, weeds, inappropriate fire regimes, salinisation, poor regeneration, dieback
2. Mundijong (S) Shire Road Reserve 1995 500+
1999 323 (3)
2002 315 [50 dead]
Moderate Road maintenance, weeds, inappropriate fire regimes, salinisation, poor regeneration, dieback
3. Mundijong (S) Shire Road Reserve 1999 0
2002 0
Poor Road and drain maintenance, weeds, inappropriate fire regimes, salinisation, poor regeneration, dieback
4. Serpentine (PH) Shire Cemetery 1994 1
1999 1
2001 1
2002 1
Moderate/ Poor Weeds, inappropriate fire regimes, salinisation, poor regeneration, dieback
5. Bullsbrook (PH) Nature Reserve 1992 1
1999 13 (54)[1 dead]
Healthy Salinisation, road maintenance, rabbits, inappropriate fire regimes, dieback, crushing
6A. Byford (S) Private Property (being transferred to State Planning Commission) 1998 200
1999 2974 [10 dead]
Moderate Firebreak maintenance, rabbits, weeds, inappropriate fire regimes, salinisation, poor regeneration, dieback
6B. Byford (S) Private Property (being transferred to State Planning Commission) 1999 2301 [5 dead] Moderate Weeds, rabbits, firebreak maintenance, inappropriate fire regimes, salinity, poor regeneration, dieback
6C. Byford (S) Shire Road Reserve 1999 39
2002 19
Moderate/ Poor Road maintenance, weeds, inappropriate fire regimes, salinisation, poor regeneration, dieback
6D. Byford (S) Shire Drain Reserve 1999 26+
2002 4
Poor Weeds, drain maintenance, road and firebreak maintenance, inappropriate fire regimes, salinisation, poor regeneration, dieback
7A. Mundijong (S) Shire Drain Reserve 2000 *30
2001 *65
2002 29
Poor Drain maintenance, grazing, road maintenance, weeds, inappropriate fire regimes, salinity, poor regeneration, dieback
7B. Mundijong (S) Private Property 2000 *30
2001 *65
2002 ~10
Poor Grazing, weeds, firebreak maintenance, inappropriate fire regimes, salinity, degraded habitat, poor regeneration, dieback

PH = Perth Hills District, S = Swan Coastal District
Numbers in brackets = number of seedlings.
* = total for subpopulations combined.

Guide for decision-makers

Section 1 provides details of current and possible future threats. Developments in the immediate vicinity of the population or within the defined critical habitat of Verticordia plumosa var. pleiobotrya require assessment. No developments should be approved unless the proponents can demonstrate that they will have no significant impact on the taxon, or its habitat or potential habitat, or the local surface and possibly ground water hydrology.