One-Headed Smokebush Conospermum densiflorum subsp. unicephelatum Interim Recovery Plan 2004-2009)

Western Australian Threatened Species and Communities Unit (WATSCU)
© The Western Australian, Department of Conservation and Land Management, 2004

1. Background

History

Conospermum densiflorum subsp. unicephalatum was first collected by William Blackwell in 1932 "near Gingin between Midland and Moora" and recollected in 1974 and 1975. All other previous herbarium collections except for one on the Great Northern Highway have been relocated in recent surveys.

Conospermum densiflorum subsp. unicephalatum is currently known from five populations on the road and rail verge within a 10km stretch near Gillingarra between Mogumber and Moora. It is known from a total of 295 adult and 886 juvenile plants.

Description

Conospermum densiflorum subsp. unicephalatum is a conspicuous plant when flowering, and is an erect perennial shrub to 0.6 m tall. The stems and foliage have long, spreading hairs. The leaves are crowded, filiform, ca. 30-40 mm long, with white, spreading hairs. The peduncle is leafless, with a single, almost globular, head-like inflorescence which is 1.5 cm in diameter. The floral bracts are slender and hairy and as long as the flowers. The flowers are tubular and two-lipped, ca. 10 mm long and bluish-white in colour (Patrick and Brown 2001).

Conospermum densiflorum subsp. unicephalatum differs from C. densiflorum subsp. densiflorum in that it has a single head of flowers on each scape, rather than several (up to 10) heads forming a compact corymb (Brown et al. 1998).

Distribution and habitat

Conospermum densiflorum subsp. unicephalatum is restricted to low lying sandy clay soils with surface lateritic gravel, in an area between Gingin and Moora over a range of about 10 km. A previous collection in 1974, which has not been relocated, extends this range to 35km. Generally the plants are healthy, although the surrounding habitat is quite disturbed. Habitat consists of heathland of Acacia acuminata, A. puchella, Adenanthos cygnorum, Allocasuarina campestris, Austrostipa elegantissima, Daviesia preissii, Dryandra serratulioides subsp. serratulioides (DRF taxon ranked as Vulnerable), Conostylis setigera, Calothamnus pachystachyus (Priority 4), Glischrocaryon aureum, Hibbertia sp., Labichea lanceolata, Melaleuca sp., Ptilotus sp. and Verticordia sp.

Conospermum densiflorum subsp. unicephalatum appears to be a disturbance opportunist as new seedlings are often located following disturbances such as gravel extraction.

Biology and ecology

Very little is known about the biology and ecology of the genus Conospermum. Most Conospermums are insect pollinated by either native bees or flies which trigger the explosive mechanism in the flower. Although copious amounts of fruit are produced, the amount of viable seed is low. Propagation of Conospermum by cuttings is difficult (Sainsbury 1991). In May 2001, one batch of 14 cuttings of Conospermum densiflorum subsp. unicephalatum cuttings was planted by BGPA, but these did not strike (A. Shade pers. comm. Amanda Shade, Horticulturalist, Botanic Garden and Parks Authority). Conospermum seedlings generally develop a tap root (Sainsbury 1991).

Initial germination rates from untreated seed trials have been variable, ranging from 16-67% (A. Crawford unpublished data Andrew Crawford, Senior Technical Officer, CALMs Threatened Flora Seed Centre).

Conospermum densiflorum subsp. unicephalatum appears to be a disturbance opportunist, with germination apparently stimulated by soil disturbance where gravel has been extracted. Response to fire is unknown, but as it is a seeder, the plants are likely to be killed by fire, and then germinate from soil stored seed.

Dieback testing for resistance to Phytophthora spp. has been carried out by CALMs Science Division. Three plants were tested and were found to be resistant to the disease.

There has been some debate by field staff as to the differences between Conospermum densiflorum subsp. unicephalatum and the common subsp. densiflorum. Populations of the two subspecies occur in the same area in identical habitat, and some specimens have been shown to have properties from both subspecies in the flower heads of the same plant. As the distinction between the two subspecies is largely based on floral characteristics, genetic studies are therefore required to ascertain the relationship between the two taxa.

Threats

Conospermum densiflorum subsp. unicephalatum was declared as Rare Flora on 28 November 1997 under the Western Australian Wildlife Conservation Act 1950. It currently meets World Conservation Union (IUCN 2000) Red List category Endangered (EN) under criteria B1ab(iii)+B2ab(iii) as it is only known from five populations totalling 295 mature plants growing over a narrow geographic range with some decline in the quality of the habitat. The taxon is also listed as Endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The main threats are habitat fragmentation, road and rail maintenance, weed invasion, inappropriate fire regimes, and lack of associated vegetation.

  • Habitat Fragmentation is a serious threat to the long term survival of this subspecies as it occurs over such a small range (10km) and exists in narrow strips of remnant vegetation in a disturbed environment.
  • Road and rail maintenance activities threaten all populations. Threats include grading, chemical spraying, construction of drainage channels and the mowing of roadside vegetation. Several of these actions also encourage weed invasion. Westnet Rail is currently replacing many of the jarrah railway sleepers with concrete sleepers on the GinginMoora stretch of rail line, and this has the potential to impact populations.
  • Weed invasion is a major threat to all populations. 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 easy ignition of high fuel loads, which are produced annually by many weed species.
  • Inappropriate fire regimes would affect the viability of the populations, as Conospermum densiflorum subsp. unicephalatum appears to be an obligate seeder that germinates following fire or other disturbance. The soil seed bank is therefore likely to be rapidly depleted if fires recur 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.
  • Lack of associated vegetation is a threat to all road reserve populations. As a result, pollinators and any native digging and burrowing animals that may historically have disturbed the soil and thereby stimulated germination, are likely to be infrequent or absent. In addition, with little vegetation present providing a buffer, weeds (in particular grasses) are able to invade from the road.
  • Fertiliser and herbicide drift from adjacent farmlands also pose potential threats to many of the Conospermum densiflorum subsp. unicephalatum populations.

Summary of population information and threats

Pop. No. & Location Land Status Year/No. plants Condition Threats
1A Bindoon-Moora Road, North of Gillingarra MRWA Road Reserve 1996 300+*
1999 50+
2000 150+*
2003 251 (532)
Moderate Road and rail maintenance activities, weed competition, inappropriate fire regimes
1b Bindoon-Moora Road, North of Gillingarra Westnet Rail Rail Reserve 1996 300+*
2000 150+*
2003 0
Moderate Road and rail maintenance activities, weed competition, inappropriate fire regimes
2A. Bindoon-Moora Road, South of Gillingarra MRWA Road Reserve 1996 250*
1999 250+ *
2003 1
Moderate Road and rail maintenance activities, weed competition, inappropriate fire regimes
2B. Bindoon-Moora Road, South of Gillingarra Westnet Rail Rail Reserve 1996 250*
1999 250+ *
2003 31(185)
Moderate Road and rail maintenance activities, weed competition, inappropriate fire regimes
3 Bindoon-Moora Road, South of Gillingarra Westnet Rail Rail Reserve 2003 1 Moderate Road and rail maintenance activities, weed competition, inappropriate fire regimes, population size
4 Bindoon - Moora Road, North of Gillingarra Westnet Rail Rail Reserve 2000 10+
2000 60+
2003 11 (169)
Moderate Road and rail maintenance activities, weed competition, inappropriate fire regimes
5 Bindoon - Moora Road. North of Gillingarra Westnet Rail Rail Reserve 2003 1 Moderate Road and rail maintenance activities, weed competition, inappropriate fire regimes, population size.

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 populations or within the defined critical habitat of Conospermum densiflorum subsp. unicephalatum 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.

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 Conospermum densiflorum subsp. unicephalatum comprises:

  • the area of occupancy of known populations;
  • areas of similar habitat within 200 metres of known populations, ie. gravel or clay soils that support heathland consisting of Dryandra spp., and Allocasuarina campestris (these provide potential habitat for natural range extension);
  • remnant vegetation that surrounds or links several populations (this is necessary to allow pollinators to move between populations); and
  • 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).

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

Given that this taxon is listed as endangered it is considered that all known habitat is habitat critical. In addition, all populations, including those resulting from translocation, 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.

Benefits to other species/ecological communities

Recovery actions implemented to improve the quality or security of the habitat of Conospermum densiflorum subsp. unicephalatum will also improve the status of Calothamnus pachystachyus (Priority 4) and may benefit populations of Dryandra serratulioides subsp. serratulioides that occur in the habitat.

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 Australias responsibilities under that Convention. However, as Conospermum densiflorum subsp. unicephalatum is not listed under any specific 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 and, according to the Department of Indigenous Affairs Aboriginal Heritage Sites Register, no registered sites are known from the habitat of the species. Input and involvement will be sought from any indigenous groups that have an active interest in the areas that are habitat for Conospermum densiflorum subsp. unicephalatum, and this is discussed in the recovery actions.

Social and economic impacts

As the known populations are on road and rail reserves, the implementation of this recovery plan is unlikely to cause significant adverse social and economic impacts.

Evaluation of the Plans Performance

CALM, in conjunction with the Moora District Threatened Flora Recovery Team will evaluate the success of this Interim Recovery Plan. In addition to annual reporting on progress and evaluation against the criteria for success and failure, the plan will be reviewed within five years of its implementation. Any changes to management or recovery actions will be documented accordingly.