Wongan Hills Triggerplant (Stylidium coroniforme) Interim Recovery Plan 2003-2008

Interim recovery plan no. 149
Gillian Stack, Nicole Willers and Andrew Brown
Department of Conservation and Land Management, WA, 2003

1. Background

History

Stylidium coroniforme was first collected from the Wongan Hills area in 1964 by M. Rogers. By 1980 the single known population had declined to one plant. Fortunately more populations were later found in the same general area and in 1989 a further two populations were found near Maya some 100 km north of the Wongan Hills. Recent molecular evidence suggests that these may represent a different species (Coates, pers. comm.). A three year Recovery Plan was written for the species in 1995 (Stace and Coates, 1995) with major recovery actions undertaken including, propagation of the species, rehabilitation of a gravel pit in which it occurs and progress towards changing the care, control and management of a Water Reserve that supports several populations. Some seed has been collected and stored at the Threatened Flora Seed Centre (TFSC) and a small living collection exists at the Botanic Garden and Parks Authority (BGPA).

Since 1998, five new populations have been discovered, one of them (Population 6a to 6e) on a Nature Reserve. While Population 1 appears to be relatively stable, Populations 2 to 5 are in decline. Populations 6 to 10 have insufficient historical data to ascertain population expansion or decline.

Stylidium coroniforme is a short-lived species that appears following disturbance events such as fire and light grading with a decline in plant numbers several years post disturbance (Brown et al. 1998).

Description

Stylidium coroniforme is a small, perennial, stocky, closely branching plant, with several loose rosettes of linear greyish-green leaves. Leaves are 3-4 cm long, becoming wider in the upper third and ending in a white point at the apex. Under favorable conditions a flowering stem, 10 to 15 cm tall, arises from each rosette. Each stem holds a number of short-stalked flowers in a pyramidal raceme up to 12 cm long. The corolla is creamy pink with red spots at the throat and dark red lines on the outer surface of the petals (Erickson and Willis, 1966; Brown et al. 1998).

Stylidium coroniforme is closely related to short fruited S. limbatum as they share the same long ovary, racemose scape and marginate leaves. The corolla resembles that of S. dichotomum, which has a bare throat and cushion-like stigma. The name of the species is in reference to the attractively crown-like arrangement of inflorescences, encircling each cluster of rosettes (Erickson and Willis, 1966).

Distribution and habitat

Stylidium coroniforme is currently known from two disjunct areas. The main area of distribution is in Wongan Hills while the other is near Maya about 140 km to the north. Recent genetic analysis suggests that plants in the two areas represent different taxa and it is likely that the taxon represented in the Maya populations will be described as distinct (Coats pers. comm.). If this happens, the Maya taxon will be proposed as Declared Rare Flora in its own right and the ranking of Stylidium coroniforme will neeed to be reviewed. Stylidium coroniforme grows on shallow yellow sand over laterite on open areas in low scrub and heath (Brown et al. 1998).

There are ten populations currently known. The two populations near Maya occur on road and rail reserves. Of the six populations known from the Wongan Hills, four occur on a Water Reserve, two on private property, one on a Nature Reserve and one on an Experimental Farm Reserve.

Biology and ecology

Seed of Stylidium coroniforme germinates after habitat disturbance with young plants recorded following fire, roadworks and gravel extraction and the slashing of associated vegetation during power line maintenance. Following germination, plants mature and set seed quickly, with individual plants living between 5 and 15 years. Seed then persists in the soil for a number of years awaiting another disturbance event.

Bombyllid and syrphid flies and a range of native bees have been reported to be pollen vectors for the species. They are attracted by colourful petals. Nectar guides are present and there is a copious nectar flow at the throat of the flower (Stace & Coates, 1995).

Staff from the Botanical Garden and Parks Authority (BGPA) have successfully propagated this species using division and cuttings (personal communication A. Shade ¹). The species has also been successfully cultured from leaf tissue, resulting in minimal disturbance to wild plants. The minute seeds germinate readily on a moist medium in autumn (Stace & Coates, 1995).

The details above refer to the Wongan Hills populations of Stylidium coroniforme. The new taxon represented by the recently discovered Maya populations will require research to clarify its biological and ecological needs and relevant recovery actions.

Threats

Stylidium coroniforme was declared as Rare Flora in April 1980. It currently meets World Conservation Union (IUCN, 2000) Red List Category 'EN' under criteria B2ab(iii,v) due to the area of occupancy estimated to be less than 500 km2, the severe fragmentation of populations and the continuing decline in the area, extent and quality of habitat and the number of mature individuals. The main threats are poor recruitment, lack of and degraded habitat, accidental destruction and fire.

  • Inappropriate fire regimes may affect the viability of populations. It is thought that the species germinates from soil-stored seed following fire but frequent fire may kill plants before they reach maturity and replenish the seed bank. Until the ideal fire frequency for optimal response of Stylidium coroniforme has been determined, fire should, as much as possible, be prevented from occurring in the area of populations.
  • Trampling by stock is a threat to Populations 1 and 9 where fences are in poor repair. In addition to direct physical damage, the presence of stock will degrade habitat through grazing and trampling of associated vegetation, erosion and the introduction of weeds. Any reduction of plant diversity through stock damage may result in the reduction of pollinators.
  • Salinisation is threatening Population 9 where nearby vegetation is showing the impact of rising saline water tables. The effects of this on Stylidium coroniforme is unknown but will almost certainly be detrimental.
  • Maintenance activities such as track, powerline and water pipe maintenance threaten Populations 2, 3, 4 and 5. Threats include grading, chemical spraying and earth movement. These activities are likely to cause direct damage to existing plants and encourage weed invasion but may also have the positive effect of stimulating germination of soil-stored seed.
  • Poor recruitment currently affects Populations 2, 5 and 7.
  • Weed competition threatens Population 9, mainly along the existing firebreak which is the northern boundary of the population. Weeds suppress plant growth by competing for light, soil moisture, nutrients and pollinators. 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 grass weed species.
  • Grazing by kangaroos and rabbits is resulting in direct plant loss and the introduction and encouragement of weeds through droppings and warren construction. Rabbits and kangaroos are selectively grazing young plants, thus impacting on recruitment.
  • Track use threatens Populations 2 and 5 both through direct physical contact and habitat modification (soil compaction and erosion).
  • Off-track vehicle use threatens Population 2. Trail bikes are used recreationally in the area and have the potential for direct physical contact, soil compaction and erosion.
  • Mining for gravel or sand is a potential threat to populations 2 and 7. If mining were to commence it would damage or destroy existing plants.
Summary of population information and threats
Pop. No. & Location Land Status Year/No. plants Condition Threats
1. Rogers Private Property 1994 28 (1) [2]
1995 23 (1) [5]
2001 25 (1) [11]
Moderate Grazing by stock, road maintenance, inappropriate fire, poor recruitment
2. Wongan Hills Water Reserve 1994 123 (4)
1995 37
2000 5 [5]
Poor Track use and maintenance, mining for gravel or sand, off-track vehicle use, inappropriate fire, poor recruitment
3a. Maya Main Road Reserve 1994 18 [1]*
1995 14 [2]*
2000 6 (3) [several]*
2001 6*
Poor Road maintenance, inappropriate fire, poor recruitment
3b. Maya Railway Reserve 1994 *
2000 *
2001 *
Poor Rail maintenance, inappropriate fire, poor recruitment
4a. Maya Main Road Reserve 1994 105 [11]*
1995 75 (10) [29]*
2000 47*
2001 48*
Moderate Road maintenance, inappropriate fire, poor recruitment
4b. Maya Railway Reserve 1994 *
1995 *
2000 *
2001 *
Moderate Road and rail maintenance, inappropriate fire, poor recruitment
5. Wongan Hills Water Reserve 1994 151
1995 108
2000 46 [3]
2002 20 [29]
Poor Track use and maintenance, powerline maintenance, inappropriate fire, poor recruitment
6a. Elphin Nature Reserve 1999 65
2001 204 [2]
Healthy Firebreak/track maintenance, inappropriate fire
6b Elphin Nature Reserve 2000 1 Healthy Inappropriate fire, poor recruitment
6c. Elphin Nature Reserve 2000 1 Healthy Inappropriate fire, poor recruitment
6d. Elphin Nature Reserve 2000 70 Healthy Inappropriate fire, poor recruitment
6e. Elphin Nature Reserve 2000 6 (1) Healthy Inappropriate fire, poor recruitment
7. Wongan Hills Water Reserve 2000 1
2001 2
Healthy Mining for gravel, inappropriate fire, poor recruitment
8a. Wongan Hills Water Reserve 2000 1 Healthy Inappropriate fire
8b. Wongan Hills Water Reserve 2001 1700 Healthy Inappropriate fire, water runoff
9. Wongan Hills Experimental Farm Reserve 2001 800 Healthy Grazing by stock and other fauna, salinisation, weed competition, inappropriate fire
10. Elphin Private Property 2001 50 Healthy Inappropriate fire

Number in ( ) = number of juveniles. Number in [ ] = number of dead plants. * = total for all subpopulations combined.

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 (EPBC Act)).

The critical habitat for Stylidium coroniforme comprises:

  • the area of occupancy of known populations;
  • areas of similar habitat within 200 metres of known populations, i.e. shallow yellow sand over laterite on open areas in low scrub and heath (these provide potential habitat for natural range extension);
  • corridors of remnant vegetation that link populations (these are necessary to allow pollinators to move between populations and are usually road and rail verges);
  • additional occurrences of similar habitat that do not currently contain the species 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 species is listed as Endangered it is considered that all habitat is important to the survival of the species and that all populations are important.

Benefits to other species/ecological communities

Recovery actions implemented to improve the quality or security of the habitat of Stylidium coroniforme populations will improve the status of remnant vegetation in which 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 Stylidium coroniforme 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.

Social and economic impacts

The implementation of this recovery plan is unlikely to cause significant adverse social and economic impacts. Just two of the 10 known populations are on Private property and may cause some minor impact on farming activities.

Evaluation of the Plan's Performance

The Department of Conservation and Land Management in conjunction with the Wongan/Ballidu Threatened Flora 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.

Guide for decision-makers

Section 1 provides details of current and possible future threats. Developments or on-ground works in the immediate vicinity of the population or within the defined critical habitat of Stylidium coroniforme require assessment. No developments should be approved unless the proponents can demonstrate that they will not have a significant impact on the species, its habitat or potential habitat or the local surface and ground water hydrology such that drainage in the habitat of the species would be altered