Paynes Find Mallee (Eucalyptus crucis subsp. Praecipua) 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

Eucalyptus crucis subsp. praecipua was first collected by Southcott in 1979 as E. crucis. Subspecies lanceolata was distinguished from the type subspecies by Brooker and Hopper (1982). E. crucis subspecies praecipua was also recognised as distinct by Brooker and Hopper (1993), following the results of genetic analysis of Eucalyptus crucis populations by Sampson et al. (1988). The name praecipua is derived from the Latin word for special, alluding to its distinct isozyme constituents. Subspecies praecipua has one allele unique to it, and completely lacks an allele that is either fixed or most common in all other populations examined (both subsp. lanceolata and subsp. crucis) (Sampson et al. 1988).

Only two populations are known, and both occur on a large granite outcrop west of Paynes Find. This area lies within a pastoral lease that supports sheep and numerous feral goats.

Description

Eucalyptus crucis subsp. praecipua is a large erect to spreading mallee (or sometimes single-stemmed tree) to 15 m tall with stems to about 30 cm diameter. It has thick, grey, rough bark on lower stems, and red-brown minni ritchi bark above. Brooker and Kleinig (1990) describe minni ritchi as a bark type in which "the outer rich, red-brown smooth bark splits both longitudinally and horizontally, the free edges rolling back without completely detaching to expose new green bark beneath". Young branchlets are smooth, white and glaucous. Juvenile leaves remain opposite for many nodes, lack a petiole and are more or less round with a conspicuous mucro (fine point at the tip). Intermediate leaves are opposite or nearly so, and are ovate with very small to small petioles. Adult leaves are alternate, on slender petioles, and are lanceolate to narrow-lanceolate tapering to a fine, sometimes curved point, with many minute black oil dots. Inflorescences are cream-yellow, axillary and 7-flowered, with slender petioles and peduncles. Buds are glaucous with an obtusely or acutely conical operculum that is lost early in bud development. Fruit are 8-13 mm long and 14-20 mm in diameter (Brooker and Hopper 1982; Brooker and Hopper 1993; Nicolle 2001).

Eucalyptus crucis subsp. praecipua differs from subspecies lanceolata in the larger adult leaves, buds and fruits (Brooker and Hopper 1993). In addition, a study by Sampson et al. (1988) indicated that the genetic distance between the morphologically similar subsp. lanceolata and subsp. praecipua was much larger than the distance of subsp. lanceolata from the morphologically dissimilar subsp. crucis.

Distribution and habitat

Eucalyptus crucis subsp. praecipua is currently known from a single granite rock west of Paynes Find, which lies within a pastoral lease. A total of 56 plants are known from 2 populations. It is found on red-brown loam to sandy loam over granite in low woodland with open low scrub. Associated species include Allocasuarina campestris, Acacia sp., Grevillea sp. and Dodonaea sp.

Biology and ecology

No juveniles have been observed at any of the subpopulations. A seedling was observed in 2002, but in 2003 it was clear that this was a different species. Recruitment would naturally be very low for this large, long-lived taxon, but is necessary to ensure eventual replacement of existing adult trees.

It is thought probable that adults of this taxon resprout after fire and that fire triggers germination of seed, as is the case for many other eucalypts endemic to granite rocks. This pattern is true of close relative E. crucis subsp. lanceolata (Yates et al. 2003). It is likely that most seed is stored in the canopy and therefore avoids most predation. The trees produce abundant fruit. Fruits collected in 2001 contained numerous seeds, which were found to be 90% viable.

Some eucalypt species are known to produce enzymes that inhibit growth of other plants. It is not known whether Eucalyptus crucis subsp. praecipua produces these enzymes, but if so, it would inhibit germination of seed in the vicinity of an adult until the enzyme was no longer produced. This mechanism reduces fatal germination, where germinants are unable to survive the existing level of competition. Available moisture and/or light may also be factors limiting germination.

Feral goats have had an impact on the habitat in the past. Their numbers have been reduced on the station through mustering, and in 2003 there was a wetter winter than in the previous two years, and this resulted in better feed elsewhere on the station. Reduced grazing pressure was evident in 2003.

Threats

Eucalyptus crucis subsp. praecipua was declared as Rare Flora in July 1989, and is currently ranked as Endangered (EN) under World Conservation Union (IUCN) Red List criterion D (IUCN 2000) as less than 250 mature individuals are known. Eucalyptus crucis subsp. praecipua is also listed as Endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The main threat is grazing by feral goats, with inappropriate fire regimes and lack of recruitment posing a potential threat in the long term.

  • Grazing by feral goats and perhaps sheep threatens both populations. Although these animals dont graze the adult eucalypts, they severely restrict recruitment of juveniles to the populations. They can also impact heavily on the supporting habitat through direct grazing, breaking of branches to bring them within reach, soil compaction and introduction of weed seeds. The impact is currently low due to some destocking and goat mustering undertaken by the pastoral leaseholders, and the availability of good feed elsewhere on the lease after a wetter winter than the previous two years.
  • Inappropriate fire regimes may affect the viability of populations, as Eucalyptus crucis subsp. praecipua almost certainly resprouts following fire. If this is the case, the lignotubers may be depleted if fires recur before they can build up resources again. This taxon is likely to be adapted to require fire or other disturbance for recruitment. However, as it is likely that the taxon has a long lifespan, there is no urgent need for fire, or other disturbance in the short to mid-term (C. Yates Dr Colin Yates, Senior Research Scientist (Ecology), CALMs Science Division, pers. comm.).
  • Lack of recruitment is apparent at all populations as no juvenile plants have been observed. As there is abundant seed, and seed viability has been found to be high, this seems most likely to be due to an absence of germination triggers or possibly poor seedling survival.
  • Inappropriate water catchment design may be a threat if there is any attempt to capture water off this granite rock by diverting the flow of rainfall.

Summary of population information and threats

Pop. No. & Location Land Status Year/No. plants Condition Threats
1a. W of Paynes Find Pastoral lease 1981 13
1991 7
2000 12
2003 12
Healthy Grazing, frequent fire, lack of recruitment
1b. W of Paynes Find Pastoral lease 1981 12
1991 23
2000 23
2003 23
Healthy Grazing, frequent fire, lack of recruitment
1c. W of Paynes Find Pastoral lease 1981 2
1991 4
1992 3
2000 3
2003 3
Healthy Grazing, frequent fire, lack of recruitment
1d. W of Paynes Find Pastoral lease 1981 10
1991 10
2000 10
2003 10
Healthy Grazing, frequent fire, lack of recruitment
2. W of Paynes Find Pastoral lease 1981 8
1991 8
2000 8
2003 8
Healthy Grazing, frequent fire, lack of recruitment

Guide for decision-makers

Section 1 provides details of current and possible future threats. Any on-ground works (clearing, water harvesting works etc) in the immediate vicinity of Eucalyptus crucis subsp. praecipua will require assessment. On-ground works should not be approved unless the proponents can demonstrate that they will not have an impact on the taxon, 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 (EPBC Act)).

Eucalyptus crucis subsp. praecipua is listed as Endangered, and as such it is considered that all known habitat for wild or translocated populations is critical habitat. This includes:

  • the area of occupancy of known populations;
  • areas of similar habitat within 200 metres of known populations, i.e. woodland in pockets of red-brown loam on domed granite (these provide potential habitat for natural range extension);
  • corridors of remnant vegetation that link populations (these are other pockets of vegetation on the rock that are 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).

Benefits to other species or ecological communities

Acacia cerestes and Baeckea sp. Paynes Find are both Priority 1 species that occur in the habitat of Eucalyptus crucis subsp. praecipua. These species seem to be rare but are poorly known, and would need further survey to clarify their conservation status before they could be formally gazetted rare. Recovery actions such as reducing goat numbers in the vicinity of Eucalyptus crucis subsp. praecipua populations will also help to protect the ecological community in which the 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 Australias responsibilities under that convention. The taxon is not listed under any specific international treaty, however, and therefore this IRP does not affect Australias obligations under any other international agreements.

Role and interests of indigenous people

An Aboriginal Corporation holds the pastoral lease over the rock on which Eucalyptus crucis subsp. praecipua occurs. The group is involved in the conservation of these populations and also a proposed Indigenous Protected Area elsewhere on the station. The granite rock on which these populations occur is listed as a ceremonial and mythological site on the Register of Aboriginal Sites maintained by the Department of Indigenous Affairs. Artefacts are also associated with this site. Input and involvement will be sought from any indigenous groups that have an active interest in the areas that are habitat for E. crucis subsp. praecipua, and this is discussed in the recovery actions.

Social and economic impacts

The implementation of this recovery plan has the potential to have some limited social and economic impact as both populations of Eucalyptus crucis subsp. praecipua occur on a pastoral lease. Negotiations between stakeholders will continue with regard to the future management of these populations.

Evaluation of the Plans Performance

CALM will evaluate the performance of this IRP in conjunction with the Geraldton District Threatened Flora Recovery Team. In addition to annual reporting on progress with listed actions and comparison against the criteria for success and failure, the plan is to be reviewed within five years of its implementation.