Round-leafed Honeysuckle (Lambertia orbifolia subsp. Orbifolia ms) 2002-2007

Interim Recovery Plan No. 115
Robyn Phillimore and Andrew Brown
Department of Conservation and Land Management, WA, 2003

1. Background

History

C.A. Gardner described Lambertia orbifolia in 1964 from a collection made from the Narrikup area by K.R. Newbey in the same year. The specific name, derived from the Latin orbis, refers to the rounded leaves. The species was subsequently also found in the Scott River area some 200 km to the south-west. Due to this disjunction it was thought that plants from the two areas may represent two subspecies. In 1999 research was conducted and, based on differences found in the genetic structure between plants in the two areas (Byrne et al., 1999; Coates & Hamley, 1999), L. orbifolia was split into two subspecies. These being L. orbifolia subsp. orbifolia ms and L. orbifolia subsp. Scott River Plains (L.W. Sage 684).

Surveys undertaken by Departmental staff and volunteers have resulted in the discovery of two new populations. Currently, Lambertia orbifolia subsp. orbifolia ms is known from three populations (plus a fourth translocated population) containing a total of around 438 plants. Some populations are in decline from fungal pathogens, primarily dieback (Phytophthora cinnamomi).

Description

Lambertia orbifolia subsp. orbifolia ms is an erect shrub or small tree, up to four metres high with distinctive leaves that are held in opposite pairs or in whorls of three. The leaves, which are more or less circular or broadly elliptic, are 1.2 to five centimeters long and wide. Heads of four red flowers, each about five to six centimetres long, are surrounded by a whorl of overlapping bracts. Flowering occurs throughout the year, but is mainly between November and May (Brown et al., 1998).

Lambertia orbifolia subsp. orbifolia ms can be distinguished from L. orbifolia subsp. Scott River Plains (L.W. Sage 684) by its inflorescence, which has a shorter, thinner bract (personal communication G. Keighery ¹). L. orbifolia subsp. orbifolia ms is closely related to L. inermis but differs in its larger, hairier perianth, narrower, truncate bracts and much broader sessile leaves (Gardner, 1964).

¹ Greg Keighery, Principal Research Scientist, Science Division

Distribution and habitat

Lambertia orbifolia subsp. orbifolia ms is endemic to Western Australia where it is found in the Narrikup area. Habitat is Jarrah (Eucalyptus marginata), Marri (Corymbia calophylla) and Banksia woodland on grey/brown/white gravelly, sandy, loam over ironstone. Associated species include Eucalyptus marginata, Corymbia calophylla, Banksia grandis, Agonis hypericifolia, Nuytsia floribunda, Hakea ferruginea, Agonis parviceps, Anarthria prolifera, Bossiaea ornata, Leucopogon verticillatus, Isopogon formosus, Xanthorrhoea preissii, Hakea varia, Adenanthos obovatus, Eucalyptus staeri and Xanthorrhoea platyphylla.

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 Lambertia orbifolia subsp. orbifolia ms comprises:

  • the area of occupancy of the known populations,
  • areas of similar habitat ie. Jarrah, Marri and Banksia woodland on grey/brown/white gravelly, sandy, loam over ironstone, within 200 metres of known populations (these provide potential habitat for natural recruitment),
  • corridors of remnant vegetation that link populations (these are necessary to allow pollinators to move between populations),
  • additional nearby occurrences of similar habitat ie. Jarrah, Marri and Banksia woodland on grey/brown/white gravelly, sandy, loam over ironstone that do not currently contain the subspecies (these represent possible translocation sites).

Biology and ecology

Lambertia orbifolia has populations in two widely separated areas (Narrikup and Scott River Plains). Research on the genetic structure and mating system of the species has shown that these populations have been isolated for quite some time and that this has led to independent evolution. The two forms should therefore be recognised as distinct subspecies (Byrne et al., 1999; Coates & Hamley, 1999).

Results from an Honours project undertaken by L. Sage 2 has shown that Lambertia orbifolia subsp. orbifolia ms (Narrikup) differs from L. orbifolia subsp. Scott River Plains in aspects of flowering, plant longevity and follicle production. L. orbifolia subsp. orbifolia ms plants also have fewer inflorescences. The subspecies is an obligate re-seeder (non sprouter) and is nonserotinous (seed is continually being dehisced). Large quantities of seed do not appear to be stored within the leaf litter or soil and may be eaten by granivores soon after being dehisced (Sage & Lamont, 1994).

The subspecies is killed by fire which appears to be a stimulus for recruitment from seed (Sage & Lamont, 1994). Recruitment is also known to occur in low numbers in unburnt areas (personal communication S Barrett 3). Its response to soil disturbance and weed invasion is unknown although field observations suggest that weed invasion probably affects recruitment (Obbens & Coates, 1997).

As yet, no testing has been undertaken by Science Division staff in relation to Phytophthora cinnamomi susceptibility (personal communication C. Crane 4). However, field observations suggest that the subspecies is very susceptible to the disease (CALM Vegetation Health Service). Keighery (1992) has also identified the subspecies as being highly susceptible.

Threats

Following the splitting of Lambertia orbifolia into two subspecies in September 1999, the subsp. orbifolia ms was ranked as Critically Endangered (CR). It currently meets World Conservation Union (IUCN, 2000) Red List Category 'CR' under criteria B2ab(ii,iii,v) due to it being known from just three populations and a continuing decline in number of individuals, area and quality of habitat. The main threats are disease, grazing, road and track maintenance, weed invasion and inappropriate fire regimes.

  • Disease is a threat to all populations. Subpopulations 3a and 3b are infected with P. cinnamomi with some deaths occurring. Dieback is also downslope of Subpopulations 2d and 2e. Aerial canker (Cryptodiaporthe sp., Diplodina sp.) has been visually identified at Populations 1 and 2.
  • Grazing. Areas of private property that contain Lambertia orbifolia subsp. orbifolia ms are not currently stocked. However, these populations are potentially at risk from possible future grazing and trampling by stock.
  • Road and firebreak maintenance threatens Population 1 and subpopulations 2a, 2b and 3a. Construction of drainage channels, grading and other road maintenance activities impact on the subspecies in these areas. Mowing of road verge vegetation by Shires to improve visibility can affect plants and/or associated habitat.
  • Weed invasion is a minor threat current to all road reserve 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 the easy ignition of high fuel loads, which are produced annually by many grass weed species (Lynch 1987; Saunders et al. 1987; Taylor 1987).
  • Inappropriate fire may affect the viability of populations. Seed of Lambertia orbifolia subsp. orbifolia ms germinates following fire and the soil seed bank would rapidly be depleted if fires recurred before juvenile plants reached maturity. However, it is likely that occasional fires are needed for recruitment. Further investigation is required and will be addressed in management action 14.
Summary of population information and threats
Pop. No. & Location Land Status Year/No. plants Condition Threats
1. WNW Narrikup Shire Road reserve 1999 95+ (26+) [15+ dead] Moderate Disease, fire, road maintenance, weeds
2a. WNW Narrikup Shire Road reserve 1995 *23 (7) [3 dead]
1999 13
Moderate Disease, fire, road maintenance, weeds
2b. WNW Narrikup Private property 1995 *see 2a
1999 2 [1 dead]
Moderate Disease, firebreak maintenance, fire, grazing, weeds
2c. WNW Narrikup Private property 1995 *see 2a
1999 3
Moderate Disease, fire, grazing, weeds
2a. WNW Narrikup Private property 1999 150+ (300+) [10+ dead] Healthy Disease, fire, grazing, weeds
2b. WNW Narrikup Private property 2000 100+ Healthy Disease, fire, weeds
3a. WNW Narrikup Shire Recreation Reserve 1997 24
2000 50+ (200+)
Healthy Disease (dieback infested), firebreak maintenance, fire, weeds
3b. WNW Narrikup Private property 2000 (5) Healthy Disease (dieback infested), fire, weeds
**4. SW Narrikup Conservation Reserve (Flora & Fauna) 1999 540
2000 577
Healthy  

Note: * total for both subpopulations combined.
Numbers in brackets ( ) = seedlings.
** Population 4 = a translocated population.

Guide for decision-makers

Section 1 provides details of current and possible future threats. Developments in the immediate vicinity of any of the populations or within the defined critical habitat of the subspecies require assessment. Developments should not be approved unless the proponents can demonstrate that they will not have a significant impact on the subspecies, its habitat or potential habitat, or have the potential to spread or amplify dieback caused by the plant pathogen Phytophthora cinnamomi.