Irenepharsus trypherus (Illawarra Irene) Recovery Plan

NSW Department of Environment and Conservation, 2005
ISBN: 1 7412 2145 5

5 Distribution and Habitat

5.1 Definitions

5.1.1 Populations

Populations are defined by the International Union for the Conservation of Nature and Natural Resources (IUCN 1994) as “geographically or otherwise distinct groups between which there is little [genetic] exchange, typically less than one migration per year”. A migration in the case of plant species is considered to be the movement of seed propagules or pollen between populations.

Where there is inadequate information on a species with which to assess the extent to which genetic material is exchanged (as is the case for I. trypherus), a population can be defined using the 'rule of thumb' given by Keith et al. (1997) as a 'geographic discontinuity of more than 1 km'.

Consequently, in this recovery plan, discrete groups of I. trypherus plants which are not separated from other discrete groups by more than one kilometre are considered to be a single population. Following this definition, ten populations of I. trypherus can be identified from historical records (see Section 6.3.2).

5.1.2 Sites and sub-sites

For this recovery plan, sites are defined as discrete groups of I. trypherus plants that are separated from other groups by an arbitrary distance of 200 metres or more. These sites have been labelled with the prefix Ir, followed by a unique number for each site (eg Ir1, Ir2, etc). Sites may also be termed populations if the distance to the nearest site is greater that one kilometre (see definition above).

Sites have been further divided into sub-sites (Ir11a, Ir11b etc) where discrete groups of plants at a site are separated from other groups of plants at that site by an arbitrary distance of 50 metres or more.

A total of 17 sites comprising 25 sub-sites have been recorded for I. trypherus.

5.2 Distribution

I. trypherus is a NSW endemic that is recorded from 17 sites within Kiama, Shellharbour, Shoalhaven, Wingecarribee and Wollongong local government areas (LGAs). These sites are located within the Sydney Basin Bioregion, as defined in the Interim Biogeographic Regionalisation of Australia (Thackway & Cresswell 1995).

The main distributional range of I. trypherus extends from Marshall Mount (Wollongong LGA) to Lake Yarrunga in Morton National Park (Wingecarribee LGA). Sites within this range of approximately 41 kilometres are largely confined to the upper slopes of the ridge systems that extend south and east from the Illawarra escarpment (ie Stockyard Mountain, Marshall Mount, Johnstons Ridge and Hindmarsh Ridge). One site has been recorded outside this range at Ettrema Gorge (Ir13) in Morton National Park, approximately 29 kilometres south of Lake Yarrunga.

An Atlas of NSW Wildlife record from 1861 for an I. trypherus site in the Shoalhaven region has not been considered in this recovery plan, as the record is only accurate to 100 km.

Atlas of NSW Wildlife record from 1861 for an I. trypherus site in the Shoalhaven region

5.3 Land tenure and zoning

Table 1 describes the tenure, zoning and status of the 17 recorded I. trypherus sites.

5.3.1 Conservation reserves

Six of the seven I. trypherus sites that have been recorded from conservation reserves were surveyed during the preparation of this plan. I. trypherus plants were confirmed to occur at four of these sites.

Budderoo National Park (Minnamurra Rainforest)

Two of three sites that have been recorded within the Minnamurra Rainforest section of Budderoo NP were confirmed. A total of 137 I. trypherus plants were observed at Ir11 between December 2003 and May 2004, while two mature plants were observed at Ir10 in February 2002. A subsequent survey of Ir10 in December 2003 failed to locate any I. trypherus plants.

No I. trypherus plants were located at the site of a 1959 record for a third location within Minnamurra Rainforest (Ir14). The spatial accuracy of this record is questionable however, as it describes the location as a rocky cliff face in gorge near falls. The site lies more than 1.5 kilometres from the lower and upper falls and it is possible that the record actually relates to site Ir10.

Budderoo National Park (Kangaroo Valley)

A total of 332 plants were observed within (or immediately adjacent to) the Kangaroo Valley section of Budderoo NP (Ir12) in February 2002. A small proportion of this site extends onto an adjacent freehold property.

Macquarie Pass National Park

A total of 480 plants were observed in Macquarie Pass NP (Ir2) in January 2004 (M. Robinson pers. comm.). One I. trypherus plant had previously been recorded from this site in 1993. Surveys in 1998, 2001 and 2002 failed to locate any I. trypherus plants in the vicinity of the 1993 record and the species was presumed to be extinct at this location. The plants observed in 2004 are in the same location as the 1993 record and have presumably regenerated from the soil seed bank.

Morton National Park

I. trypherus was recorded from Ettrema Gorge (Ir13) in 1984 although the number of plants present was not noted. Targeted survey in the vicinity of the original sighting failed to locate the species in 2002.

A second site within Morton NP, an unnamed creek above Lake Yarrunga (Ir16), was discovered in the 1990s although the number of plants present was not recorded (A. Bofeldt, Wollongong Botanic Gardens, pers. comm.).

5.3.2 Freehold Land

Attempts were made during the preparation of this plan, to determine the present status of the eight I. trypherus sites that have been recorded on freehold land since 1960. The following results were achieved:

  • I. trypherus plants were confirmed to occur at three Stockyard Mountain sites (Ir5, Ir7 and Ir9);
  • Access to a further three Stockyard Mountain sites (Ir4, Ir6 and Ir8) was denied by landholders; and
  • No I. trypherus plants were located at the North Marshall Mount (Ir1) or Johnstons Ridge (Ir3) sites.
Table 1: Location, tenure, zoning and status of I. trypherus sites
Site Location LGA Tenure Zoning* Last Seen Status
IR1 Nth Marshall Mt Wollongong Freehold 7(b) 1999 Not located
IR2 Macquarie Pass NP Shellharbour DEC 8(a) 2004 Confirmed
IR3 Johnstons Ridge Shellharbour Freehold 7(e) 1990s Not located
IR4 Stockyard Mountain Shellharbour Freehold 1(a) 1992 Not surveyed
IR5 Stockyard Mountain Shellharbour Freehold 1(a) 2002 Confirmed
IR6 Stockyard Mountain Shellharbour Freehold 1(a) 1993 Not surveyed
IR7 Stockyard Mountain Shellharbour Freehold 1(a) 2002 Confirmed
IR8 Stockyard Mountain Shellharbour Freehold 1(a) 1993 Not surveyed
IR9 Stockyard Mountain Shellharbour Freehold 1(a) 2001 Confirmed
IR10 Minnamurra Rainforest (north) Kiama DEC 8(a) 2002 Confirmed
IR11 Minnamurra Rainforest (south) Kiama DEC 8(a) 2002 Confirmed
IR12 Kangaroo Valley Shoalhaven DEC/Freehold 8(a)/7(e) 2002 Confirmed
IR13 Ettrema Gorge Shoalhaven DEC 8(a) 1984 Not located
IR14 Minnamurra Falls Kiama DEC 8(a) 1955 Not located
IR15 Upper Kangaroo River Shoalhaven Freehold 1(a) 1943 Not surveyed
IR16 Lake Yarrunga Wingecarribee DEC 8(a) 1990s Not surveyed
IR17 Barrengarry Shoalhaven Freehold 1(a) 1948 Not surveyed

*1 = Rural uses, 7 = Environmental protection, 8 = National Park

Wollongong LGA

A site at Marshall Mount (Ir1) occurs on freehold land that is zoned 7(b) Environmental Protection (Conservation) under Wollongong LEP 1990. The remnant vegetation of this property is the subject of a Property Agreement under the Native Vegetation Conservation Act 1997. The species was last observed at the site in 1999 when 35 plants were present. Targeted survey failed to locate any I. trypherus plants in 2001 and 2002.

Shellharbour LGA

Six sites occur on three freehold properties at Stockyard Mountain (Ir4 to Ir9). Cattle grazing is the primary land-use on these properties, which are zoned 1(a) Rural under Shellharbour LEP 2000. The species was observed at each of the three sites that the DEC was permitted access to during the preparation of this plan. A total of 16, 44 and 84 I. trypherus plants were recorded at sites Ir5, Ir7 and Ir9 respectively.

A site at Johnstons Ridge (Ir3) occurs on freehold land that is zoned 7(e) Environmental Protection (Escarpment) under Shellharbour LEP 2000. The species was first discovered at this site in the early 1990s although the number of plants present was not recorded. Targeted survey failed to locate the species here in 1998 or 2002.

Shoalhaven LGA

A small number of plants from the Kangaroo Valley site (Ir13) extend onto adjacent freehold property that is zoned 7(e) Environmental Protection (Escarpment) under Shoalhaven LEP 1985. The plants in question occur on a cliff edge immediately upslope of the main site, which lies within Morton NP.

Two records from the 1940s occur on freehold land zoned 1(a) Rural under Shoalhaven LEP 1985. The spatial accuracy of these records is questionable however, given that the records are for floodplain areas which is unusual habitat for the species (see Section 5.4.1). Consequently, these sites were not surveyed during the preparation of this plan.

5.4 Habitat

5.4.1 Landform

I. trypherus typically occupies the upper slopes of the ridge systems that extend south and east from the Illawarra escarpment (ie Stockyard Mountain, Marshall Mount, Johnstons Ridge and Hindmarsh Ridge). The species has also been recorded from the deep gorges of the Shoalhaven River and its tributaries.

Two I. trypherus records from the 1940s are for sites that are located on the floodplain of the upper Kangaroo River. As mentioned previously, this is unusual habitat for the species and it is suspected that these records actually refer to sites that are located on the nearby escarpment slopes.

The sites that were surveyed during the preparation of this plan generally occupied steep rocky near cliff lines and ridge tops. These sites were frequently located on unstable slopes that are susceptible to small-scale erosion events. Sites were less typically located on the narrow benches of cliff lines with occasional plants observed growing in the crevices of sheer cliff faces.

5.4.2 Geology and soils

I. trypherus has been recorded growing on the following substrates (see Table 2):

  • Minnamurra Latite;
  • Cambewarra Latite;
  • Illawarra Coal Measures;
  • Budgong Sandstone;
  • Silurian Sandstone; and
  • Conjola conglomerate.

I. trypherus sites frequently occur near the boundary of two substrates, particularly where bands of latite outcrop between Budgong Sandstone and/or Illawarra Coal Measures. It is likely that differences in the erosion resistance of these substrates create the habitat conditions (ie steep rocky slopes and cliff lines) that are favoured by the species.

Associated soils are usually brown loams with a characteristically high percentage (generally between 30 and 60 per cent surface cover) of unconsolidated and/or outcropping rock material. I. trypherus plants have also been observed growing in small accumulations of organic matter in the cracks of rock outcrops and cliff faces.

5.4.3 Altitude

The altitudinal range of I. trypherus is 85 to 400 metres with the vast majority of sites located between 150 and 340 metres (see Table 2).

5.4.4 Climate

The Illawarra area (where the core distribution of I. trypherus occurs) has a generally mild climate with extremes in temperature being moderated by coastal effects (Mills & Jakeman 1995). Average minimum and maximum temperatures are closely related to altitude and proximity to the coast (see Table 3).

Rainfall is very high compared with much of NSW. Average annual rainfall figures range from just below 1000 mm near Lake Illawarra to over 1800 mm at Barren Grounds with the higher rainfall isohyets closely correlated to the top of the escarpment (Mills & Jakeman 1995).

Table 2: Physical characteristics at I. trypherus sites
Site* Altitude
(m)
Geology** Slope
IR1 160 Minnamurra Latite -
IR2 160 Budgong Sandstone 41
IR3 190 Budgong Sandstone -
IR4 290 Cambewarra Latite  
IR5 240 Budgong Sandstone 41
IR6a 230 Cambewarra Latite -
IR6b 225 Cambewarra Latite -
IR7 280 Budgong Sandstone 37
IR8 150 Cambewarra Latite -
IR9 250 Cambewarra Latite -
IR10 265 Cambewarra Latite -
IR11a 290 Illawarra Coal Measures 38
IR11b 300 Illawarra Coal Measures 38
IR11c 310 Illawarra Coal Measures 36
IR11d 280 Illawarra Coal Measures 42
IR11e 260 Cambewarra Latite 42
IR12a 310 Budgong Sandstone 38
IR12b 340 Budgong Sandstone 32
IR12c 340 Budgong Sandstone 45
IR12d 400 Budgong Sandstone 35
IR13 330 Silurian Sandstone -
IR16 85 Conjola Conglomerate -

* Sites Ir14, Ir15, and Ir17 are not included as the spatial accuracy of these records is questionable
**following Bowman (1974a, 1974b and 1974c) or Department of Mines (1966) where geology has not been determined in the field

The distribution of rainfall within the area can also be attributed to winds blowing from the south (Hazelton 1992). One third of the mean annual rainfall for the area occurs in January, February and March with a marked secondary rainfall peak in June (Hazelton 1992).

Westerly airflows dominate the weather during winter producing cooler, drier conditions although few or no frosts occur on the coastal plain (Hazelton 1992). Drought conditions can occur in the area and rainfall data indicates the occurrence of distinct runs of wet or dry years which last between six and eight years (Mills & Jakeman 1995).

Modelling by the DEC indicates that the following climatic conditions occur at I. trypherus locations in the Illawarra area:

  • Mean annual temperature of between 14.6 and 16.1°C;
  • Mean maximum temperature of between 24.5 and 25.7C during the warmest period;
  • Mean minimum temperature of between 4.3 and 6C during the coldest period;
  • Mean annual precipitation of between 1389 and 1813 mm.

This modelling also indicates that the I. trypherus sites that lie outside the Illawarra area (at Ettrema Gorge and Lake Yarrunga) experience a more extreme range of temperatures (from 3.4°C during the coldest period to 27.3°C during the warmest period) and a significantly lower annual precipitation (898 mm and 948 mm) than the other sites.

5.4.5 Associated Vegetation

The vegetation associations present at I. trypherus sub-sites can be categorised into the following broad categories:

  • Moist sclerophyll open forest and woodland;
  • Sclerophyll grassy open forest;
  • Backhousia myrtifolia low open to closed forest;
  • Subtropical rainforest; and
  • Mixed subtropical - warm temperate rainforest.

Table 4 shows the distribution of sub-sites across these categories. The categories are described below with more detailed vegetation descriptions for the sub-sites surveyed during the preparation of this plan provided in Appendix 4.

Moist sclerophyll open forest and woodland

Seven sub-sites occupy moist sclerophyll open forest or woodland vegetation. These sub-sites are located on the lower escarpment slopes and foothills at the transition between the grassy sclerophyll forests of the exposed ridges and slopes, and the subtropical rainforest of adjacent sheltered gullies.

A variety of canopy species have been recorded at these sub-sites however a characteristic low mesic shrub layer of dry subtropical rainforest aligned species is always present.

Table 3: Average temperatures (°C) for Moss Vale and Wollongong climatic stations
Station Altitude Distance inland Average
Jan max.
Average
July min.
Average
annual max.
Average
annual min.
Moss Vale 672 m 45 km 21.6 1.2 19.4 6.8

Wollongong 12 m 0.5 km 25.9 7.8 21.6 12.6

Source: Mills & Jakeman (1995)

Vegetation associations present within the group include:

  • Eucalyptus tereticornis (Forest Red Gum) - E. quadrangulata (White Box) moist open forest to woodland;
  • E. quadrangulata - E. muelleriana (Yellow Stringybark) moist open forest;
  • E. tereticornis - E. eugenioides (Thin-leaved Stringybark) moist woodland; and
  • E. quadrangulata - E. fastigata (Brown Barrel) moist open forest.

The mid-storey at these sub-sites ranges in height from two to ten metres with a projected cover of between 20 and 60 per cent. Commonly recorded shrub species include Acacia binervata, Acacia maidenii, Cassine australis, Clerodendrum tomentosum, Claoxylon australe, Diospyros australis, Exocarpus cupressiformis, Notelaea venosa, Breynia oblongifolia and Rapanea variabilis.

Groundcovers occupy less than 30 per cent projected cover (although 60 per cent cover was recorded at one sub-site) and include Adiantum aethiopicum, Asplenium flabellifolium, Doodia sp., Plectranthus parviflorus, Dianella revoluta and Sigesbeckia orientalis. Grasses including Poa spp., Danthonia spp., Oplismenus sp., Themeda australis, and Stipa sp. are present in the more open areas. Climbers include Eustrephus latifolius, Geitnoplesium cymosum, Pandorea pandorana, Kennedia sp., Marsdenia sp. and Cayratia clematidea.

Sclerophyll grassy open forest

One sub-site in the upper Kangaroo River valley (Ir12c) is located in a relatively undisturbed sclerophyll open forest with a sparse mid-storey and an open grassy understorey. The canopy at this sub-site is 18 to 26 metres tall with 30 per cent projected cover, and consist of Eucalyptus piperita (Sydney Peppermint) and Eucalyptus saligna X botryoides.

A sparse shrub layer (Acacia maidenii, Macrozamia communis, Synoum glandulosum, Hymenanthera dentata, Pomaderris aspera and Indigofera australis.

A dense groundcover (80 per cent projected cover) of Poa labillardieri, Craspedia sp., Adiantum formosum, Plectranthus parviflorus, Pellaea falcata, Sigesbeckia orientalis and Rubus sp. is also present. Climbers include Stephania japonica var. discolor and Eustrephus latifolius.

Two sites (Ir6 and Ir8) are located in an area that is mapped as containing Eucalyptus pilularis (Blackbutt) Tall Forest in Mills (2000). The Atlas of NSW Wildlife descriptions of these sites do not correspond with this vegetation type and it is likely that the sites actually contain either E. tereticornis - E. quadrangulata moist open forest or E. quadrangulata - E. muelleriana moist open forest.

Backhousia myrtifolia low open to closed forest

Eight sub-sites occupy a low closed or open forest dominated by Backhousia myrtifolia (Ironwood). The canopy height is four to ten metres with 70 to 90 per cent projected cover at all sub-sites except Ir11e, where 30 per cent projected canopy cover was recorded. Emergent eucalypts (E. quadrangulata and E. piperita) were observed at three sub-sites (Ir2, Ir12a, and Ir12b).

Shrub species present include Notelaea venosa, Streblus brunonianus, Breynia oblongifolia, Clerodendrum tomentosum, Rapanea variabilis, Bursaria spinosa and Acacia maidenii. The density of groundcovers is highly variable (10 to 90 per cent projected cover) consisting of Oplismenus sp., Poa labillardieri, Microlaena stipoides, Adiantum spp., Asplenium flabellifolium, Plectranthus parviflorus, Gonocarpus sp. and climbers including Glycine sp. and Aphanopetalum resinosum.

Table 4: Vegetation associations at I. trypherus sub-sites by LGA
Vegetation Association Sub-site LGA
E. tereticornis (Forest Red Gum) - E. quadrangulata (White Box) moist open forest to woodland 5 Shellharbour
11d Kiama
E. quadrangulata - E. muelleriana (Yellow Stringybark) moist open forest 7, 9 Shellharbour
E. tereticornis - E. eugenioides (Thin-leaved Stringybark) moist open forest 11a, 11b Kiama
E. quadrangulata - E. fastigata (Brown Barrel) moist woodland 11c Kiama
E. longifolia moist open forest 6 Shellharbour
E. piperita (Sydney Peppermint) - E. saligna X botryoides open forest 12c Shoalhaven
Backhousia myrtifolia low open to closed forest 1, 2 Wollongong
3, Shellharbour
11e, Kiama
12a, 12b, 12d, 13 Shoalhaven
Subtropical rainforest 4 Shellharbour
Mixed subtropical - warm temperate rainforest 10 Kiama
Subtropical rainforest

A site at Stockyard Mountain (Ir4) is described in the Atlas of NSW Wildlife as occupying a cliff edge exposed to full sun in subtropical rainforest. Associated species are listed as Cassine australis, Nysanthes sp., Plectranthus parviflorus, Aphanopetalum resinosum and Delairea odorata.

Mixed subtropical - warm temperate rainforest

A site in Minnamurra Rainforest (IR10) occurs in closed forest vegetation that is consistent with the mixed subtropical/warm temperate rainforest type of Mills & Jakeman (1995). The canopy at this site is 25 metres tall with 80 per cent projected cover. Associated species include Dendrocnide excelsa, Doryphora sassafras, Diospyros australis, Baloghia inophylla and Pennantia cunninghamii.