Grevillea caleyi

Family: Proteaceae

Conservation Status

Endangered species in NSW (TSC Act). Also listed as an endangered species at national level in the Endangered Species Protection Act.

Distribution

Grevillea caleyi occurs in northern Sydney over an area of approximately 6 x 6 km which is centred on Terrey Hills and also includes parts of Duffys Forest, Belrose and Ingleside. Within this distribution some 20 stands of Grevillea caleyi, remnants of former populations, persist (Scott et al. 1995, as updated 2000). Only five of these stands occur within, or partly within, National Parks and Wildlife Service lands: three in Ku-ring-gai Chase National Park and two in the eastern section of Garigal National Park.

Pittwater Population

Grevillea caleyi occurs at Ingleside in the vicinity of the Baha'i Temple. The population here extends into both the Pittwater and Warringah Local Government Areas, with plants growing on privately owned land, land owned by the Roads and Traffic Authority and the Department of Land and Water Conservation, as well as in Garigal National Park. The population at this site is disturbed and fragmented by land clearing for the Baha'i Temple, a carpark, residential properties and Mona Vale Road, which bisects the habitat.

Six months after the January 1994 fires, the section of the population within the Pittwater Council area numbered some 281 live adults, 544 dead adults and 428 seedlings on the north-western side of  Mona Vale Road, and several plants in the vicinity of Powder Works Road (Scott et al. 1995). The section of the population in Garigal National Park numbered an estimated 1400 seedlings in Garigal National Park on the south-eastern side of Mona Vale Road. The latter have now grown to maturity and formed a good-sized stand of adult plants.

Specimens at the National Herbarium of New South Wales, Royal Botanic Gardens Sydney, show that Grevillea caleyi has been present around the Baha'i Temple since at least 1963. Other specimens at the herbarium suggest that the species was once more widespread in Pittwater. However, the localities given for these specimens are imprecise and it is unclear whether they were collected in Pittwater or Warringah: specimens from 'Pittwater Road' collected in 1914 and 1917, and a specimen from 'Elanora Heights-Collaroy' collected in 1950.

Habitat

Typically, Grevillea caleyi grows on iron-rich lateritic soils on ridgetops (170-240 m above sea level). It is usually found in open-forest vegetation, generally dominated by Silvertop Ash Eucalyptus sieberi and Red Bloodwood Corymbia gummifera (Scott et al. 1995). This community, known as the Duffys Forest Vegetation Community, is listed as an endangered ecological community and is discussed below in section 2.6.1.

Grevillea caleyi is also occasionally found in more typical Hawkesbury Sandstone ridgetop vegetation, low woodland of Red Bloodwood and Broad-leaved Scribbly Gum Eucalyptus haemastoma. One stand is located in Hawkesbury Sandstone gully forest, dominated by Sydney Red Gum Angophora costata and Sydney Peppermint Eucalyptus piperita, but the species appears to have been introduced to this site, rather than a natural occurrence.

Ecology

Grevillea caleyi is an open, spreading shrub that may grow to about 4 m high and 4 m across. It does not usually flower and produce seeds before 2.5-5 years of age (Scott et al. 1995). Flowers are produced sporadically throughout the year with a peak flowering period in late winter and spring. The large 'toothbrush' flowers appear to be bird pollinated and may be self compatible.

Fruit maturation takes 2-3 months. Usually one large seed is produced per fruit. Fecundity is low with only about 3% of flowers resulting in seed. As individual plants age they produce more flowers and fruit. Seed dispersal is minimal. Upon maturity the fruits dehisce, dropping the seed to the ground beneath the parent plant. The viability of seeds is high and most are released in a dormant state.

Through time there is a slow loss of dormancy resulting in a fluctuating trickle of germination, though most seedlings do not survive in the undisturbed environment. Seeds are predated at the fruit stage by weevils and then on the ground after seeds are shed by Bush Rats and Swamp Wallabies. Adult plants senesce from 12-15 year onwards.

Grevillea caleyi is fire-sensitive and relies on germination from a soil seedbank to recover after fire. Seedlings are common after fire, or in open disturbed places. The seed dormancy mechanism is not fully understood and it is unclear how fire promotes germination. During the 1994 fires, some 60% of the total habitat of Grevillea caleyi was burnt and many population fragments now consist solely of plants that have germinated since the fires.

The number of plants in a population may thus fluctuate widely over short periods of time in response to fire or adult senescence. It takes some 8-12 years for the soil seedbank to reach a sufficient level to replace a population and so it is critical that the interval between successive fires is not less than 8-12 years at a site. Repeated fires at intervals of less than eight years may lead to the local extinction of Grevillea caleyi from a site. In sites unburnt for more than 15 years adult senescence may result in marked declines of the soil seedbank unless high levels of fecundity are maintained (Scott et al. 1995).

Management Issues

• Recovery plan - a plan has been prepared (Scott et al. 1995) and a recovery team established, on which Pittwater Council is represented, to implement the plan. A
  new recovery plan is in preparation to comply with the requirements of the Threatened Species Conservation Act
• Conservation of remnant bushland
• Habitat degradation in remnant bushland
• Fire management (as discussed above, fire is a major factor in the Grevillea caleyi life cycle)
• Preservation of remnant individuals in urban areas
• Loss of genetic integrity through hybridisation with planted Grevillea species
• Translocation (as an alternative to conservation in situ)
• Unauthorised collection of plant material
• Community education
• Lack of knowledge of the species (the species is relatively well known compared with other threatened plants in the area, but there are still gaps in our knowledge)

Updated: 06 Dec 2011