Outlines are presented of 32 threatened plant species, of which 10 species have been surveyed in some detail during the present project. The species are arranged alphabetically.
3.2 Acacia attenuata Maiden & Blakely
Acacia attenuata is restricted to coastal sandplains from just north of Bundaberg to Burleigh on the Gold Coast. It covers a range of approximately 400 km and encompasses an area of occurrence of approximately 12,000 km2. It has been recorded from State Forest (SF) 898, Littabella, Poona and Cooloola National Parks, and Burleigh Knoll and Palmview Conservation Parks. The species is also reported to be present in the Mooloolah River National Park. No information is available on population size. Current or perceived threats to the continued survival of A. attenuata are considered to be loss of habitat and inappropriate fire regimes.
3.2.2 Species description and identification
The genus Acacia is placed in the family Mimosaceae. Acacia is widespread throughout the tropical and subtropical regions of the world (excluding Europe) with approximately 1200 species (Mabberley 1997). In Australia it comprises approximately 900 species of shrubs and trees, which are widely distributed throughout the continent with a large range of foliage and flower types.
Acacia attenuata Maiden & Blakely was formally described in 1927 from material collected near Beerwah, approximately 77 km north of Brisbane (Maiden & Blakely 1927). The botanical description of Acacia attenuata is as follows:
A slender shrub to about 3 m tall, retaining juvenile foliage for long period and even flowering and fruiting in juvenile state; branchlets somewhat angular, soon becoming terete, glabrous. Stipules very broad triangular, ca 0.4 mm long, early deciduous; pulvinus 3-5 mm long; phyllode more or less straight, apex obtuse mucronulate or occasionally acute, base attenuate, (9)10-14(17) cm long, 7-16 mm wide, 7-14(18) times as long as wide, glabrous; midrib prominent, curved and
approximating ventral margin 1/10 to 1/4 the length of the phyllode from the base; gland inconspicuous, immediately above the pulvinus. Heads of 20-35 flowers in glabrous axillary 6-14-branched racemes, the axis 5-7.5 cm long, the peduncles ca 7 mm long, bracteoles peltate; flowers cream-yellow, 5 merous. Pod flat slightly narrowed between seeds and raised above them alternately on each side, glabrous 8-10 cm long, 13-14 mm wide; seeds longitudinal, oblong, 6-7 mm long, 3-4 mm wide, the funicle encircling the seed (Stanley & Ross 1983). For a more detailed description refer to Pedley (1978). For an illustration see Maiden & Blakely (1927).
Acacia attenuata is most closely related to and strongly resembles A. rubida in retaining its juvenile leaves for a long period of time. However, A. attenuata differs from A. rubida by having more attenuated phyllodes, with the relatively smaller, different-shaped and strictly basal gland and a much broader pod. A. attenuata may be confused with the more widespread and common A. falcata but can be distinguished by its narrower, more or less, straight phyllodes and broader pods.
Acacia attenuata Maiden & Blakely is presently listed on the schedule of the Queensland Nature Conservation Act 1992 as “vulnerable wildlife”. The species has been assigned a national conservation status of V (vulnerable) by ANZECC (1993). It is also listed on Schedule 1 Part 2 (vulnerable) of the Commonwealth Endangered Species Protection Act 1992.
3.2.4 Distribution and abundance
Acacia attenuata was not surveyed during the present study. A. attenuata is endemic to south east Queensland. It occurs on sandplains not more than 30 km from the coast with a range along the coast of approximately 400 km from just north of Bundaberg to Burleigh on the Gold Coast. It has never been recorded on any of the islands along the coast in this region.
Details from Queensland Herbarium specimens of A. attenuata are listed in Appendix 1.1. A total of 34 specimens have been collected from approximately 23 sites. Twelve of the earliest records (prior to 1960) give only a general locality, which is insufficient to accurately relocate the collection sites.
A. attenuata is recorded from Littabella National Park (N.P.) (2 records), Poona N.P. (2 records), Cooloola N.P. (1 record), Burleigh Knoll Conservation Park (C.P.) (1 record) and Palmview C.P. (1 record). The species is also reported to be present in the Mooloolah River N.P. with the endangered species Eucalyptus conglomerata (Drake 1995). A. attenuata has been recorded from SF 898 (Fty 1636) (1 record) where it is reported to be common at the site of collection (Queensland Herbarium database).
There is no information available on population sizes.
A. attenuata is restricted to the coastal lowlands. It occurs on flats, low rises and at the edge of wallum swamps. The soils are sandy and mostly poorly drained. A. attenuata has been recorded growing in shrublands with Leptospermum whitei and Baeckea frutescens, wallum with Banksia aemula and Eucalyptus robusta, woodlands with Corymbia trachyphloia, Eucalyptus umbra and Banksia oblongifolia, and open forests of Eucalyptus umbra, E. racemosa and Melaleuca quinquenervia. A. attenuata has also been recorded on roadsides and in areas previously cleared of natural vegetation.
Acacia attenuata is a perennial shrub reaching 3 m high. The longevity of individual plants is unknown. The main method of reproduction is by sexually produced seeds. The species is not known to be capable of resprouting from the stem base or other underground organs.
Flowering has been observed from May to September. No pollinators have been reported for A. attenuata. However studies of pollinators of other Acacia species indicate they are primarily insect pollinated (Bernhardt 1989). Fruits have been recorded from August to September. The fruit splits soon after maturing, releasing the seeds. It is not known if the opening of the capsule forcibly ejects the seed or whether the seeds just fall to the ground. The seed has a fleshy attachment on the outside of the seed coat. It is suggested that such attachments promote secondary dispersal by ants (Berg 1975).
When released from the mature pods, seeds are dormant. As with most hard-seeded leguminous species, this dormancy is due to seed coat impermeability. The genus Acacia contains numerous species whose germination is promoted by heat from fire. With these seed characteristics, A. attenuata would accumulate a persistent seed bank in the soil during inter-fire periods. The length of seed viability in the soil is unknown.
Fire is a major environmental factor in Australia, particularly in dry sclerophyll forest. Different intensities, frequencies and seasonal occurrences of fire will effect the population dynamics of this species. Although little is known about the fire ecology of A. attenuata, it is suggested that fire plays an important role in the recruitment pattern of this species. There is no information available on this species’ fire requirements.
There have been in the past large tracts of habitat cleared for urban development and agricultural development. Some habitat may have been lost with development of softwood plantations in the Beerwah and Maryborough areas. Clearing and drainage of habitat for urban development is continuing to occur especially in the south of its range on the Gold and Sunshine Coasts.
An inappropriate fire regime would lead to a decline in the ability of the species to maintain sustainable recruitment patterns. The limited knowledge about the effect of fire and species response makes it difficult to assess the total impact of varying fire regimes. However, too frequent a fire regime would certainly lead to a gradual decline in the population. Sufficient time would be required between fires to allow seedlings to flower and replenish the soil seedbank. Sufficient soil heating is also needed during fires to break seed dormancy and allow germination.
Additional survey work is required to determine what populations remain and what would be the most appropriate course of action for conserving the species. Areas worthy of investigation include SF 915 (Fty 1592), SF 561 (Fty 1655) and the Burrum Coast National Park.
Fire intensity, frequency and seasonality are important factors in determining the long term population levels of most hard-seeded leguminous species. It is important to understand how A. attenuata responds to differing fire regimes in its habitat. Research is required into the fire ecology, reproduction biology and the population dynamics of the species.