Survey of threatened plant species in South East Queensland biogeographical region queensland cra/rfa steering committee survey of threatened plant species in
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3.11 daviesia discolor pedley3.11.1 SummaryDaviesia discolor is known from two disjunct localities approximately 350 km apart, Blackdown Tableland, 180 km south west of Rockhampton and the Coast Range, approximately 70 km west of Maryborough. The Blackdown Tableland sites have not been assessed in the present survey. The total population of D. discolor is estimated to be 17800 plants in the Coast Range sites over an area of approximately 2.5 hectares. It grows in very tall open forests on hillcrests and gently to very steeply inclined hillslopes between 500-580 m above sea level. The soils are derived from rhyolite and are well drained, shallow, brownish black sandy loam to sandy clays with an acidic reaction. Potential threats to the survival of D. discolor arise from human interference in the environment. The main threat is an inappropriate fire regime. It has been recommended that populations be monitored to obtain information on ecology of the species and to gauge the impact of habitat management for grazing. 3.11.2 Species description and identificationThe genus Daviesia is endemic to Australia and is the second most diverse genus in the pea family (Fabaceae) in Australia with 121 species distributed throughout the states. The centre of diversity is in south west Australia (Crisp 1995). Daviesia discolor Pedley was formally described in 1977 from material collected on Blackdown Tableland, approximately 170 km west south west of Rockhampton (Pedley 1977). D. discolor is part of the D. latifolia group within the subtribe Mirbelieae (Crisp 1991). A botanical description of Daviesia discolor is as follows: Multi-stemmed shrub to 2 m high, glabrous. Branchlets ascending, angular, ribbed. Phyllodes spirally arranged, ascending to widely spreading, linear-elliptic, more or less falcate, attenuate at both ends, articulate at base, 40-160 mm long, 4-11 mm wide, striate with fine, somewhat prominent, reticulate venation, thin, green, discolorous. Racemes 1 or 2 per axil, 3-8 flowered; rachis 2.5-10 mm long; bracts more or less appressed to pedicels, 3.5 mm long, Calyx 3.6-4.0 mm long, ; lobes 0.6-1.0 mm long, upper two very broadly triangular, lower three triangular, more deeply cleft. Corolla: Standard very broadly ovate, emarginate, 5.5-5.9 mm long, 6.5-7.3 mm wide, yellow with dull red markings surrounding an intensely yellow bilobed spot at the centre; wings obovate-oblong, rounded at apex, 5.4-5.9 mm long, 1.9-2.5 mm wide, yellow towards apex, dull red towards base; keel half very broadly obovate, scarcely acute, saccate, auriculate, 4.4-4.6 mm long, 1.9-2.1 mm wide, pale green with dull red tip. Pod obliquely broadly triangular, compressed, acute, with upper suture nearly straight, 7.0-8.5 mm long, 5.5-6.0 mm wide, thin-walled (Crisp 1991). (see Plate 2 & 3). In the past D. discolor has been misidentified as D. mimosoides but is distinguishable from this species by its narrower, longer and discolorous leaves. D. discolor is closely related to and resembles the more common species D. arborea from northern New South Wales and southern Queensland. D. discolor can be distinguished from D. arborea by its habit, bark, inflorescence and flower features (Crisp 1991). Details of these differences are presented in Table 3.11.1. Table 3.11.1. Characters distinguishing Daviesia discolor and Daviesia arborea.
3.11.3 Current conservation statusDaviesia discolor 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. 3.11.4 Distribution and abundanceDetails from Queensland Herbarium specimens of D. discolor are listed in Appendix 1.10. Altogether 10 specimens of D. discolor have been collected from two disjunct localities approximately 350 km apart. As far as can be ascertained, this distribution pattern is natural and is not related to habitat reduction or fragmentation from human activity. It has been recorded from Blackdown Tableland (seven specimens), 180 km south west of Rockhampton and the Coast Range (3 specimens) near Biggenden, approximately 70 km west of Maryborough. The Blackdown Tableland sites have not been assessed in the present survey but it is believed that D. discolor occurs within both the National Park and State Forest areas on the tableland. Notes on herbarium specimens indicate the species was common at one of the sites in 1990. D. discolor has been observed at 2 sites (Mt Walsh N.P. and SF 1344 (Fty 1534))on the Coast Range which are approximately 1.5 km apart. Detailed locality data for each site is presented in Appendix 2.2. The estimated populations for the two sites are presented in Table 3.11.2. The total population of D. discolor at the two sites is estimated to be 17800 plants over an area of approximately 2.5 hectares. The population within Mt Walsh National Park is the larger of the two populations with 90 % of the total population. Table 3.11.2. Estimated abundance and area of occupancy for daviesia discolor sites on the coast range. Where abundance was estimated by random transect sampling a mean value and lower and upper 95% confidence limits are given.
The populations consisted of individuals up to 1.5 m high. No seedlings were observed in burnt or unburnt areas of the populations. Both populations appear generally healthy. 3.11.5 HabitatOn the Blackdown Tableland D. discolor is reported to occur on sandy soils derived from sandstone and on lateritic clay soils at elevations of 600-900 m above sea level (Crisp 1991). The Coast Range sites are situated in mountainous terrain on hillcrests and gently to very steeply inclined hillslopes generally with a southerly to easterly aspect and at elevations between 500-580 m above sea level. The soils are well drained, shallow, brownish black sandy loam to sandy clays with a pH 5.5-6.1. The geology is mapped as Johngboon Rhyolite. The vegetation community is a very tall open forest. The common canopy species are Corymbia trachyphloia and Eucalyptus acmenoides. Other tree species present included Eucalyptus major, E. montivaga and E. decolor. The shrub and ground cover at the two sites contrast in density. The Mt Walsh N.P. site has a dense shrub and ground cover with the common species being D. discolor, Logania albiflora, Lophostemon confertus and the ferns Calochlaena dubia and Pteridium esculentum. The site in SF 1344 which appears to be the drier of the two sites has a much more open shrub and ground layer. The common species present included Jacksonia scoparia, Imperata cylindrica, Podolobium ilicifolium and Themeda triandra. No exotic weed species were observed at either site, although Lantana camara is a common weed in the vicinity of these populations. The Mt Walsh N.P. site was undisturbed, while cattle grazing is presently occurring in the vicinity of the population within SF 1344. There was no evidence that D. discolor was grazed by cattle. 3.11.6 Life history and ecologyThere have been no studies into the biology or autecology of Daviesia discolor. The majority of the following information is extrapolated from our understanding of other species of Daviesia. D. discolor is not known to be in cultivation but a number of Daviesia species are cultivated at Australian National Botanic Gardens, Canberra (Wrigley and Fagg 1996, Elliot and Jones 1984). Daviesia is readily propagated from scarified seed (Wrigley & Fagg 1996). Seed of some species can be difficult to obtain because of the destruction of immature pods by insects (Elliot and Jones 1984). Some species have been grown from cuttings, but it is often difficult to obtain suitable material. Vigorous young growth which has just started to become firm seems the most suitable (Elliot & Jones 1984). General requirements for cultivation of Daviesia are for a well-drained light to medium soil, in a situation that receives partial to full sun. Daviesia discolor is a phyllodenous shrub with an unknown life span. The main method of reproduction is by sexually produced seeds. D. discolor has been recorded flowering from August to September and fruiting in October. Possible pollinators were not observed during the field work. However, the Fabaceae family is principally a bee-pollinated family (Kalin Arroya 1981). Soon after maturing the pod splits to release a single seed or possibly two. The opening of the fruit forcibly ejects the seed. The dispersal distance achieved by this mechanism is unknown. I have not seen mature seed of D. discolor, but from the examination of immature seed it appears that this species has a fleshy attachment on outside of the seed coat. Such attachments are known in many genera in the Fabaceae and it is suggested that these structures promote secondary dispersal of seed by ants (Berg 1975). Other species of Daviesia as with most leguminous plants release their seed from the fruit in a dormant state (Elliott and Jones 1984, Auld and O’Connell 1991). It is highly probable that D. discolor produces similar seeds. For most hard-seeded leguminous species the dormancy is due to seed coat impermeability. The germination of such seeds involves the breaking of the seed dormancy by heat or the gradual decay of the seed coat. With these seed characteristics D. discolor would accumulate a persistent soil seed bank during inter-fire periods. The longevity of such a soil-stored seed bank is unknown. The above-ground structures of D. discolor are killed by fire. However, regeneration can occur from the rootstock and lateral roots (see Plate 4). 3.11.7 ThreatsFires are either accidental (wildfires from lighting strikes or fires from surrounding agricultural lands) or planned (hazard reduction burns). The occurrence of fire in the habitat of D. discolor should not be viewed as being incompatible with the long term survival of the species. However the lack of ecological information about this species response to fire makes it impossible to assess what would be an appropriate level of frequency and intensity for the long term benefit of the species. If fires are too frequent, the plants will have insufficient time to build-up a soil seedbank to replace plants that are killed in the fire. Even through this species is capable of regenerating from rootstocks a high fire frequency would eventually lead to population declines. There is no evidence to suggest that the grazing of cattle in the habitat of D. discolor affects the species directly. However, the use of the habitat for cattle grazing may indirectly affect the species though the use of regular fires for the promotion of grass in the understorey. 3.11.8 Management, Research and Conservation MeasuresThere is no quantitative data to indicate that the populations of D. discolor have declined in the past or are presently declining. However, appropriate management practices need to be put into place to ensure the long-term survival of D. discolor. The main habitat management issue is assessing the impact of present fire and grazing regimes. The lack of understanding concerning the ecological requirements of this species is a major shortcoming for future management of the habitat. Research should be encouraged to determine relevant aspects of the biology and ecology of D. discolor. Monitoring should be designed to gather fundamental information to determine the effects of management on population and community dynamics. Further surveys are needed in the populations on the Blackdown Tableland to consolidate the available information with respect to known populations and potential threats to these populations. D. discolor assessed against the IUCN (1994) criteria for threatened wildlife falls into the category of Vulnerable, ie. is facing a high risk of extinction in the wild in the medium-term future, as defined by criteria D.2. Its population is characterised by an acute restriction in its area of occupancy (typically less than 100 km2) or in the number of locations (typically less than 5). The present status of Vulnerable for D. discolor is considered to be appropriate. |