3.15 Haloragis exalata subsp. velutina Orchard
Haloragis exalata subsp. velutina is restricted to north-eastern New South Wales and south-eastern Queensland where it occurs from Kempsey north to the Bunya Mountains. It has a distribution range of approximately 370 km. There is no quantitative data on population sizes at the sites in Queensland. One locality within the Brisbane city area is considered to be extinct. Potential threats are invasion of habitat by exotic weed species and an inappropriate fire regime.
The genus Haloragis is placed in the family Haloragaceae. The genus is distributed from Australia to the south Pacific with approximately 28 species (Orchard 1990). In Australia it comprises approximately 23 species throughout the temperate and arid areas of the continent with a range of habits from ephemeral herbs to obligate aquatics (Orchard 1990).
Haloragis exalata subsp. velutina was formally described in 1975 based on material collected near Grafton in northern New South Wales (Orchard 1975). The botanical description of Haloragis exalata subsp. velutina is as follows:
Small erect shrub to 1.5 m tall. Stems 4-angled, finely and densely velvety with hairs less than 0.01 mm long. Leaves opposite, becoming alternate below inflorescence, sessile or shortly petiolate, narrowly lanceolate, minutely serrate with 30-40 teeth in distal part or entire, finely and densely velvety with hairs less than 0.01 mm long; lamina 55-60 mm long 6-8 mm wide; petiole 5-10 mm long. Inflorescence of 3-7 flowered dichasia; pedicels 0.7-1.5 mm long. Sepals ovate to deltoid, 0.6-0.8 mm long. Petals 2.4-3.3 mm long yellow-green to reddish. Fruit ovoid to obpyriform, 2-2.5 mm long, 4-ribbed, smooth or weakly rugose between ribs, finely and densely velvety with hairs less than 0.01 mm long (Orchard 1990). For a more detailed description refer to Orchard (1975 & 1990).
Haloragis exalata can be distinguished from other species of Haloragis by its opposite vegetative leaves at least on the lower stems which have a thin, entire narrowly lanceolate to oblong lamina, toothed inflorescence bracts, and 4-locular ovary and fruit. Haloragis exalata subsp. velutina differs from Haloragis exalata subsp. exalata by having a dense velvety indumentum and narrower petiolate leaves with a finely serrate or almost entire margin (Orchard 1990).
Haloragis exalata subsp. velutina 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) and is also listed on Schedule 1 Part 2 (vulnerable) of the Commonwealth Endangered Species Protection Act 1992.
3.15.4 Distribution and abundance
H. exalata subsp. velutina is restricted to south-eastern Queensland and north-eastern New South Wales where it occurs from Kempsey north to the Bunya Mountains. It has a distribution range of approximately 370 km. H. exalata subsp. velutina was not surveyed during the present study. Details from Queensland Herbarium specimens of H. exalata subsp. velutina are listed in Appendix 1.14. In Queensland five collections have been recorded. One early collection was made from a swamp in Hamilton, Brisbane. The habitat in the Hamilton area has been cleared and it is expected that this population has become extinct. Two other early records come from the Bunya Mountains, one clearly within Bunya Mountains National Park. Two recent collections have be made in SF 151 Fty 824 and SF 637 Fty 1613. There is no information available on population sizes at the sites.
H. exalata subsp. velutina has been recorded growing in rainforest, on rainforest margins and from Poa-Themeda grassland adjacent to rainforest at altitudes above 500 m. It is also recorded from swampy terrain at elevations just above sea level.
3.15.6 Life history and ecology
There is little recorded information on the ecology and life history of the species. Haloragis exalata subsp. velutina is a slender open shrub that reproduces by sexually produced seeds. There is no indication that the species can reproduce vegetatively, however, some species of Haloragis are reported to be able to sucker (Elliott and Jones 1990).
Haloragis exalata subsp. velutina has been recorded flowering in February and April and with fruits in April. Pollinators are unknown but are suspected to be insects. The fruit is a indehiscent nut that falls from the plant when mature. There appear to be no adaptations for secondary dispersal by animals. The longevity and viability of the seed is unknown. Seed are reported to be slow to germinate, but some begin to germinate 15-20 days after sowing (Elliot and Jones 1990).
The response of the plant to fire and disturbance is not known. Haloragis exalata subsp. velutina above-ground biomass is probably killed by fire. It is not known whether this species is capable of regenerating from its rootstock. Elliot and Jones (1990) report that some Haloragis spp. readily colonize areas which have been disturbed.
With our limited knowledge of the species it is difficult to determine the stability of the populations and what possible threats there are to the long term existence of H. exalata subsp. velutina in the wild. The populations on rainforest margins may be susceptible to invasion by exotic weed species such as lantana (Lantana camara) into the habitat. The population recorded in the grassland community in the Bunya Mountains is also threatened by the invasion of exotic plant species. The introduced grasses kikuyu (Pennisetum clandestinum) and African lovegrass (Eragrostis curvula) are considered to have the potential to become major problems in maintaining the natural flora of the Bunya Mountain grasslands (Fensham and Fairfax 1996b). Kikuyu has already invaded two grassland patches displacing the native grasses and has been recorded in another two grassland patches (Fensham and Fairfax 1996b).
3.15.8 Management, research and conservation measures
Previously recorded sites should be examined to establish their size and extent of populations. Areas of likely habitat in the vicinity of the known populations should be searched for further occurrences.
It is important to understand how H. exalata subsp. velutina responds to differing fire regimes in its habitat. Research is required into the fire ecology, reproduction biology and the population dynamics of the species.
Monitoring and control of the spread of the weeds should be undertaken. Fensham and Fairfax (1996a) recommended that kikuyu and African lovegrass be eradicated where possible from the grassland communities. Ongoing monitoring of the impact of weeds on the communities is required.