Memoirs of the Museum of Victoria 56(2):597-603 (1997) 28 February 1997 https://doi.org/10.24199/j.mmv.1997.56.56 CONSERVATION OF NATIVE EARTHWORMS AND THE ROLE OF THE GIANT GIPPSLAND EARTHWORM AS A FLAGSHIP TAXON. B. D. Van Praagh Invertebrate Survey Department, Museum of Victoria, 71 Victoria Crescent. Abbotsford, Vic. 3067, Australia Abstract Van Praagh, B.D., 1997. Conservation of native earthworms and the role of the Giant Gippsland earthworm as a flagship taxon. Memoirs of the Museum ofVietoria 56(2): 597- 603. Very little is known of the Australian native earthworm fauna, which has been largely replaced by introduced species in most disturbed areas. The Giant Gippsland Earthworm, Megascolides OustraliS, is one of the better known earthworm species and has aroused public curiosity and sympathy due to its gigantism and restricted distribution. The role of M. auslralis as a flagship taxon is discussed in terms of its wider value in the conservation of other earthworm species. Introduction Wood (1974) stated that 'it is surprising that more is known about the abundance of intro- Australia has a very diverse indigenous earth- duced Lumbricidae in New Zealand and Aus- worm fauna arising from its long geographical tralia than that of the native Megascolecidae' isolation (Lee, 1985), but little detailed infor- and more than 20 years later this observation mation exists on the ecology, distribution or still applies. This paper discusses the conser- conservation status of any native species vation status of Australian earthworms and the (reviewed by Lee, 1985, Kingston and Dyne, role of the famous Giant Gippsland Earthworm 1996). only species of native earthworm The as a flagship taxon in promoting the conser- date is the Giant Gipps- studied in any detail to vation of native earthworm fauna. land Earthworm, Megascolides australis McCoy the first Australian (Van Praagh, 1992, 1994), Australia's earthworm fauna native earthworm to be described. Most avail- to the able information regarding native earthworms All Australian native earthworms belong Megascolecidae (Kingston and Dyne, lies in the taxonomic and biogeographic litera- family mainly southern hemisphere group ture (e.g., McCoy, 1878; Spencer, 1888; Jamie- 1996) a and Central America, son, 1981; Dyne, 1984; Abbott, 1994). Museum which occurs over South Asia. Approximately 325 collections are also a valuable source of ecologi- Africa and south-east species, belonging to 28 cal information on species through the provision native earthworm have been described from Australia of details of habitat or locality data. genera, Much information on the ecology of earth- (Kingston and Dyne, 1996). However, knowl- indigenous earthworms in different worms deals primarily with species belonging to edge of the with the earthworm fauna of West- the European family Lumbricidae which States varies, and the Northern Territory par- includes the introduced earthworm species com- ern Australia poorly known (Abbott, 1994). For monly encountered in Australian gardens. The ticularly 12 species of earthworms have introduced lumbricid Lumbricus terrestris example, only illustrate a been described from the Northern Territory (R. Linnaeus, is still commonly used to Blakemore, pers. comm. 1996). Extrapolation of 'typical earthworm' in Australian biology classes of new species found from recent and most biology textbooks. Ironically, the exist- the number to surveys by Kingston and Dyne (1996) indicate ence of this species in Australian soils has yet the number of native earthworm species in be confirmed (R. Blakemore pers. comm. 1 995). that is probably well over 1000. The assumption that information obtained for Australia recent examination of nearly 2000 lumbricids can be transferred directly to megas- In a major differ- museum and literature records, Abbott (1994) colecids is unjustified when the geological mapped the distribution of the native earth- ences in soils, vegetation types and Northern worm fauna of Australia and found the major history between Australia and the limiting earthworm distribution was rain- Hemisphere are considered (Abbott, 1985b). factor 597 598 B.D. VAN I'RAAGH fall. Earthworms were generally absent in facing slopes. Anecdotal information regarding regions where rainfall was less than 400 mm. historical distribution patterns suggests that However, 30 records of earthworm distribution numbers have declined and the range of the occurred in areas receiving less than 400 mm. At species has contracted through vegetation clear- least 16 of these were found to be surviving ance and farming practices, particularly plough- under favourable situations such as waterholes, ing (Smith and Peterson, 1981; Van Praagh, moist caves, permanent rivers and farm dams 1994). Protection of native earthworms may be (Abbott, 1994). particularly important for species that have a Changes in soil and vegetation resulting from restricted distribution or are naturally rare. European settlement have led to destruction of Listing of threatened earthworms some of our indigenous earthworm fauna and to Worldwide, three species of giant worms, four major changes in the distribution and compo- genera of South African Acanthodrilinae and sition of earthworms in Australian soils. In gen- two genera of South African microchaetids are eral, native earthworm species do not survive listed by the International Union for the Con- the change from native bush to pasture (Lee, servation of Nature (IUCN) Invertebrate Red 1961, Wood, 1 974) and the predominant family Data Book (Wells et al., 1983). The endemic in cultivated soil in southern temperate Aus- Acanthodrilinae of South Africa comprise some tralia is the introduced Lumbricidae (Baker et 90 species, most of which are regarded as threat- al., 1992a). In disturbed areas of tropical Aus- ened (Ljungstrom, 1972) since they are pre- tralia, the native earthworm fauna is largely dominantly litter species restricted to indigen- replaced by a small group of earthworms from ous forests which have been reduced to about the families Glossoscolecidae and Megascoleci- 0.3% of their original range for agriculture or dae, originally from South and Central America, exotic plantations (Ljungstrom, 1972, Wells et Africa and south-east Asia (Lee, 1991). al., 1983). Microchaetus spp. and Triogenia spp. (Microchaetidae) are characteristic of sandy and Conservation of earthworms clayey soils of primary grasslands and sav- annahs. Agricultural practices have reduced the Vulnerability available areas of suitable habitat by overgraz- Apart from a recent discussion of the conser- ing, lowering of the water table and desertifica- vation of the earthworm fauna of the wet tropics tion of the savannas (Reinecke, 1983, Wells et of Queensland by Dyne and Wallace (1994), the al., 1983). The microchaetids includes the giant conservation status of Australian earthworms is Microchaetus michrocaetus Rapp which is poorly known. Many have extremely limited thought to be one of the largest earthworms in geographical distributions and may be highly the world. In Australia, two oligochaetes are specialised suggesting tolerance to only a narrow documented on threatened species lists. M. aus- range of soil conditions. For example, Dyne tralis is listed as vulnerable under the Depart- ( 1 99 1 a) found Digaster nothofagi Jamieson only ment of Conservation and Natural Resources from a look out in Warrie National Park, threatened species list (CNR, 1995) and as Queensland, in apparently uniform and con- threatened under Victoria's Flora and Fauna tinuous rainforest cover. More recently. Dyne Guarantee Act ( 1 988) (Flora and Fauna Guaran- and Wallace (1994) found 45% of new species tee Scientific Advisory Committee, 1991) and found in the wet tropics of Queensland's world the Lake Pedder earthworm is listed as heritage area from only single sites. The Lake endangered under the Tasmanian rare or Pedder earthworm, Diporochaeta pedderensis threatened species list (Invertebrate Advisory Jamieson, was described from a single specimen Committee, 1994), but is thought to be collected in 1971 from the beach psammon of extinct. Lake Pedder in Tasmania. Subsequent searches for the species following the flooding of Lake Threats to earthworms Pedder in 1972 failed to find any specimens Vegetation Clearance. Since European settle- (Dyne, 1 99 1 b). Earthworms appear to be highly ment, there has been complete conversion of susceptible to environmental disturbance. In whole land systems to the growing of wheat and Victoria, The Giant Gippsland Earthworm, improved pastures (Frood and Calder, 1987). Megascolides australis is restricted to approxi- Native earthworms are rarely found in culti- mately 40 000 ha of the Bass River Valley and is vated soils (Wood, 1974; Abbott and Parker; extremely patchy within this area, being mainly 1 980, Baker et. al, 1 992a. b, 1 995; Kingston and confined to creek banks, gullies and some south Temple-Smith, 1988; Tisdall, 1985; Mele, CONSERVATION OF NATIVE EARTHWORMS S99 1991). The conversion of land systems to cane Dyne, 1991a). For example, the giant rainforest farming in Queensland is thought to have species Disaster longrMUli Boardman, found at resulted in the extinction of some earthworm depths of 0.8-1.5 m, is occasionally reported species (Wells et al., 1983). from areas where its original rainforest veg- Reasons for the disappearance of native earth- etation has been completely removed and is now worms after cultivation are unknown but may be used for cultivation or housing (Dyne,