Genetic comparison between Victorian and Tasmanian populations of Prasophyllum correctum D.L. Jones (Orchidaceae) suggests separate species L. A. Orthia 1 , R. C. Garrick 1 and E. A. James 1,2 1 Genetics Department, La Trobe University, VIC. 3086. 2 National Herbarium of Victoria, Royal Botanic Gardens Melbourne, Private Bag 2000, VIC. 3141. Abstract Genetic variation within and between Tasmanian and Victorian populations of the Gaping Leek Orchid Prasophyllum correctum (Orchidaceae) was investigated using the Random Amplified Polymorphic DNA (RAPD) method. The degree of fixed genetic differences between the two populations was substantial, suggesting that each population constitutes a different species. The Tasmanian population contained very little genetic variation, indicating that asexual reproduction or self-fertilisation may be the predominant reproductive mode, but this population does not appear to be clonal. Individuals from the Victorian population exhibited high levels of genetic variation relative to those from the Tasmanian population. These findings suggest that the Victorian and Tasmanian P. correctum populations ought to be managed separately, and cross-pollination or translocation should be avoided, because of the lack of genetic similarity between them. Keywords: Prasophyllum, RAPD, genetic variability, conservation Introduction The Gaping Leek Orchid, Prasophyllum correctum D.L. Jones, is a small terrestrial orchid from southeastern Australia. Prasophyllum correctum (Jones 1994) was believed to be endemic to Victoria until plants collected in 1995 from the Campbell Town golf course in Tasmania were identified as P. correctum (Jones 1998). The species is believed to have formerly been widespread throughout lowland Gippsland, but it is currently restricted to two small populations located near Munro and Lindenow South in protected rail reserves (Hoey & Lunt 1995) in Themeda triandra Forssk. grasslands or Eucalyptus tereticornis Sm. ssp. mediana grassy woodlands, which are recognised as endangered ecosystems in Victoria (Coates et al. 1999). In Tasmania, the species was known only from the Campbell Town golf course (Hoey & Lunt 1995; Jones 1998) until a single plant was found 7–8 km away in 1999 (Fig. 1). The presence of this outlier is considered to be reasonable confirmation that the species was more widespread before the Tasmanian midlands were opened up for agriculture (Threatened Species Unit 2000). In Victoria, Prasophyllum correctum is listed as threatened under the Flora and Fauna Guarantee Act 1988 and has ROTAP code 2E (Briggs & Leigh 1996) with as few as 127 plants estimated to remain (Coates et al. 1999). The demise of the species has been attributed to habitat degradation through grazing and clearing for agriculture (Backhouse & Jeanes 1995; Hoey & Lunt 1995). Current threats to the continuing existence of Victorian P. correctum include rail reserve maintenance (e.g. rotary hoeing or slashing), grazing and trampling by roaming stock and feral animals, weed invasions, competition from native plant species, and herbicide use (Backhouse & Jeanes 1995; Hoey & Lunt 1995; Coates et al. 1999). In contrast, the Tasmanian population is estimated to contain at least 1000 individuals (Coates et al. 1999), and appears to be relatively stable in its unusual habitat of the Campbell Town golf course rough. But this population is still sufficiently threatened such that the species is listed as endangered under the Tasmanian Threatened Species Protection Act 1995, and under the federal Environment Protection and Biodiversity Conservation Act 1999. Although the site is not formally reserved, it is Muelleria 18: 79–87 (2003)