The cause(s) of the apparent declines observed in populations of all taxa within the L. aurea complex are unclear (Gillespie, Osborne and McElhinney 1995). Investigations of disappearances among the group have primarily focused on L. aurea and L. castanea and two major directions in research have been pursued: the role of increased ultraviolet radiation; and the impact of the introduced fish, Gambusia (Mahony 1999). As for L. aurea, L. raniformis has disappeared from sites where Gambusia is present (Mahony 1999; W. Osborne pers. comm.). The dates of introduction of Gambusia to many regions are not well documented and this lack of information has hampered research into declines (Mahony 1999). Introduced Gambusia fish are also a threat to the introduced populations in New Zealand. It is also possible that disease, such as a viral infection or chytrid fungus, may have contributed to the decline of some species (W. Osborne pers. comm.). Chytrid fungus was detected in this species in Mount Compass, South Australia, but was first identified in New Zealand from populations of this species in Christchurch. The drainage of wetlands in Tasmania is a particular threat.
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