Green and Golden Bell Frog - Taxonomy

Taxonomy

The common name, "Green and Golden Bell Frog", was first adopted by Harold Cogger in his 1975 book Reptiles & Amphibians of Australia. Before this, its common names were "Golden Frog" and "Golden Treefrog". The Green and Golden Bell Frog have many physical and behavioural characteristics representative of ranids; hence its original classification as Rana. It has a pointy snout, long legs, and almost complete toe webbing; the tympanum is large and distinct; and the overall body shape is similar to many Rana species. Like many frogs in the Rana genus, Green and Golden Bell Frogs are mostly aquatic, and only travel over land during periods of rainfall. It was removed from the genus because of anatomical differences with the family Ranidae. The bone and cartilage structural formations of the Green and Golden Bell Frog are closest to those of species in the family Hylidae; it was therefore reclassified.

The Green and Golden Bell Frog was first described as Rana aurea by Lesson in 1827. It has changed classification 20 times; it was first named Litoria aurea in 1844 by Günther, and changed another nine times before being named again as Litoria aurea. The specific epithet aurea derived from the Latin aureus for 'golden'. The species is now classified within the Litoria aurea complex, a closely related group of frogs in the Litoria genus. This complex is scattered throughout Australia: three species occur in south-east Australia, one in northern Australia, and two in Southwest Australia. The complex consists of the Green and Golden Bell Frog (Litoria aurea), Growling Grass Frog (Litoria raniformis), Yellow-spotted Bell Frog (Litoria castanea), Dahl's Aquatic Frog (Litoria dahlii), Spotted-thighed Frog (Litoria cyclorhyncha) and the Motorbike Frog (Litoria moorei). The ranges of L. raniformis and L. castanea overlap with the Green and Golden Bell Frog; this as well as physical similarities may make it difficult to distinguish between the species, and up until 1972, L. raniformis and the Green and Golden Bell Frog were regarded as the same, when electrophoretic studies proved them to be distinct. The Tablelands Bell Frog has not been seen since 1980 and may now be extinct, although the large yellow spots present on its thighs help distinguish it from the Green and Golden Bell Frog. The Growling Grass Frog, which is very similar to the Green and Golden Bell Frog, can only be readily distinguished by raised bumps on the dorsal surface. It has also been proposed that some populations of Litoria aurea located near Ulong, New South Wales, be a separate species Litoria aurea ulongae, but this was not accepted.

Litorea aurea is equally and most closely related to Litoria castanes and Litoria ranaformis. A micro-complement fixation technique using serum albumins has indicated that the species closest to Litoria aurea is Litoria ranifomis. Albumin immunological distance data suggest no differentiation between Litoria ranifomis and Litoria castanea, and that the Green and Golden Bell Frog evolutionally separated from the other two species about 1.1 million years ago. A 1995 study of protein variations showed that 4 of 19 protein systems had variation and only two had differentiation. Scientists believe that the different species can still hybridise as their distribution areas stll overlap, and both raniformis and aurea have been seen sharing ponds in the Gippsland area of Victoria. However, there has been little evidence of hybridisation actually occurring. Although there have been reports of frogs of mixed appearance in Gippsland, analysis of proteins and serums of the frogs showed two distinct species. Samples in other area of distribution have shown no evidence of hybridisation in spite of co-habitation.