Dunnarts demonstrate value of collection


Dunnart skins showing the greyer belly of the grey-bellied dunnart (top) when compared to the little long-tailed dunnart (bottom).

The Terrestrial Mammal group at the South Australian Museum has discovered a species of dunnart not previously recorded in South Australia. The exciting discovery has highlighted that collecting voucher specimens and tissues remains a critical part of biological surveys. Vouchers are specimens of an animal or plant that are housed indefinitely in a permanent collection, usually a museum.

During a biological survey of South Australia’s Eyre Peninsula in 2003, Dr Catherine Kemper, Senior Research Scientist, Mammals, observed some unusual juvenile dunnarts. The dunnarts, a type of small carnivorous marsupial, had a slightly shorter tail and greyer underparts compared to the common species in the region as well as a buff-coloured patch on top of the nose.

Dr Kemper collected specimens of the dunnarts and assembled an interdisciplinary team to identify the species. The team comprised Graham Medlinan Honorary Research Associate and the Museum’s subfossil expert , Mark Adams and Steve Cooper from the Museum's Evolutionary Biology Unit and Jeremy Austin from the University of Adelaide's Australian Centre for Ancient DNA.

Using the Museum’s collection, the newly collected voucher specimens and a combination of morphological and genetic methods, the team identified the specimens as grey-bellied dunnarts (Sminthopsis griseoventer)  a species not previously recorded in South Australia. This led to a comprehensive reassessment of the taxonomic status and distribution of the species.

Subfossils in the collection from mainland South Australia were reassessed. Grey-bellied dunnarts were found from six sites on Yorke and Eyre Peninsula and from a site in the far west of the State. The fact that the researchers were able to capture only juvenile dunnarts turned out to be a lucky coincidence. One of the important features to distinguish dunnart species is the presence or absence of a small cusp on the deciduous premolar, a tooth that is shed at about four months old. Subfossil skulls could also be identified using this characteristic.

The research demonstrated that grey-bellied dunnarts were present in South Australia pre- and post-European settlement. Prior to European settlement they were much more widespread. Allozyme electrophoresis provided no evidence of genetic heterogeneity across their geographic range and indicated that gene flow across the Nullarbor was relatively recent. Mitochondrial DNA analysis confirmed the presence of at least four distinct species of Sminthopsis in specimens collected from Eyre Peninsula. A dunnart skin collected in a 1970s survey that had been misidentified was also correctly identified as a grey-bellied dunnart.

The collection of voucher specimens and tissues for morphological and genetic analysis is essential to identifying cryptic species like the grey-bellied dunnart. Biological surveys and environmental impact assessments that fail to collect voucher specimens may considerably under-estimate species diversity, the conservation value of a region and the impact of human activity.
