BACKGROUND: Australian scorpions have received far less attention from 
researchers than their overseas counterparts. Here we provide the first insight 
into the molecular variation and evolutionary history of the endemic Australian 
scorpion Urodacus yaschenkoi. Also known as the inland robust scorpion, it is 
widely distributed throughout arid zones of the continent and is emerging as a 
model organism in biomedical research due to the chemical nature of its venom.
METHODS: We employed Bayesian Inference (BI) methods for the phylogenetic 
reconstructions and divergence dating among lineages, using unique haplotype 
sequences from two mitochondrial loci (COXI, 16S) and one nuclear locus (28S). 
We also implemented two DNA taxonomy approaches (GMYC and PTP/dPTP) to evaluate 
the presence of cryptic species. Linear Discriminant Analysis was used to test 
whether the linear combination of 21 variables (ratios of morphological 
measurements) can predict individual's membership to a putative species.
RESULTS: Genetic and morphological data suggest that U. yaschenkoi is a species 
complex. High statistical support for the monophyly of several divergent 
lineages was found both at the mitochondrial loci and at a nuclear locus. The 
extent of mitochondrial divergence between these lineages exceeds estimates of 
interspecific divergence reported for other scorpion groups. The GMYC model and 
the PTP/bPTP approach identified major lineages and several sub-lineages as 
putative species. Ratios of several traits that approximate body shape had a 
strong predictive power (83-100%) in discriminating two major molecular 
lineages. A time-calibrated phylogeny dates the early divergence at the onset of 
continental-wide aridification in late Miocene and Pliocene, with finer-scale 
phylogeographic patterns emerging during the Pleistocene. This structuring 
dynamics is congruent with the diversification history of other fauna of the 
Australian arid zones.
DISCUSSION: Our results indicate that the taxonomic status of U. yaschenkoi 
requires revision, and we provide recommendations for such future efforts. A 
complex evolutionary history and extensive diversity highlights the importance 
of conserving U. yaschenkoi populations from different Australian arid zones in 
order to preserve patterns of endemism and evolutionary potential.