Abstract
Background:
Fluctuating climatic changes during the Pleistocene period played a significant role in shaping the population genetic structure of many species in northern and southern Australia.

Aim:
This study investigated the population structure and evolutionary history of an important disease vector, the Australian saltmarsh mosquito (Aedes vigilax), across the continent.

Methods:
Sequences of a 433-bp region of the mitochondrial cytochrome oxidase I gene were analyzed from a total of 318 individuals of this vector.

Results:
Bayesian analysis revealed two distinctly divergent clades, with an estimated divergence time of approximately 0.9 million years ago. Haplotype mismatch distribution and Fu's Fs tests inferred a recent demographic expansion during the late Pleistocene (6,000–13,000 years ago). Analysis of molecular variance showed significant genetic structuring, although gene flow remains high.

Conclusion:
We suggest that historical arid barriers caused genetic divergence, which was followed by range expansions in the east and west, with a greater spread from west to east. This supports the hypothesis that two cryptic lineages may exist. Population genetic data indicate substantial dispersal abilities in Ae. vigilax, suggesting an important role for this species in the spread of Ross River virus across the Australian continent.

Key words: Aedes vigilax; Arboviral vector; Genetic variation; Population structure; Australia.