The monophyletic origin of freshwater crayfish estimated from nuclear and mitochondrial DNA sequences

Despite their widespread use as model organisms, the phylogenetic status of the around 520 species of freshwater crayfish is still in doubt. One hypot hesis suggests two distinct origins of freshwater crayfish as indicated by their geographical distribution, with two centres of origin near the two pr esent centres of diversity; one in south-eastern United States and the othe r in Victoria, Australia. An alternative theory proposes a single (monophyl etic) origin of freshwater crayfish. Here we use over 3000 nucleotides from three different gene regions in estimating phylogenetic relationships amon g freshwater crayfish and related Crustacea. We show clear evidence for mon ophyly of freshwater crayfish and for the sister-group relationship between crayfish and clawed lobsters. Monophyly of the superfamilies Astacoidea an d Parastacoidea is also supported. However, the monophyly of the family Cam baridae is questioned with the genus Cambaroides being associated with the Astacidae.