A novel genus and cryptic species harboured within the monotypic freshwater crayfish genus Riek, 1951 (Decapoda: Parastacidae).

Identifying species groups is an important yet difficult task, with there being no single accepted definition as to what constitutes a species, nor a set of criteria by which they should be delineated. Employing the General Lineage Concept somewhat circumvents these issues, as this concept allows multiple concordant lines of evidence to be used as support for species delimitation, where a species is defined as any independently evolving lineage. Genetically diverse groups have previously been identified within the monotypic parastacid genus Riek, 1951, but no further investigation of this diversity has previously been undertaken. Analysis of two mitochondrial DNA gene regions has previously identified two highly divergent groups within this taxon, representing populations from Queensland (Qld) and New South Wales (NSW), respectively. Additional testing within this study of both mitochondrial and nuclear DNA through species discovery analyses identified genetically diverse groups within these regions, which were further supported by lineage validation methods. The degree of genetic differentiation between Qld and NSW populations supports the recognition of two genera; with Qld retaining the original genus name , and NSW designated as until a formal description is completed. Concordance between the species discovery and lineage validation methods supports the presence of six species within and two within . The recognition of additional species removes the monotypy of the genus, and the methods used can improve species identification within groups of organisms with taxonomic problems and cryptic diversity.