Substantial allozyme diversity in the freshwater crayfish Parastacoides tasmanicus supports extensive cryptic speciation

Abstract

Allozyme electrophoretic studies on the freshwater crayfish genus Parastacoides Clark suggest the presence of several cryptic species within this morphologically conservative taxon. Two independent allozyme studies were undertaken to assess the validity of the current taxonomy of this monotypic genus. An initial study examined 42 individuals from 10 sample sets for allozyme variation at 22 putative loci, and a subsequent study surveyed an additional 72 specimens from 20 sample sets at 16 putative loci. Both studies revealed the same general outcomes, namely: (1) several instances of sympatric species diagnosable at multiple allozyme loci; (2) numerous examples of putative allopatric species with significant levels of genetic divergence (25–81% fixed difference, 0.30–1.67 Nei distance) well beyond those found between conspecific populations of any parastacid; (3) broad genetic affinities among putative species are inconsistent with currently recognised morphotypes; and (4) low levels of within-population genetic variability, typical of parastacids. Although it is not possible to determine how many species are represented on the basis of these two preliminary studies, the allozyme data nevertheless indicate that an absolute minimum of 11 species and perhaps as many as 19 species are likely to be present in the genus. They indicate the need for a thorough taxonomic revision of the genus using both molecular and morphological data.