Genetic-Variation in Yabbies, Cherax-Destructor and C-Albidus (Crustacea, Decapoda, Parastacidae), Indicates the Presence of a Single, Highly Sub-Structured Species

Abstract

The high degree of morphological variability exhibited by yabbies (Cherax destructor Clark and C. albidus Clark) prompted this investigation of genetic variation, specifically addressing the taxonomy and population structure of these freshwater crayfish. Yabbies from 14 localities in South Australia and Victoria were classified morphologically and examined electrophoretically at 35 gene loci. Morphometric analysis confirmed the existence of two morphotypes with allopatric distributions. Genetic divergence between morphotypes was relatively low (average fixed differences = 4.72%, average Nei D = 0.085) compared with known interspecific levels-both generally and within the genus Cherax-and levels of divergence between populations within the morphotypes. Subspecific status for albidus is consequently advocated. This species shows evidence of a high degree of genetic fragmentation, with significant heterogeneity occurring at two or more loci between even the closest localities. Gene flow appears to be severely restricted even within drainage basins and a 'stepping-stone' model of population structure may be appropriate. This high degree of genetic fragmentation may explain the variable morphology of this species although phenotypic plasticity could also play a role. Genetic variation was chaotically distributed (the only consistent geographic pattern of divergence corresponding to the albidus morphotype), probably reflecting numerous translocations of this species. The results highlight the need for taxonomy and management to be based on genetic as well as morphological subdivisions.