Systematics of the Freshwater Crayfish Genus Cherax Erichson (Decapoda: Parastacidae) in South-Western Australia: Electrophoretic, Morphological and Habitat Variation

Abstract

A detailed study of electrophoretic, morphological and habitat variation amongst species of Cherax in south-western Australia supported the recognition of only five of the eight species currently recognised and revealed that morphological and habitat variation within these crayfish is more extensive and complicated than was previously realised. Within several species morphological and habitat variation was found to be as great as that between species. Furthermore, a major component of the morphological variability, both within and between species, was found to be associated with habitat variation. Three of the five species of Cherax recognised in this study correspond to the consistently recognised and widespread species, C. preissii Erichson, C. quinquecarinatus (Gray) and C. tenuimanus Smith. The two other species are C. crassimantus Riek and C. glaber Riek which have restricted distributions in the extreme south-west of Western Australia. The species C. glabrimanus Riek and C. neocarinatus Riek could not be distinguished from C. quinquecarinatus, nor could C. plebejus (Hess) be distinguished from C. preissii. On a general level, the results of this study question the value of morphological information in systematic studies of freshwater crayfish. Morphologically based taxonomic studies of freshwater crayfish need to be interpreted with caution because, firstly, taxonomic characters may be far more variable than realised; secondly, morphological and habitat differences cannot necessarily be equated with specific distinctions; and thirdly, genetically distinct species that occupy similar habitats need not be morphologically distinct.

Genetic diversity among red swamp crayfish (Procambarus clarkii) populations in the middle and lower reaches of the Yangtze River based on AFLP markers

“…The second hypothesis is that this genetic pattern within and between populations can be accounted for by a period of population expansion and migration or gene flow followed by contraction, isolation, and fragmentation of populations, which leads to genetic divergence mainly under the process of genetic drift and resulted in fixation of the alternative variants in a stochastic manner. Similar patterns of genetic differentiation have been described in crayfish species using allozyme studies (Austin and Knott, 1996).…”

“…Gouin et al (2001) have maintained that human transplantation has caused genetic differentiation in the endangered freshwater crayfish. The impact of habitat variation on genetic differentiation has been illustrated in several animals, particularly crayfish (Austin and Knott, 1996). In our study, the pattern of genetic differentiation among 6 populations could be explained by 2 hypotheses.…”

Two new freshwater crayfishes (Decapoda: Parastacidae) from Whitsunday Island, The Coral Sea, Australia

“…Named for Christopher M. Austin, whose research on the genus Cherax (e.g., Austin, 1986Austin, , 1996Austin & Knott, 1996) has contributed enormously to our current understanding of this large and culturally significant group of crayfish.…”

A multivariate approach for developing a dichotomous key for identification and differentiation of Puntius (Osteichthyes: Cyprinidae) species in Sri Lanka

“…Combination with the diagnostic morphological characters permitted full separation of all species. Length ratios were employed to remove individual size effects 37 , and in combination with the meristic characters distinguished all species and so were incorporated in the key (Table 7). …”