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Carapace dentition patterns, morphometrics and allozyme differentiation amongst two toothed freshwater crab species (Potamonautes warreni and P. unispinus) (Decapoda: Brachyura: Potamonautidae) from river systems in South Africa

Published online by Cambridge University Press:  10 October 2001

Savel R. Daniels ,
Barbara A. Stewart ,
Tyrone M. Ridgway  and
Wayne Florence
Savel R. Daniels
Affiliation:
Molecular Zoology Laboratory, Department of Zoology, University of Stellenbosch, Private Bag X 1, Matieland, 7602, South Africa
Barbara A. Stewart
Affiliation:
Molecular Zoology Laboratory, Department of Zoology, University of Stellenbosch, Private Bag X 1, Matieland, 7602, South Africa Centre for Marine Studies, University of Queensland, St Lucia, Queensland 4072, Australia
Tyrone M. Ridgway
Affiliation:
Centre for Marine Studies, University of Queensland, St Lucia, Queensland 4072, Australia
Wayne Florence
Affiliation:
Zoology Department, University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa
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Abstract

The taxonomic relationship between two toothed South African river crabs, Potamonautes warreni and P. unispinus, is unclear. The problem stems from the widespread variation in carapace dentition patterns amongst P. warreni individuals over its biogeographic range, where single toothed individuals may appear similar in carapace morphology to P. unispinus. Ten populations of P. warreni and 18 populations of P. unispinus were collected and the morphometric and genetic differentiation between the two taxa quantified. Patterns of morphometric and genetic variation were examined using multivariate statistics and protein gel electrophoresis, respectively. Principal component analyses of carapace characters showed that the two species are morphologically indistinguishable. However, discriminate functions analyses and additional statistical results corroborate the morphological distinction between the two taxa. Allozyme electrophoresis of 17 protein coding loci, indicated a close genetic similarity between the two species (I = 0.92). A fixed allelic difference at one locus (LT-2) and extensive genetic variability at another locus (PGM-1) indicate that two gene pools are present and that the two taxa are genetically isolated. Intraspecific genetic I values for both species were >0.97 and indicated no apparent genetic structuring on a micro or macro-geographic scale. The variation in carapace dentition among P. warreni populations possesses no genetic basis and may possibly be the product of ecogenesis. The value of dentition patterns in the systematics of river crabs is discussed. Dentition patterns among river crab species appear to be conserved and reliable as species specific diagnostic markers, but should ideally be used in combination with other morphological data sets and genetic evidence.

Keywords

Potamonautescarapace dentitionmorphometricsallozymessystematicsfreshwater crabs
Type
Research Article
Information
Journal of Zoology , Volume 255 , Issue 3 , November 2001 , pp. 389 - 404
Copyright
© 2001 The Zoological Society of London

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