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
Sr. Daniels et al., 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, J ZOOL, 255, 2001, pp. 389-404
The taxonomic relationship between two toothed South African river crabs, P
otamonautes warreni and P. unispinus, is unclear. The problem stems from th
e widespread variation in carapace dentition patterns amongst P. warreni in
dividuals over its biogeographic range, where single toothed individuals ma
y appear similar in carapace morphology to P. unispinus. Ten populations of
P. warreni and 18 populations of P. unispinus were collected and the morph
ometric and genetic differentiation between the two taxa quantified. Patter
ns of morphometric and genetic variation were examined using multivariate s
tatistics and protein gel electrophoresis, respectively. Principal componen
t analyses of carapace characters showed that the two species are morpholog
ically indistinguishable. However, discriminate functions analyses and addi
tional statistical results corroborate the morphological distinction betwee
n the two taxa. Allozyme electrophoresis of 17 protein coding loci, indicat
ed a close genetic similarity between the two species (I = 0.92). A fixed a
llelic 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 mic
ro or macro-geographic scale. The variation in carapace dentition among P.
warreni populations possesses no genetic basis and may possibly toe the pro
duct of ecogenesis. The value of dentition patterns in the systematics of r
iver crabs is discussed. Dentition patterns among river crab species appear
to be conserved and reliable as species specific diagnostic markers, but s
hould ideally be used in combination with other morphological data sets and
genetic evidence.