Geographic variation and taxonomy of crested newts (Triturus cristatus superspecies): morphological and mitochondrial DNA data

Within the newt genus Triturus, the large-bodied species in the T. cristatu s(crested newt) superspecies show an unusual degree of variation in relativ e trunk length as a result of among-taxon variation in interlimb vertebral count. Here we examine the systematic value of this feature as assessed by both exterior measurement (Wolterstorff Index) and direct radiographic coun t of rib-bearing vertebrae, with particular reference to a number of confou nding factors (sex differences, hybridisation, geographic variation, allome try, preservation effects). Using our mtDNA haplotype data, which are large ly concordant with geographic distribution of species, we find that direct count of the rib-bearing vertebrae performs more reliably (14% misclassific ation) than external measurement (31% misclassification) as a species ident ifier. We therefore recommend this feature as a taxonomic tool, although (l ike external measurement) it breaks down near hybrid zones. To account for the observed biogeographical pattern and phenotype - genotype discrepancies , a scenario is presented that combines the movement of the contact zone be tween taxa with asymmetric hybridisation. This scenario applies to species interactions in eastern Yugoslavia and western France.