Genetic variation in some populations of the golden-striped salamander, Chioglossa lusitanica (Amphibia: Urodela), in Portugal

Genetic exchange across a hybrid zone within the Iberian endemic golden-striped salamander, Chioglossa lusitanica

The study of hybrid zones resulting from Pleistocene vicariance is central in examining the potential of genetically diverged evolutionary units either to introgress and merge or to proceed with further isolation. The hybrid zone between two mitochondrial lineages of Chioglossa lusitanica is located near the Mondego River in Central Portugal. We used mitochondrial and nuclear diagnostic markers to conduct a formal statistical analysis of the Chioglossa hybrid zone in the context of tension zone theory. Key results are: (i) cline centres are not coincident for all markers, with average widths of ca. 2-15 km; (ii) heterozygote deficit was not observed across loci near the transect centre; (iii) associations of parental allele combinations ('linkage disequilibrium'R) were not detected either across loci or across the transect. These observations suggest that the Chioglossa hybrid zone is not a tension zone with strong selection against hybrids but instead one shaped mostly by neutral mixing. The patterns uncovered suggest a complex history of populations over a small scale that may be common in southern Pleistocene refugia.

Using the volumetric indices of telencephalic structures to distinguish Salamandridae and Plethodontidae: comparison of three statistical methods

The aim of this study was to establish whether appropriate statistical analysis of 16 volumetric indices corresponding to 16 structures making up the entire telencephalon of Urodela could distinguish between two families, Salamandridae and Plethodontidae. We compared the efficiency of three statistical methods (stepwise discriminant analysis, artificial neural networks, correspondence factor analysis) and the information they provide. All three methods found the same species difficult to classify. However, only correspondence factor analysis could suggest explanations for "misclassifications" as it superimposes the two sets of variables, (sub)species and anatomical variables, thus revealing the correlations between them. The bulbus olfactorius accessorius and the caudal mitral cell layer of the bulbus olfactorius principalis were the most discriminatory structures in separating Salamandridae and Plethodontidae. The correspondence factor analysis mapped species very much in line with accepted taxonomy and highlighted several current controversies [e.g. positioning of certain newts (T. marmoratus, T. vulgaris, T. alpestris), of Salamandrina terdigitata, and of members of the genus Euproctus]. Mapping of Plethodontidae was less clear-cut than that of Salamandridae with more overlap among genera but was quite consistent with knowledge of brain structure complexification. We conclude that relationships derived from analyses of telencephalic structures provide valuable information that might help resolve ambiguities; we have coined the term "neurotaxonomy" for this approach.

Genetic subdivision, glacial refugia and postglacial recolonization in the golden-striped salamander, Chioglossa lusitanica (Amphibia: urodela)

The golden-striped salamander (Chioglossa lusitanica) is an ecologically specialized species, endemic to north-western Iberia. Patterns of genetic variation were assessed at seven polymorphic enzyme loci and one mitochondrial DNA (mtDNA) marker (cytochrome b) in 17 populations across its range. Estimates of enzyme genetic diversity revealed a high degree of genetic subdivision (FST = 0.68), mainly attributable to the existence of two groups of populations. The groups were located, respectively, north and south of the Mondego River, indicating that this river coincided with a major historical barrier to gene flow. A significant decrease in genetic variability from the Mondego northwards was associated with the Douro and Minho rivers. mtDNA sequence variation revealed a congruent pattern of two haplotype groups (d = 2.2%), with a geographical distribution resembling that of allozymes. The pattern and depth of genetic variation is consistent with the following hypotheses: (i) subdivision of an ancestral range of the species prior to the middle Pleistocene; (ii) secondary contact between populations representing historical refugia; (iii) relatively recent range expansion giving rise to the northern part of the species range; and (iv) loss of genetic variation through founder effects during range expansion across major rivers.