Genetic subdivision, glacial refugia and postglacial recolonization in thegolden-striped salamander, Chioglossa lusitanica (Amphibia : Urodela)

The golden-striped salamander (Chioglossa lusitanica) is an ecologically sp ecialized species, endemic to north-western Iberia. Patterns of genetic var iation were assessed at seven polymorphic enzyme loci and one mitochondrial DNA (mtDNA) marker (cytochrome b) in 17 populations across its range. Esti mates of enzyme genetic diversity revealed a high degree of genetic subdivi sion (F-ST = 0.68), mainly attributable to the existence of two groups of p opulations. The groups were located, respectively, north and south of the M ondego River, indicating that this river coincided with a major historical barrier to gene flow. A significant decrease in genetic variability from th e 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 hy potheses: (i) subdivision of an ancestral range of the species prior to the middle Pleistocene; (ii) secondary contact between populations representin g historical refugia; (iii) relatively recent range expansion giving rise t o the northern part of the species range; and (iv) loss of genetic variatio n through founder effects during range expansion across major rivers.