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The golden-striped salamander, Chioglossa lusitanica, is a streamside species distributed in the northwest of the Iberian Peninsula. We gathered cytochrome b mitochondrial DNA sequence data from samples across the species range and used nested clade distance analysis to assess evolutionary processes explaining the geographical distribution of mtDNA diversity in Chioglossa lusitanica. A significant association was observed between genetic structure and geography. The geographical patterns were explained by past fragmentation and restricted gene flow. Inferences were concordant

Depletion of polymorphism at major histocompatibility complex (MHC) genes has been hypothesized to limit the ability of populations to respond to emerging pathogens, thus putting their survival at risk. As pathogens contribute substantially to the global amphibian decline, assessing patterns of MHC variation is important in devising conservation strategies. Here, we directly compare levels of MHC class II and neutral variation between multiple populations of the great crested newt (Triturus cristatus) from refugial (REF: Romania) and postglacial expansion (PGE: Germany, Poland and UK) areas. REF populations harboured high levels of adaptive variation (24 expressed alleles), exhibiting clear signatures of historical positive selection, which points to the overall importance of MHC class II variation in this species. On the other hand, PGE populations were extremely depauperate (two alleles) but nevertheless have survived for c. 10,000 years, since the postglacial expansion. Variation in putative MHC class II pseudogenes, microsatellites and allozymes also showed a significant southern richness-northern purity pattern. The populations in the postglacial expansion area thus provide the clearest example to date of the long-term survival of populations in which MHC variation, historically under positive selection, has been depleted.

Estimates of the effective number of breeding adults were derived for three semi-isolated populations of the common toad Bufo bufo based on temporal (i.e. adult-progeny) variance in allele frequency for three highly polymorphic minisatellite loci. Estimates of spatial variance in allele frequency among populations and of age-specific measures of genetic variability are also described. Each population was characterized by a low effective adult breeding number (Nb) based on a large age-specific variance in minisatellite allele frequency. Estimates of Nb (range 21-46 for population means across three loci) were approximately 55-230-fold lower than estimates of total adult census size. The implications of low effective breeding numbers for long-term maintenance of genetic variability and population viability are discussed relative to the species' reproductive ecology, current land-use practices, and present and historical habitat modification and loss. The utility of indirect measures of population parameters such as Nb and Ne based on time-series data of minisatellite allele frequencies is discussed relative to similar measures estimated from commonly used genetic markers such as protein allozymes.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Applied Ecology. Summary 1. We have used a stochastic population model with immigration to calculate extinction rates for two amphibian species: the common toad, Bufo bufo, and the crested newt, Triturus cristatus. 2. Population models for amphibians are difficult to parameterize. It was not possible to measure all the relevant parameters for the model. The other parameters were obtained from other studies or estimated on the basis of similar species. 3. Contour maps for persistence were generated using the model. The persistence of populations associated with a pond is affected both by the pond's internal dynamics and its proximity to a source pond. On a 20-generation time scale, toad ponds that were initially occupied were relatively unaffected by the proximity of a source. Persistence was almost certain (> 95%) when the average carrying capacity of a pond was greater than 30 adult females. Initially unoccupied toad-ponds were equally likely to persist if they lay within 4 km of a source and could support more than 50 adult females. Initially occupied newt ponds were likely to persist if they supported more than 40 females or lay within 0 5 km of a typical source pond. Initially unoccupied newt ponds were mainly dependent upon immigration rates. Very small ponds (Nk < 10) could persist if they lay within 0 75 km of a source pond, while large ponds (Nk >> 10) only needed to be within 1 5 km of a source pond. 4. This model allows us to use the data available, to make predictions about the criteria which must be met by a landscape to ensure the survival of amphibian populations. It offers the possibility of better predictions when the data is refined. The model also suggests directions for further research such as the statistical study of environmental variation, the nature of minimum viable populations for toads and the statistics of long-range dispersal.

All the currently available data with regard to morphology, palaeontology, biochemical genetics, reproductive interactions and behaviour have been collated and analysed with combinations of phenetic and numerical phylogenetic methods, and integrated into a consensus evolutionary tree for European newts of the genus Triturus.

Gene flow and drift shape the distribution of neutral genetic diversity in metapopulations, but their local rates are difficult to quantify. To identify gene flow between demes as distinct from individual migration, we present a modified Bayesian method to genetically test for descendants between an immigrant and a resident in a nonmigratory life stage. Applied to a metapopulation of pond‐breeding European newts (Triturus cristatus, T. marmoratus) in western France, the evidence for gene flow was usually asymmetric and, for demes of known census size (N), translated into maximally seven reproducing immigrants. Temporal sampling also enabled the joint estimation of the effective demic population size (Ne) and the immigration rate m (including nonreproductive individuals). Ne ranged between 4.1 and 19.3 individuals, Ne/N ranged between 0.05 and 0.65 and always decreased with N; m was estimated as 0.19–0.63, and was possibly biased upwards. We discuss how genotypic data can reveal fine‐scale demographic processes with important microevolutionary implications.