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Trevor J. C. Beebee - One of the best experts on this subject based on the ideXlab platform.
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drift rather than selection dominates mhc class ii allelic diversity patterns at the biogeographical range scale in Natterjack Toads bufo calamita
PLOS ONE, 2014Co-Authors: Inga Zeisset, Trevor J. C. BeebeeAbstract:Study of major histocompatibility complex (MHC) loci has gained great popularity in recent years, partly due to their function in protecting vertebrates from infections. This is of particular interest in amphibians on account of major threats many species face from emergent diseases such as chytridiomycosis. In this study we compare levels of diversity in an expressed MHC class II locus with neutral genetic diversity at microsatellite loci in Natterjack Toad (Bufo (Epidalea) calamita) populations across the whole of the species’ biogeographical range. Variation at both classes of loci was high in the glacial refugium areas (REF) and much lower in postglacial expansion areas (PGE), especially in range edge populations. Although there was clear evidence that the MHC locus was influenced by positive selection in the past, congruence with the neutral markers suggested that historical demographic events were the main force shaping MHC variation in the PGE area. Both neutral and adaptive genetic variation declined with distance from glacial refugia. Nevertheless, there were also some indications from differential isolation by distance and allele abundance patterns that weak effects of selection have been superimposed on the main drift effect in the PGE zone.
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Natterjack Toad distribution and sampling sites for microsatellite and MHC analyses.
2014Co-Authors: Inga Zeisset, Trevor J. C. BeebeeAbstract:Dark shading indicates Natterjack Toad distribution in Europe. Black circles indicate sites for which both MHC and microsatellite data was collected, white circles indicate MHC data only and grey circles microsatellite data only. Sampling sites (area or nearest town) were: 1. Algarve, Portugal; 2. Seville, Spain; 3. Doñana, Spain; 4. Almeria, Spain; 5. Leon, Spain; 6. Bordeaux, France; 7. Carmargue, France; 8 and 9 near Zurich, Switzerland; 10. Carnac, France; 11. Penmarch, France; 12. Cherbourg, France; 13. Kerry, Ireland; 14. Birkdale, UK; 15. Winterton, UK; 16. Texel, Netherlands; 17. Halle, Germany; 18. Bukowno, Poland; 19. Bielowieza, Poland; 20. Zealand, Denmark; 21. Uddevalla, Sweden; 22. Parnu, Estonia. The dashed line indicates the approximate division between the glacial refugia (REF) and postglacial expansion (PGE) areas. Map modified from d-maps.com.
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larval fitness and immunogenetic diversity in chytrid infected and uninfected Natterjack Toad bufo calamita populations
Conservation Genetics, 2011Co-Authors: S May, Inga Zeisset, Trevor J. C. BeebeeAbstract:Chytrid fungus Batrachochytrium dendrobatidis (Bd), an emerging disease, has been decimating amphibian populations around the world for several decades. We quantified aspects of larval fitness, adaptive (major histocompatibility complex) diversity and neutral (microsatellite) diversity in Natterjack Toad (Bufo calamita) populations in two regions of north-west England. Toads in region one had no evidence of chytrid infection, whereas in region two there was a substantial prevalence of Bd. Larval fitness (growth rate, time to metamorphosis and survival) of B. calamita did not differ between the regions. Genetic diversity at microsatellite loci was much higher in the infected than in the uninfected region, but the converse was true of MHC diversity indicating that genetic drift was unlikely to explain the differences in MHC between the regions. Furthermore, MHC allele frequencies varied significantly between Bd-infected and uninfected populations. Microsatellite diversity was not a robust indicator of larval fitness in these Toad populations while MHC genotype frequencies varied in a way that was consistent with directional selection in response to pathogen prevalence. The acquired immune defences may therefore play an important role in determining the susceptibility of amphibian species to chytridiomycosis.
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a comparison of single sample effective size estimators using empirical Toad bufo calamita population data genetic compensation and population size genetic diversity correlations
Molecular Ecology, 2009Co-Authors: Trevor J. C. BeebeeAbstract:The accuracy and precision of four single-sample estimators of effective population size, Ne (heterozygote excess, linkage disequilibrium, Bayesian partial likelihood and sibship analysis) were compared using empirical data (microsatellite genotypes) from multiple Natterjack Toad (Bufo calamita) populations in Britain (n = 16) and elsewhere in Europe (n = 10). Census size data were available for the British populations. Because Toads have overlapping generations, all of these methods estimated the number of effective breeders Nb rather than Ne. The heterozygote excess method only provided results, without confidence limits, for nine of the British populations. Linkage disequilibrium gave estimates for 10 British populations, but only six had finite confidence limits. The Bayesian and sibship methods both produced estimates with finite confidence limits for all the populations. Although the Bayesian method was the most precise, on most criteria (insensitivity to locus number, correlation with other effective and census size estimates and correlation with genetic diversity) the sibship method performed best. The results also provided evidence of genetic compensation in Natterjack Toads, and highlighted how the relationship between effective size and genetic diversity can vary as a function of geographical scale.
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characterisation of major histocompatibility complex class ii alleles in the Natterjack Toad bufo calamita
Conservation Genetics Resources, 2009Co-Authors: S May, Trevor J. C. BeebeeAbstract:Major histocompatibility complex (MHC) class II genes play a major role in the vertebrate immune response, and are useful indicators of adaptive variation in wild populations. We developed PCR primers for part (114 bp excluding primers, coding for 38 amino acids) of the second exon of two expressed MHC class II genes (designated A and B) in the Natterjack Toad Bufo calamita. We detected five alleles in 200 individuals from range-edge populations in Britain, two of which we ascribed to locus A and three to locus B. Seven out of 10 variable amino acid sites were associated with antigen binding. In a discrete study population we detected a significant excess of non-synonymous substitutions at antigen binding sites, and a heterozygote excess, at locus A indicating that this gene is under positive selection. However, there were no significant excesses of non-synonymous substitutions or heterozygotes at locus B.
Miguel Tejedo - One of the best experts on this subject based on the ideXlab platform.
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predation by an exotic crayfish procambarus clarkii on Natterjack Toad bufo calamita embryos its role on the exclusion of this amphibian from its breeding ponds
Copeia, 2006Co-Authors: Maria Joao Cruz, Miguel Tejedo, Sandra Pascoal, Rui RebeloAbstract:Abstract Procambarus clarkii, an American crayfish, was introduced in the SW Iberian Peninsula three decades ago. This region has no native crayfishes; therefore, P. clarkii constitutes a potential threat for the embryos and larvae of amphibians, which may lack evolved defenses against it. We assessed the effects of this crayfish on the Natterjack Toad, Bufo calamita, using two complementary approaches. First, we studied the effect of crayfish presence on B. calamita breeding habitat use in temporary ponds of Donana Natural Park (southwestern Spain). We surveyed 31 temporary ponds for the presence of P. clarkii and B. calamita eggs and tadpoles, and we conducted a logistic regression to determine if crayfish were significantly associated with Natterjack Toad distribution after habitat variables were taken into account. Second, we experimentally evaluated the impact of P. clarkii on B. calamita embryos in natural ponds with a two × two factorial experiment, using two ponds (one with and one without crayfis...
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adaptation or exaptation an experimental test of hypotheses on the origin of salinity tolerance in bufo calamita
Journal of Evolutionary Biology, 2005Co-Authors: Ivan Gomezmestre, Miguel TejedoAbstract:The Natterjack Toad (Bufo calamita) shows variation in embryonic and larval salinity tolerance across populations in southern Spain. However, its aquatic/ terrestrial biphasic life cycle, together with remarkable differences in salinity tolerance between Spanish and UK freshwater populations suggest an alternative hypothesis to local adaptation. Drought resistance during the terrestrial phase and salinity tolerance during the aquatic phase are both related to osmotic stress tolerance, and if there were an association between them, one could have evolved as an exaptation from the other. To test such an association, we reared B. calamita juveniles from three populations known to differ genetically in their salinity tolerance, under either dry or humid conditions. Drought decreased growth rate, enhanced burying behaviour, and decreased foraging activity and efficiency. No significant population · treatment interaction was found for any variable, i.e. populations were equally affected by drought. These results do not support the hypothesis of a genetic association between salinity and drought tolerance.
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contrasting patterns of quantitative and neutral genetic variation in locally adapted populations of the Natterjack Toad bufo calamita
Evolution, 2004Co-Authors: Ivan Gomezmestre, Miguel TejedoAbstract:The relative importance of natural selection and genetic drift in determining patterns of phenotypic diversity observed in nature is still unclear. The Natterjack Toad (Bufo calamita) is one of a few amphibian species capable of breeding in saline ponds, even though water salinity represents a considerable stress for them. Results from two common-garden experiments showed a pattern of geographic variation in embryonic salinity tolerance among populations from either fresh or brackish environments, consistent with the hypothesis of local adaptation. Full-sib analysis showed increased variation in survival among sibships within population for all populations as osmotic stress was increased (broad-sense heritability increased as salinity raised). Nevertheless, Toads native to the brackish water environment had the highest overall survival under brackish conditions. Levels of population genetic differentiation for salinity tolerance were higher than those of neutral genetic differentiation, the latter obtained through the analysis of eight microsatellite loci. Microsatellite markers also revealed little population differentiation, lack of an isolation-by-distance pattern, and moderate gene flow connecting the populations. Therefore, environmental stress tolerance appears to have evolved in absence of geographic isolation, and consequently we reject the null hypothesis of neutral differentiation.
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contrasting patterns of quantitative and neutral genetic variation in locally adapted populations of the Natterjack Toad
2004Co-Authors: Ivan Gomezmestre, Miguel Tejedo, Pabellon Del PertiAbstract:The relative importance of natural selection and genetic drift in determining patterns of phenotypic diversity observed in nature is still unclear. The Natterjack Toad (Bufo calamita) is one of a few amphibian species capable of breeding in saline ponds, even though water salinity represents a considerable stress for them. Results from two common-garden experiments showed a pattern of geographic variation in embryonic salinity tolerance among pop- ulations from either fresh or brackish environments, consistent with the hypothesis of local adaptation. Full-sib analysis showed increased variation in survival among sibships within population for all populations as osmotic stress was increased (broad-sense heritability increased as salinity raised). Nevertheless, Toads native to the brackish water environment had the highest overall survival under brackish conditions. Levels of population genetic differentiation for salinity tolerance were higher than those of neutral genetic differentiation, the latter obtained through the analysis of eight microsatellite loci. Microsatellite markers also revealed little population differentiation, lack of an isolation- by-distance pattern, and moderate gene flow connecting the populations. Therefore, environmental stress tolerance appears to have evolved in absence of geographic isolation, and consequently we reject the null hypothesis of neutral differentiation.
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Absence of the trade-off between the size and number of offspring in the Natterjack Toad (Bufo calamita)
Oecologia, 1992Co-Authors: Miguel TejedoAbstract:A trade-off between size and number of offspring was not found for females of similar sizes of the Natterjack Toad ( Bufo calamita ). Moreover, for large females, clutches with higher number of eggs had larger eggs as well. This suggests that larger females produce more numerous and larger eggs because they potentially have more energy available for reproduction. Egg size diminished allometrically with clutch size. Egg size, however, did not increase offspring fitness. Therefore, this allometric decrease may be considered a consequence of phylogenetic constraints rather than a result of optimizing selection.
Jean-françois Arnaud - One of the best experts on this subject based on the ideXlab platform.
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When new human-modified habitats favour the expansion of an amphibian pioneer species: Evolutionary history of the Natterjack Toad (Bufo calamita) in a coal basin.
Molecular Ecology, 2017Co-Authors: Leslie Faucher, Laura Henocq, Cédric Vanappelghem, Stéphanie Rondel, Robin Quevillart, Sophie Gallina, Cécile Godé, Julie Jaquiéry, Jean-françois ArnaudAbstract:Human activities affect microevolutionary dynamics by inducing environmental changes. In particular, land cover conversion and loss of native habitats decrease genetic diversity and jeopardize the adaptive ability of populations. Nonetheless, new anthropogenic habitats can also promote the successful establishment of emblematic pioneer species. We investigated this issue by examining the population genetic features and evolutionary history of the Natterjack Toad (Bufo [Epidalea] calamita) in northern France, where populations can be found in native coastal habitats and coalfield habitats shaped by European industrial history, along with an additional set of European populations located outside this focal area. We predicted contrasting patterns of genetic structure, with newly settled coalfield populations departing from migration-drift equilibrium. As expected, coalfield populations showed a mosaic of genetically divergent populations with short-range patterns of gene flow, and native coastal populations indicated an equilibrium state with an isolation-by-distance pattern suggestive of postglacial range expansion. However, coalfield populations exhibited (i) high levels of genetic diversity, (ii) no evidence of local inbreeding or reduced effective population size and (iii) multiple maternal mitochondrial lineages, a genetic footprint depicting independent colonization events. Furthermore, approximate Bayesian computations suggested several evolutionary trajectories from ancient isolation in glacial refugia during the Pleistocene, with biogeographical signatures of recent expansion probably confounded by human-mediated mixing of different lineages. From an evolutionary and conservation perspective, this study highlights the ecological value of industrial areas, provided that ongoing regional gene flow is ensured within the existing lineage boundaries.
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development of nuclear microsatellite loci and mitochondrial single nucleotide polymorphisms for the Natterjack Toad bufo epidalea calamita bufonidae using next generation sequencing and competitive allele specific pcr kaspar
Journal of Heredity, 2016Co-Authors: Leslie Faucher, Cécile Godé, Jean-françois ArnaudAbstract:Amphibians are undergoing a major decline worldwide and the steady increase in the number of threatened species in this particular taxa highlights the need for conservation genetics studies using high-quality molecular markers. The Natterjack Toad, Bufo (Epidalea) calamita, is a vulnerable pioneering species confined to specialized habitats in Western Europe. To provide efficient and cost-effective genetic resources for conservation biologists, we developed and characterized 22 new nuclear microsatellite markers using next-generation sequencing. We also used sequence data acquired from Sanger sequencing to develop the first mitochondrial markers for KASPar assay genotyping. Genetic polymorphism was then analyzed for 95 Toads sampled from 5 populations in France. For polymorphic microsatellite loci, number of alleles and expected heterozygosity ranged from 2 to 14 and from 0.035 to 0.720, respectively. No significant departures from panmixia were observed (mean multilocus F IS = -0.015) and population differentiation was substantial (mean multilocus F ST = 0.222, P < 0.001). From a set of 18 mitochondrial SNPs located in the 16S and D-loop region, we further developed a fast and cost-effective SNP genotyping method based on competitive allele-specific PCR amplification (KASPar). The combination of allelic states for these mitochondrial DNA SNP markers yielded 10 different haplotypes, ranging from 2 to 5 within populations. Populations were highly differentiated (G ST = 0.407, P < 0.001). These new genetic resources will facilitate future parentage, population genetics and phylogeographical studies and will be useful for both evolutionary and conservation concerns, especially for the set-up of management strategies and the definition of distinct evolutionary significant units.
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Microsatellite and mtDNA genotypes for Bufo calamita
2016Co-Authors: Leslie Faucher, Cécile Godé, Jean-françois ArnaudAbstract:Population coordinates and microsatellite and mtDNA genotypes for five populations of the Natterjack Toad (Bufo calamita). Location : France
Jacob Hoglund - One of the best experts on this subject based on the ideXlab platform.
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low mhc variation in isolated island populations of the Natterjack Toad bufo calamita
Conservation Genetics, 2015Co-Authors: Jacob Hoglund, Bjorn Rogell, Asa Wengstrom, Yvonne MeyerluchtAbstract:We studied variation at the class II gene of the major histocompatibility complex (MHC) in Natterjack Toad populations (Bufo [Epidalea] calamita) on islands off the west coast of Sweden. These isolated populations have previously been shown to exhibit low levels of neutral genetic variation. On seven investigated islands we found only two different MHC alleles, indicating that the genetic variation at this locus is also low. The two alleles were found in all populations, although in one population there was only a single heterozygous individual. The Swedish Toads showed similar low levels of MHC variation as revealed by previously published data from populations in northern Europe. We did not find a correlation between MHC and neutral genetic variation (as determined by AFLP). However, our findings show that reduced genetic variation in the Swedish Natterjack Toads is not restricted to neutral markers, but is likewise reflected at the MHC.
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genetic structure in peripheral populations of the Natterjack Toad bufo calamita as revealed by aflp
Conservation Genetics, 2010Co-Authors: Bjorn Rogell, Hanna Thorngren, Stefan Palm, Anssi Laurila, Jacob HoglundAbstract:Decreased fitness due to loss of genetic variation is a well recognised issue in conservation biology. Along the Swedish west coast, the endangered Natterjack Toad (Bufo calamita) occurs on, for the species, highly unusual habitat of rocky islands. Although the Toads inhabit a restricted geographical area (maximum distance between the populations is 71 km), the fragmented nature of the landscape makes the genetic properties of the populations of conservation interest. However, lack of genetic variation found using conventional methods (microsatellites) has impeded genetic studies within these peripheral populations so far. In this study we assess population structure and genetic variation among seven of these fringe populations using 105 polymorphic Amplified Fragment Length Polymorphism (AFLP) loci. We found a well-defined population structure without evidence for isolation by distance, implying restricted gene flow between populations. Additionally, the populations differed in their amount of genetic variation, emphasizing the need to monitor genetically impoverished populations for possible declines mediated by inbreeding depression and reduced adaptive potential. Conservation implications for these unique populations are discussed in the light of our results.
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the interaction of multiple environmental stressors affects adaptation to a novel habitat in the Natterjack Toad bufo calamita
Journal of Evolutionary Biology, 2009Co-Authors: Bjorn Rogell, Anssi Laurila, Maarten P G Hofman, Martin Eklund, Jacob HoglundAbstract:The potential to adapt to novel environmental conditions is a key area of interest for evolutionary biology. However, the role of multiple selection pressures on adaptive responses has rarely been investigated in natural populations. In Sweden, the Natterjack Toad Bufo calamita inhabits two separate distribution areas, one in southernmost Sweden and one on the west coast. We characterized the larval habitat in terms of pond size and salinity in the two areas, and found that the western populations are more affected by both desiccation risk and pond salinity than the southern populations. In a common garden experiment manipulating salinity and temperature, we found that Toads from the west coast populations were locally adapted to shorter pond duration as indicated by their higher development and growth rates. However, despite being subjected to higher salinity stress in nature, west coast Toads had a poorer performance in saline treatments. We found that survival in the saline treatments in the west coast populations was positively affected by larger body mass and longer larval period. Furthermore, we found negative genetic correlations between body mass and growth rate and their plastic responses to salinity. These results implicate that the occurrence of multiple environmental stressors needs to be accounted for when assessing the adaptive potential of organisms and suggest that genetic correlations may play a role in constraining adaptation of natural populations.
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six polymorphic microsatellite loci in the Natterjack Toad bufo calamita
Molecular Ecology Notes, 2005Co-Authors: Bjorn Rogell, Niclas Gyllenstrand, Jacob HoglundAbstract:The Natterjack Toad, Bufo calamita, is a locally endangered anuran endemic to Europe. It has been used as a model organism in several ecological studies. When studying the genetic structure of marginalized populations of the species, there was a need to involve more loci in the study than those previously published. Here we present the development of six polymorphic microsatellite loci in the Natterjack. The loci will be used for studying population genetic structure and gene flow between populations.
Graham Rowe - One of the best experts on this subject based on the ideXlab platform.
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lusitania revisited a phylogeographic analysis of the Natterjack Toad bufo calamita across its entire biogeographical range
Molecular Phylogenetics and Evolution, 2006Co-Authors: Graham Rowe, James D Harris, Trevor J. C. BeebeeAbstract:Attempts to understand the current distributions of plants and animals require both historical and ecological information. Phylogeography has proved highly effective in elucidating historical events such as postglacial colonisations in north temperate zones. However, interesting questions still await resolution. Lusitanian distributions of fauna and flora in western Europe, for example, have puzzled biogeographers for more than 150 years. Lusitanian species have highly disjunct distributions in Ireland and in Iberia, often with few or no other populations inbetween. Despite much debate, no agreed explanation for Lusitanian distributions has yet emerged. We investigated the phylogeographic structure of one Lusitanian species, the Natterjack Toad Bufo calamita, using mitochondrial DNA control region sequences and allelic variation at eight microsatellite loci. Our results show that this amphibian must have survived in north European refugia, as well as in Iberia, during and since the last (Weichselian) glacial maximum around 20,000 years before present (BP). Subsequent local recolonisation after the Younger Dryas cooling around 11,000 years BP best explains the Lusitanian aspect of Natterjack Toad distribution.
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intraspecific competition disadvantages inbred Natterjack Toad bufo calamita genotypes over outbred ones in a shared pond environment
Journal of Animal Ecology, 2005Co-Authors: Graham Rowe, Trevor J. C. BeebeeAbstract:1. We carried out a replicated pond experiment to compare the viabilities of Natterjack Toad Bufo calamita embryos and larvae from inbred and outbred populations. Surviving genotypes were identified at the end of the experiment using fixed diagnostic alleles at a microsatellite locus. 2. Inbred larvae grew more slowly than outbred larvae and in mixed populations the survival of outbred larvae was three- to 10-fold higher than that of inbred larvae. 3. Larval mortality correlated with the abundance of dytiscid water beetles, and was therefore probably caused mainly by predation. The relatively higher rate of mortality of inbred larvae was in turn due probably to lower growth rates delaying achievement of a size refuge. 4. Intraspecific competition may help to purge inbred individuals in populations with mixed levels of inbreeding. The significance of inbreeding with relatively cryptic effects, such as reduction in amphibian larval growth rate, is discussed with respect to population viability.
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POPULATION ON THE VERGE OF A MUTATIONAL MELTDOWN? FITNESS COSTS OF GENETIC LOAD FOR AN AMPHIBIAN IN THE WILD
Evolution; international journal of organic evolution, 2003Co-Authors: Graham Rowe, Trevor J. C. BeebeeAbstract:The fitness costs of high genetic load in wild populations have rarely been assessed under natural conditions. Such costs are expected to be greatest in small, bottlenecked populations, including those occurring near range edges. Britain is at the northwesterly range limit of the Natterjack Toad Bufo calamita. We compared fitness attributes in two populations of this amphibian with very different recent histories. Key larval fitness attributes in B. calamita, notably growth rate and metamorph production, were substantially higher in the large outbreeding population (Ainsdale) than in the small and isolated one (Saltfleetby). These differences were manifest under seminatural conditions, when larvae were reared in mesh cages within breeding ponds at the site of the small population, and were exacerbated by high stress treatments. The results indicate that genetic load effects can be sufficiently severe enough to predispose extinction over relatively short time frames, as predicted by extinction vortex models.
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a microsatellite analysis of Natterjack Toad bufo calamita metapopulations
Oikos, 2000Co-Authors: Graham Rowe, Trevor J. C. Beebee, Terry BurkeAbstract:Although it is widely recognised that spatial subdivision of populations is common in nature, there is no consensus as to how metapopulation dynamics affect genetic diversity. We investigated the genetic differentiation of Natterjack Toads, Bufo calamita, in three regions of Britain where habitat continuity indicated the likely occurrence of extensive metapopulations. Our intention was to determine whether genetic analysis supported the existence of metapopulation structures, if so of what type, and to identify barriers to migration between subpopulations. Allele frequencies were determined across eight polymorphic microsatellite loci for a total of 24 Toad subpopulations at three separate sites. Genetic differentiation was assessed using five measures of genetic distance, notably FST, RST, Nei's standard distance Ds,Δμ2 and the Cavalli-Sforza chord distance Dc. B. calamita exhibited small but significant levels of genetic differentiation between subpopulations in all three study areas, and genetic and geographic distance correlations indicated isolation-by-distance effects in all three cases. The effects on correlation strengths of compensation for positive (sea, rivers, urban development) and negative (pond clusters) barriers to Toad migration between the subpopulations in each area were also determined. Dc, a measure which assumes that differentiation is caused by drift with negligible mutation effect, yielded the most plausible interpretation of metapopulation structures. Overall the patterns of genetic variation suggested the existence of a mixed metapopulation model for this species, with high levels of gene flow compatible with one version of the classical model but often supported by particularly stable subpopulations as in the mainland-island model.
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Regular ArticleMicrosatellite analysis of Natterjack Toad Bufo calamita Laurenti populations: consequences of dispersal from a Pleistocene refugium
Biological Journal of the Linnean Society, 2000Co-Authors: Trevor J. C. Beebee, Graham RoweAbstract:Populations of the amphibian Bufo calamita were sampled for genetic analysis in eleven areas distributed across its biogeographical range in Europe. Genetic diversity estimates across eight microsatellite loci showed a decline in polymorphism, numbers of alleles and heterozygosity as a function of distance from the presumed ice-age refugium in Iberia. Trials with a selection of tree-building algorithms indicated that UPGMA of Cavalli-Sforza chord distances (Dc) generated the tree topology most easily reconciled with other biogeographical information. Genetic distance measures were also calibrated against a postglacial event from which the separation of extant populations could be estimated in real time. Dcagain outperformed two other measures (Nei's standard distance,Ds , and δμ2) in producing realistic correlations with minimal variance. The genetic analysis was consistent with the hypothesis that B. calamita survived in a single refugium (Iberia) during the Pleistocene glaciation and indicated that it spread north and east from there during the last interstadial which commenced about 14 000 years before present (BP). Microsatellites should provide useful tools for biogeographical investigations of other species, especially with respect to patterns of population dispersal.