title: The effects of selection, drift and genetic variation on life-history trait divergence among insular populations of natterjack toad, Bufo calamita.
abstract: Although loss of genetic variation is frequently assumed to be associated with loss of adaptive potential, only few studies have examined adaptation in populations with little genetic variation. On the Swedish west coast, the northern fringe populations of the natterjack toad Bufo calamita inhabit an atypical habitat consisting of offshore rock islands. There are strong among-population differences in the amount of neutral genetic variation, making this system suitable for studies on mechanisms of trait divergence along a gradient of within-population genetic variation. In this study, we examined the mechanisms of population divergence using Q(ST)-F(ST) comparisons and correlations between quantitative and neutral genetic variation. Our results suggest drift or weak stabilizing selection across the six populations included in this study, as indicated by low Q(ST)-F(ST) values, lack of significant population x temperature interactions and lack of significant differences among the islands in breeding pond size. The six populations included in this study differed in both neutral and quantitative genetic variation. Also, the correlations between neutral and quantitative genetic variation tended to be positive, however, the relatively small number of populations prevents any strong conclusions based on these correlations. Contrary to the majority of Q(ST)-F(ST) comparisons, our results suggest drift or weak stabilizing selection across the examined populations. Furthermore, the low heritability of fitness-related traits may limit evolutionary responses in some of the populations.
authors.affiliation: Population and Conservation Biology/Department of Ecology and Evolution, Evolutionary Biology Center, Uppsala University, Uppsala, Sweden. bjorn.rogell@ebc.uu.se
authors.forename: Björn
authors.initials: B
authors.lastname: Rogell
authors.forename: Martin
authors.initials: M
authors.lastname: Eklund
authors.forename: Hanna
authors.initials: H
authors.lastname: Thörngren
authors.forename: Anssi
authors.initials: A
authors.lastname: Laurila
authors.forename: Jacob
authors.initials: J
authors.lastname: Höglund
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000483:Alleles; D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D002025:Bufonidae / Q000235:genetics*; D005787:Gene Frequency; D040961:Genetic Drift; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D016014:Linear Models; D008957:Models, Genetic; D019655:Quantitative Trait, Heritable; D012641:Selection, Genetic; D013548:Sweden