Population genetic theory predicts that in small populations, random genetic drift will fix and accumulate slightly deleterious mutations, resulting in reduced reproductive output. This genetic load due to random drift (i.e., drift load) can increase the extinction risk of small populations. We studied the relationship between genetic variability (indicator of past population size) and reproduc...

Small and isolated island populations provide ideal systems to study the effects of limited population size, genetic drift and gene flow on genetic diversity. We assessed genetic diversity within and differentiation among 19 mockingbird populations on 15 Galápagos islands, covering all four endemic species, using 16 microsatellite loci. We tested for signs of drift and gene flow, and used histo...

The interaction of random gene drift and selection was studied by computer simulation for two quantitative traits, which were considered to approximate stature and skin color dlfferences in human populations. The expected effects of gene drift, fixation of alleles and reduction of genotypic and phenotypic variances, were found in the simulation. Stabilizing selection, which seems to be the type...

One hotly debated philosophical question in the analysis of evolutionary theory concerns whether or not evolution and the various factors which constitute it (selection, drift, mutation, and so on) may profitably be considered to be “forces” in the traditional, Newtonian sense. Several compelling arguments assert that the force picture is incoherent, due to the peculiar nature of genetic drift....

Both genetic drift and divergent selection are expected to be strong evolutionary forces driving population differentiation on edaphic habitat islands. However, the relative contribution of genetic drift and divergent selection to population divergence has rarely been tested simultaneously. In this study, restriction-site associated DNA-based population genomic analyses were applied to assess t...

Most mutations are deleterious and cause a reduction in population mean fitness known as the mutational load. In small populations, weakened selection against slightly-deleterious mutations results in an additional reduction in fitness: the drift load. Many studies have established that populations can evolve a reduced mutational load by evolving mutational robustness, but it is uncertain wheth...

Explanations for the genetic variation ubiquitous in natural populations are often classified by the population-genetic processes they emphasize: natural selection or mutation and genetic drift. Here we investigate models that incorporate all three processes in a spatially structured population, using what we call a construction approach, simulating finite populations under selection that are b...

number may not be closely related to the actual number of individuals, but the mathematical theories of genetic drift could still work. But unfortunately, the randomness associated with recombination has different mathematical properties to the random sampling of gametes (Figure 1). With background selection or hitchhiking, if an allele frequency increases in one generation, it is likely to inc...

The distribution of genetic variability in natural populations is the result of a number of evolutionary factors. We present concepts on the genetics of large populations, with special reference to association studies. Particular issues related to selection, mutation and genetic load, or migration in spatial models are not treated here. Genetic drift is assumed to be negligible, unless otherwis...