![]() Speciation with gene flow could be common. P.The multifarious effects of dispersal and gene flow on contemporary adaptation. Understanding the evolution and stability of the G-matrix. Effects of migration on the genetic covariance matrix. The maintenance (or not) of polygenic variation by soft selection in heterogeneous environments. When sources become sinks: migrational meltdown in heterogeneous habitats. A framework for comparing processes of speciation in the presence of gene flow. Disentangling interactions between adaptive divergence and gene flow when ecology drives diversification. A mathematical theory of natural and artificial selection. Incipient speciation by divergent adaptation and antagonistic epistasis in yeast. Animal Species and Evolution (Harvard Univ. Evidence for ecological speciation and its alternative. On the tendency of species to form varieties and on the perpetuation of varieties and species by natural means of selection. It further highlights that adaptive trajectories are governed by complex interactions of gene flow, ancestral variation and genetic correlations.ĭarwin, C. This evolve-and-resequence experiment shows that rapid ecological differentiation can arise even under high rates of gene flow. Multiple loci showed consistent evidence for antagonistic pleiotropy across migration treatments providing a conceptual link between adaptation and divergence. In sympatry, divergence was mainly mediated by novel mutations enriched in a subset of genes and was characterized by the repeated emergence of two strategies: an ecological generalist and an asexual growth specialist. In allopatry, adaptive divergence was mainly conferred by standing genetic variation and resulted in ecological specialization. The evolution of some fitness components was constrained by pervasive negative correlations (trade-off between asexual growth and mating), while others changed direction under the influence of migration (for example, survival and mating). This effect was apparent across central life-history components (survival, asexual growth and mating) but differed in magnitude between ancestral genetic backgrounds. Contrary to theoretical expectations, adaptive divergence was most pronounced when migration was either absent (allopatry) or maximal (sympatry), but was much reduced at intermediate rates (parapatry and local mating). To address this question, we subjected 132 sexually reproducing fission yeast populations, sourced from two independent genetic backgrounds, to disruptive ecological selection and manipulated the level of migration between environments. Yet, the conditions under which it can arise in the presence of gene flow remain contentious. Hypothesis: Repeated natural disasters will yield different population genetic structures therefore, each time this experiment is run, the results will vary.Adaptive divergence is the key evolutionary process generating biodiversity by means of natural selection. This phenomenon is known as the bottleneck effect. ![]() As a result, the genetic makeup of the population can change dramatically. Question: How do natural disasters affect the genetic structure of a population?īackground: When much of a population is suddenly wiped out by an earthquake or hurricane, the individuals that survive the event are usually a random sampling of the original group. Scientific Method Connection: Testing the Bottleneck Effect As a result, the population expresses unusually high incidences of Huntington’s disease (HD) and Fanconi anemia (FA), a genetic disorder known to cause blood marrow and congenital abnormalities-even cancer. This is likely due to the fact that a higher-than-normal proportion of the founding colonists carried these mutations. The founder effect is believed to have been a key factor in the genetic history of the Afrikaner population of Dutch settlers in South Africa, as evidenced by mutations that are common in Afrikaners but rare in most other populations. The founder effect occurs when the genetic structure changes to match that of the new population’s founding fathers and mothers. In this situation, those individuals are unlikely to be representative of the entire population, which results in the founder effect. \( \newcommand\): A chance event or catastrophe can reduce the genetic variability within a population.Īnother scenario in which populations might experience a strong influence of genetic drift is if some portion of the population leaves to start a new population in a new location or if a population gets divided by a physical barrier of some kind.
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