Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Lacy Robert C. Department of Conservation Biology, Daniel F.
Oxford Academic. A species with a broad distribution rarely has the same genetic makeup over its entire range. For example, individuals in a population living at one end of the range may live at a higher altitude and encounter different climatic conditions than others living at the opposite end at a lower altitude.
What effect does this have? At this more extreme boundary, the relative allele frequency may differ dramatically from those at the opposite boundary. Distribution is one way that genetic variation can be preserved in large populations over wide physical ranges, as different forces will shift relative allele frequencies in different ways at either end.
Migration is the movement of organisms from one location to another. Although it can occur in cyclical patterns as it does in birds , migration when used in a population genetics context often refers to the movement of individuals into or out of a defined population. What effect does migration have on relative allele frequencies? If the migrating individuals stay and mate with the destination individuals, they can provide a sudden influx of alleles.
After mating is established between the migrating and destination individuals, the migrating individuals will contribute gametes carrying alleles that can alter the existing proportion of alleles in the destination population.
How do populations respond to all these forces? As relative allele frequencies change, relative genotype frequencies may also change. Each genotype in the population usually has a different fitness for that particular environment. In other words, some genotypes will be favored, and individuals with those genotypes will continue to reproduce. Other genotypes will not be favored: individuals with those genotypes will be less likely to reproduce.
What type of genotype would be unfavorable? Unfavorable genotypes take many forms, such as increased risk of predation, decreased access to mates, or decreased access to resources that maintain health. Overall, the forces that cause relative allele frequencies to change at the population level can also influence the selection forces that shape them over successive generations.
For example, if moths with genotype aa migrate into a population composed of AA and Aa individuals, they will increase the relative allele frequency of a. However, if the aa genotype has a clear disadvantage to survival e. This page appears in the following eBook. Aa Aa Aa. Genetic variation describes naturally occurring genetic differences among individuals of the same species. This variation permits flexibility and survival of a population in the face of changing environmental circumstances.
Consequently, genetic variation is often considered an advantage, as it is a form of preparation for the unexpected. But how does genetic variation increase or decrease? And what effect do fluctuations in genetic variation have on populations over time? Mating patterns are important. Ultimately, no one study can validate the generality of a relationship between genetic diversity and population size.
Our current and future work on MNP reptiles must be replicated from taxonomically independent sets of closely related sympatric species sampled from a variety of different higher taxa. Moving forward, studies should also utilize next-generation sequencing technology in order to survey a large number of genes throughout the genome. This study of reptiles represents a single step in the process of resolving the evolutionary forces that maintain genetic diversity in natural populations.
Amos W, Harwood J. Factors affecting levels of genetic diversity in natural populations. Population size does not influence mitochondrial genetic diversity in animals.
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On the number of segregating sites in genetical models without recombination. Theor Popul Biol 7 : — Download references. J de la Torre was generous in providing his help with cloning. G Spicer and E Connor provided valuable comments and statistical advice. The comments of three anonymous reviewers greatly improved the manuscript.
You can also search for this author in PubMed Google Scholar. Correspondence to E J Routman. Supplementary Information accompanies this paper on Heredity website. Reprints and Permissions.
Hague, M. Does population size affect genetic diversity? A test with sympatric lizard species. Heredity , 92—98
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