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Molecular ecology is a field of evolutionary biology that is concerned with applying molecular population genetics, molecular phylogenetics, and more recently genomics to traditional ecological questions (e.g., species diagnosis, conservation and assessment of biodiversity, species-area relationships, and many questions in behavioral ecology). It is virtually synonymous with the field of "Ecological Genetics" as pioneered by Theodosius Dobzhansky, E. B. Ford, Godfrey M. Hewitt and others. These fields are united in their attempt to study genetic-based questions "out in the field" as opposed to the laboratory. Molecular ecology is related to the field of Conservation genetics.
Methods frequently include using microsatellites to determine gene flow and hybridization between populations. The development of molecular ecology is also closely related to the use of DNA microarrays, which allows for the simultaneous analysis of the expression of thousands of different genes. Quantitative PCR may also be used to analyze gene expression as a result of changes in environmental conditions or different response by differently adapted individuals.
Molecular ecological techniques have recently been used to study in situ questions of bacterial diversity. This stems from the fact that many microorganisms are not easily obtainable as cultured strains in the laboratory, which would allow for identification and characterisation. It also stems from the development of PCR technique, which allows for rapid amplification of genetic material.
The amplification of DNA from environmental samples using general of group-specific primers leads to a mix of genetic material that has to be sorted out before sequencing and identification. The classic technique to achieve this is through cloning, which involves incorporating the amplified DNA fragments into bacterial plasmids. More recent techniques such as temperature gradient gel electrophoresis, allow for a faster result.