Genetic evidences of natural selection

Abstract

Perfectti, F., Picó, F.X., Gómez, J.M. (2009). Genetic evidences of natural selection. Ecosistemas 18(1):10-16.

Natural selection is one of the main factors driving the evolutionary process and the only one leading to adaptations. Selection acting on a population can be detected by quantifying the relationship between individual phenotype and relative fitness. However, detecting the effect of past selection is not possible by only using an ecological approach. To cope with this issue, several molecular evolutionary genetics methods have been developed during the last 40 years. A first group of tests use the quasi neutral theory of molecular evolution as null model, and assume the occurrence of selection when the observed outcome significantly departs from the expectations under neutral evolution. Some tests, such as Tajima’s D, dN/dS ratio, MK test or HKA test, can determine the kind of selection acting on populations, but are unable to quantify its intensity. The analysis of selection based on Poisson Random Fields (PRF) overcomes this caveat. A second group of analyses infer selection by comparing the amount of genetic variation in quantitative traits (QST) against the amount of neutral genetic variation (FST). Lastly, one of the most recent and promising methods to explore natural selection is related with the superb advance in genomics. Although we are still far from fully appreciate the importance of this tool, we believe that the use of the genomics will produce a qualitative enhancement in our understanding of the importance of natural selection in the wild.