Evolution and Climate Change in the Oceans
Migration, or gene flow, is defined as "the transfer of alleles from the gene pool of one population to the gene pool of another population" (Freeman, Herron 225). It is used in a more familiar sense of the word as meaning a periodical movement of individuals.
In a paper published by Whitlock and McCauley (Nature 1999), the scientists describe the methods used for measuring gene flow. The difficulty of actually measuring gene flow led to the development of indirect measures through extrapolation from genetic frequency data. The measurements are described as variants of Fst, the measure of variance in populations, and the scientists used them to find Nm, or the number of migrants successfully entering a population per generation. They concluded that because this model makes "biologically unrealistic" assumptions, the information produced is essentially limited data about dispersal inferred from gene frequency data.
Scientists Ayre and Hughes used these methods to study the genotypic diversity and gene flow in several species of coral in order to predict how these species might adapt (or fail to adapt) to climate change (Ecology Letters 2004). They concluded that genetic diversity varies greatly between coral species. The species S. hystrix was found to have low gene flow among local sites and regional sites. This species also had low genetic diversity, and thus the scientists inferred that this species was descended from a very small population initially. Surprisingly, S. hystrix has a very large geographic range. Another species that they studied, S. pistillat
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