Individuals of a particular species can develop local adaptations when they are more fit (better suited to survive and produce viable offspring) than other individuals. Selection pressures will favor desirable traits that are better suited to the environment and allow organisms with these local adaptations to pass on their genes to future generations. Over time natural selection will favor the versions of genes that encode advantageous physical traits, causing the adaptation to establish in local populations.

Recent work by a team of researchers, including Assistant Professor Katie Lotterhos discusses why mapping the genetic loci (locations of the different versions of a gene) is essential to understanding the evolutionary process of local adaptation.

In the study, recently published in the journal The American Naturalist, Lotterhos and colleagues evaluate different methods to identify locally adaptive loci.  The researchers review two common approaches: differentiation outlier methods (that identify genetic difference among members of a population) and genetic-environment association methods (that identify a link between genetic differences of a population and the environment in which it occurs).

These approaches sample the genetic makeup of populations and construct models to calculate F_ST, or the proportion of genetic variance in one subpopulation relative to the total genetic variance – large F_ST values indicate a greater degree of differentiation between populations. However, several factors can distort the F_ST, such as the presence of a harmful mutation, which decrease fitness regardless of environmental factors, and biased sampling of subpopulations with disproportionate genetic differences unrepresentative of the total population.

Due to these challenges, it can be difficult to identify which loci are responsible for endowing certain subpopulations with local adaptations. However, the study’s authors offer solutions such as developing whole genome resequencing methods to identify the smallest regions responsible for local adaptation. Additionally, developing accurate scales for how the environment affects fitness will aid in pursuits to understand the genetic basis of local adaptation.