Artificial selection, also known as selective breeding, is a long-established method for exploring genetic variation and different adaptive phenotypes in a population. New experimental designs in evolutionary biology can combine this method with genetic sequencing to probe the mechanisms that underlie adaptive and evolutionary processes. With the growing availability of new sequencing techniques, researchers can now sequence multiple and diverse populations of organisms for a single study.

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The evolve and resequencing (E&R) method is an increasingly popular study design that combines classic selection experiments with pooled genetic sequencing to quantify the genetic differences that accumulate after generations of selection. Mateusz Konczal (Jagiellonian University, Kraków, Poland) and colleagues recently used an E&R design to compare populations of wild-derived bank voles after artificially selecting one population for higher aerobic metabolic performance (Mol. Biol. Evol. doi:10.1093/molbev/msv038; published online 3 March 2015). After 13 generations, voles from selected lines achieved a 48% higher peak rate of oxygen consumption when swimming and showed a suite of other behavioral and physiological differences that distinguished them from a control population.

Konczal's use of wild-derived voles sets this study apart from other E&R studies that frequently use model or domesticated lineages to explore genetic changes during artificial selection. While specific studies can benefit from controlled variation and the context of prior research, the inbred gene pools of model and domesticated lineages can limit the applicability of such studies to natural systems. “Our study differed from many other E&R studies (especially these performed on vertebrates) in the nature of the standing genetic variation available at the onset of the experiment,” the authors noted, a characteristic they hoped would more closely model the dynamics of a natural vertebrate population.

Perhaps owing to this standing genetic variation, when Konczal's team sequenced each lineage of voles, they found very few differences in genes and allele frequencies between lines. Instead, they discovered, it was gene expression that differed. The authors identified 79 genes in the heart and 278 in the liver as differentially expressed between the two populations (no other organs were sampled). With very few genetic changes, short-term adaptation occurred largely within existing genetic variation through non-genetic changes, such as metabolic, hormonal and epigenetic modifications. “The results show that remarkable evolution of physiological performance can occur by regulatory changes within basically the same biochemical machinery,” said Konczal in a press release. Where adaptation is concerned, these results also demonstrate the flexibility and resilience of a healthy and diverse gene pool in the face of strong selective pressures, artificial or otherwise.