|TAKUNO, SHOHEI - University Of California|
|RALPH, PETER - University Of California|
|SWARTS, KELLY - Cornell University - New York|
|ELSHIRE, ROB - Cornell University - New York|
|GLAUBITZ, JEFFREY - Cornell University - New York|
|Buckler, Edward - Ed|
|HUFFORD, MATTHEW - Iowa State University|
|ROSS-IBARRA, JEFFREY - University Of California|
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2015
Publication Date: 6/15/2015
Citation: Takuno, S., Ralph, P., Swarts, K.L., Elshire, R.J., Glaubitz, J.C., Buckler IV, E.S., Hufford, M.B., Ross-Ibarra, J. 2015. Independent molecular basis of convergent highland adaptation in maize. Genetics. 200(4):1297.
Interpretive Summary: Maize has adapted to environments from Northern Europe, the US, the tropics, and Andes. This tremendous adaptation has allowed maize to become the highest production crop in the world. But how, on the DNA and evolutionary process level, does adaption occur? Does adaptation occur through new mutations or through the sharing and migration of old mutations? By applying a combination of genomic data from diverse landraces of maize and simulations, this study was able to show that shared old genetic variation appears to be most important for adaptation. This has important implications for climate change, as it suggests adapting maize to future environments will likely have to rely on the genetic variation that has already been around for thousands of years and stored in our germplasm banks.
Technical Abstract: Convergent evolution is the independent evolution of similar traits in different species or lineages of the same species; this often is a result of adaptation to similar environments, a process referred to as convergent adaptation. We investigate here the molecular basis of convergent adaptation in maize to highland climates in Mesoamerica and South America, using genome-wide SNP data. Taking advantage of archaeological data on the arrival of maize to the highlands, we infer demographic models for both populations, identifying evidence of a strong bottleneck and rapid expansion in South America. We use these models to then identify loci showing an excess of differentiation as a means of identifying putative targets of natural selection and compare our results to expectations from recently developed theory on convergent adaptation. Consistent with predictions across a wide parameter space, we see limited evidence for convergent evolution at the nucleotide level in spite of strong similarities in overall phenotypes. Instead, we show that selection appears to have predominantly acted on standing genetic variation and that introgression from wild teosinte populations appears to have played a role in highland adaptation in Mexican maize.