Evolutionary Responses to a Constructed Niche: Ancient Mesoamericans as a Model of Gene-Culture Coevolution

Hünemeier, Tábita; Amorim, Carlos Eduardo Guerra; Azevedo, Soledad; Contini, Veronica; Acuña-Alonzo, Víctor; Rothhammer, Francisco; Dugoujon, Jean-Michel; Mazières, Stephane; Barrantes, Ramiro; Villarreal-Molina, María Teresa; Paixão-Côrtes, Vanessa Rodrigues; Salzano, Francisco M.; Canizales-Quinteros, Samuel; Ruiz-Linares, Andres; Bortolini, Maria Cátira

Our neutral demographic simulation analysis showed results in the same direction. The region containing the ABCA1*230 polymorphism and 19 flanking SNPs presented a slightly lower average heterozygosity than the putative neutral region dataset (0.32 vs. 0.34 respectively); but global and pairwise F ST were higher for the ABCA1 region (global F ST 0.03 vs. 0.01; average pairwise F ST 0.05 vs. 0.01). Considering that both genomic regions were studied using the same quantity of markers and the same sampling strategy, in populations that were subjected to the same demographic history, the observed differences may occur due to diverse factors, one of them being natural selection. To test this hypothesis each dataset, summarized by the above-mentioned statistics, was also compared to each of 100,000 neutral simulations by means of Euclidian distances. The empirical dataset containing the ABCA1*230 polymorphism presented a poorer fit to neutrality than the putative neutral region dataset, showing Euclidian distances that were twofold higher than those of the neutral simulations (70.64 vs. 35.12) . Interestingly, when the Mesoamerican agriculturalist subdivision was excluded from the analysis, this difference dramatically decreased (45.80 vs. 35.12). Thus, the poor fit to neutrality observed at the ABCA1*230 site and its flanking regions may be associated with the genetic pattern found in Mesoamerica.