A test of ecological and ethnolinguistic determinants of maize diversity in southern Mexico

While prevailing theories of crop evolution suggest that crop diversity and cultural diversity should be linked, empirical evidence for such a link remains inconclusive. In particular, few studies have investigated such patterns on a local scale. Here, we address this issue by examining the determinants of maize diversity in a local region of high cultural and biological richness in Southern Mexico. We collected maize samples from Mixtec and Chatino villages at low and mid elevations. Although morphological traits show few patterns of population structure, we see clear genetic differentiation among villages, with ethnicity explaining a larger proportion of the differentiation than altitude. Consistent with an important role of ethnicity in patterning seed exchange, metapopulation model-based estimates of differentiation match the genetic data within village and ethnic group, but dramatically underestimate differentiation when all four villages are taken together. Our research provides insights about the importance of social origin in structuring maize diversity at the local scale.