Phylogeography of the wild subspecies of Zea mays

Z. mays ssp. parviglumis and ssp. mexicana are the closest wild relatives to domesticated maize. Using isozyme and chloroplast evidence, this study examined how populations of these subspecies are related to one another, and how geography has structured the relationships between them. As some lines of evidence indicate that ssp. mexicana is a derived clade of ssp. parviglumis, dispersal, isolation by distance (IBD), and altitudinal hypotheses were tested to explain the genetic differentiation of ssp. mexicana and parviglumis populations. Simple dispersal hypotheses explained most of this genetic variation, while IBD and altitudinal models explained very little of the variation. The origin of this dispersal appeared to be the middle and lower elevation regions of Guerrero. These dispersal events are discussed in light of Late Pleistocene and Holocene climate change and maize domestication.