Teosinte phylogeography

• PHYLOGEOGRAPHY OF THE WILD SUBSPECIES OF ZEA MAYS, Edward S. Buckler IV, Major M. Goodman, Timothy P.Holtsford , John F. Doebley, and Jesus Sanchez G. In review for Evolution.

ABSTRACT

Z. mays ssp. parviglumis and ssp. mexicana are the closest wild relatives to domesticated maize. This study examined how the populations of these subspecies are related to one another, and how geography has structured the relationships between these populations. Isozyme and chloroplast evidence was the focus of this analysis. Some lines of evidence indicated that ssp. mexicana is a derived clade of ssp. parviglumis. Clinal and dispersal hypotheses were tested to explain the genetic differentiation of ssp. mexicana and parviglumis populations. Simple dispersal hypotheses explained most of the genetic variation, while clinal hypotheses explained very little of the variation. The origin of this dispersal appeared to be the lowland regions of Guerrero. There is also evidence for secondary hybridization and dispersal events. These dispersal events are discussed in light of Late Pleistocene and Holocene climate change and maize domestication.

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Figure 1. Distribution of Z. m. ssp. parviglumis (black circles) and mexicana (black squares) populations and the basic disperal hypothesis. Four populations are far outside the range of this map: JD55 and JD56 are in Nabogame, JD45 is in Durango, and CS02 is in Oaxaca. Regions above 1600m are shaded gray; this may have been the maximum altitude for teosinte growth at 18,000BP. The lines indicate the dispersals in the basic dispersal model, while the locations of the postulated ancestral nodes are indicated by a single letter (A…I).