A single domestication for maize shown by multilocus microsatellite genotyping

Abstract

There exists extraordinary morphological and genetic diversity among the maize landraces that have been developed by preColumbian cultivators. To explain this high level of diversity in maize, several authors have proposed that maize landraces were the products of multiple independent domestications from their wild relative (teosinte). We present phylogenetic analyses based on 264 individual plants, each genotyped at 99 microsatellites, that challenge the multiple-origins hypothesis. Instead, our results indicate that all maize arose from a single domestication in southern Mexico about 9,000 years ago. Our analyses also indicate that the oldest surviving maize types are those of the Mexican highlands with maize spreading from this region over the Americas along two major paths. Our phylogenetic work is consistent with a model based on the archaeological record suggesting that maize diversified in the highlands of Mexico before spreading to the lowlands. We also found only modest evidence for postdomestication gene flow from teosinte into maize.

Traditional Mexican Agricultural Systems and the Potential Impacts of Transgenic Varieties on Maize Diversity

“…Molecular data indicate that Mexican maize diverged from Mexican annual teosinte (Z. mays ssp. parviglumis) between 5,689 and 10,093 BP (Matsuoka et al, 2002), which is consistent with the date of the oldest fossil maize of 6,250 BP (Piperno and Flannery, 2001). The early diversification probably occurred in the highlands between the present-day states of Oaxaca and Jalisco, before maize spread into the lowlands (Matsuoka et al, 2002).…”

“…In a recent analysis using molecular markers, Matsuoka et al, (2002) found that races of maize are differentiated at the continental level according to an isolation-bydistance scheme, in which the races that are the farthest apart geographically are also the most genetically distinct. At the country level (in Mexico, for example), the genetic relationships between races of maize are not very clear or well defined, possibly because ''most of the isozyme (and this can be true for other markers) variation in the races of maize in Mexico occurs within, rather than between races'' (Sanchez et al, 2000: 57).…”

Integrating the processes in the evolutionary system of domestication

“…Genome-wide based evidence resoundingly supported the notion on single origins for many crops (e.g. Heun et al, 1997, Badr et al, 2000, Matsuoka et al, 2002 by producing phenograms in which domesticated crops were monophyletic. This data was sometimes in conflict with single gene evidence, such as in the case of barley, which became awkward anomalies to what was largely taken as genetic support for the rapid transition paradigm, and a picture of explosive expansion of agriculturalists out of the centres of origin.…”

Population genetic structure of two primary parasitoids of Spodoptera frugiperda (Lepidoptera), Chelonus insularis and Campoletis sonorensis (Hymenoptera): to what extent is the host plant important?

“…Spodoptera frugiperda itself also shows evidence for host race formation, specializing on either maize or rice races in the USA (Nagoshi & Meagher 2008). Maize is a crop on which S. frugiperda and its parasitoids have co-occurred for several thousand years in Mexico (Matsuoka et al 2002), thus representing one of the longest associations between a crop plant and associated insects. Sorghum was introduced during the mid-1800s (Smith & Frederiksen 2000), giving ample time for the insects to adapt and specialize.…”